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Old 04-10-2008, 10:19 AM   #1
CanisLupusArctos
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Default 2008 Spring Flood Situation

This thread is for flood information & discussion as the spring meltdown finally appears to be kicking into high gear.

We start with about a foot of dense snow on the ground around the lake, which is a lot better than the situation we had 3 weeks ago but still more threatening than last year at this time.

Of greater concern is what's in the mountains (more snow than anyone has seen there in decades.)

The last couple days have been in the 50s which has accelerated melting of the snow. The lake level has responded but so far the dam seems to be letting it out fast enough to prevent rapid rising of the lake.

Coming this weekend we have a possible major rain storm on the way for both days, and the next several days look wet. At the moment, however, it looks like we might get spared from flooding by something no one really wants to see more of.

It appears the storm is going to give us more of its cold side than warm side this weekend. If this situation pans out, it will spare us the heaviest rainfall on its warm side while keeping temps in the mid-30s... these near-freezing temps would keep snow from melting quickly enough to push the area's rivers above flood stage this weekend.

At the same time it may produce snow above 1500' elevation (just below Mt. Major's summit.) This would definitely keep rapid snowmelt from occurring in the Mountains.

Even with this less-rainy side of the storm, we may still get an inch of rain below 1500', so we're still very close to a flood situation for this weekend. Therefore it would be a good idea to keep watching weather reports in case flooding suddenly starts to look more likely.

Beyond this weekend I think we'll still be walking a fine line between "flood" and "no flood" (especially on the area's rivers and streams) until the spring melt has passed its max.

If the rivers downstream of Winnipesaukee's dam approach flood stage, we may see the dam drastically reduce outflow, which could cause a rapid rise in lake level. I don't think it would take much more than an inch of widespread rain to make that happen, especially if combined with warm temps. We also need to watch rainfall amounts for south of the lake, because if the area from Concord-southward gets a rainstorm heavy enough to cause river flooding there, it might necessitate the closing of Winni's dam.
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Old 04-10-2008, 10:57 AM   #2
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Thanks CLA - did anyone's basement flood yet? I'm stuck in IL so can't check and mine always floods this time of year. If someone else has water then I definitely do as well.
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Old 04-10-2008, 01:46 PM   #3
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Originally Posted by CanisLupusArctos View Post
If the rivers downstream of Winnipesaukee's dam approach flood stage, we may see the dam drastically reduce outflow, which could cause a rapid rise in lake level. I don't think it would take much more than an inch of widespread rain to make that happen, especially if combined with warm temps. We also need to watch rainfall amounts for south of the lake, because if the area from Concord-southward gets a rainstorm heavy enough to cause river flooding there, it might necessitate the closing of Winni's dam.
Nervously watching the Merrimack outside my window in Manch.The current height is at 9 ft at Goffs Falls station.Projected height on Saturday is 10 ft or 1 foot below "action stage".Flood stage is at 11 ft.Been flooded the last 2 years and am not looking forward to a 3rd.
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Old 04-10-2008, 02:25 PM   #4
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Nervously watching the Merrimack outside my window in Manch.The current height is at 9 ft at Goffs Falls station.Projected height on Saturday is 10 ft or 1 foot below "action stage".Flood stage is at 11 ft.Been flooded the last 2 years and am not looking forward to a 3rd.
I noticed the river to be running a bit high the last few days, but nothing unusual...yet. I go by the "no-wake" sign on the bridge support in Hooksett. If I can still see it, it is not at flood stage. Once that sign gets underwater, watch out down stream.
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Old 04-10-2008, 02:29 PM   #5
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According to the National Weather Service's Gray, Maine folks at 1:30 PM today the storm is likely to impact the area between Merrimack and Rockingham counties the most - with up to an inch of precipitation between 2PM on Friday and 8AM on Sunday. After this batch of weather it looks dry (but not overly warm) for the next 7 to 10 days.

Given this info, and since the big lake is a bit below normal for this time of year, flows have been eased a bit to help the lower lakes and river segments deal with the current melting and runoff expected from the rain over the next few days. We know that, as of 4/8, the snow pack in the basin has about about 1.6 times the normal water content for early April - but again, there is a bit of room in the lake and the forecast is for dry conditions next week.

As a rule of thumb, for every 230 cubic feet per second (CFS) of flow difference between inflow to the lake and the discharge at Lakeport Dam the level of the lake will change by 0.01 feet (less than 1/8th of an inch) every 24 hours. We've reduced flows by 400 cfs in the last 2 days so the lake will rise about 3/16th of an inch more for each 24 hour period into the future. With the ongoing melt the lake will likely rise more than that for the next several successive days - but our management over the last 2 days has added a 3/16th of an inch "surcharge" to whatever Mother Nature does.

As always, we have our eye on both the forecast and the real-time conditions in the basin.
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Old 04-10-2008, 03:50 PM   #6
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Keeper - thank you for the information. You mentioned that for every 230 CFS of flow difference between the inflow to the lake and the discharge at the Lakeport Dam, the lake rises .01 feet every 24 hours. My question is how you quantify what the inflow to the lake is. I have always wondered about this since there must be a lot of variables (precipitation, snowmelt, soil moisture, etc.).
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Old 04-10-2008, 05:02 PM   #7
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Default question for CLA

CLA, you indicated that in the mid 30's we could expect rain but at 1,500 feet it would likely be snow. I have always wondered what the convertion factor is for calculating temperature at various altitudes. During the winter I try to estimate the temperature/percipitation (hopefully snow) on Gunstock based on the forecast for Gilford. Assuming the temperature in Gilford is 35 (@ 500ft), what would the temp be at midway up Gunstock (1,000 ft) & at the top (1,950 ft). - is there a rule of thumb you could share?
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Old 04-10-2008, 07:52 PM   #8
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Default 3 degrees per thousand feet

In aviation, the formula is 3 degrees per 1000'. Near ground level, there may be other factors.

Today was a real melt day! Water running everywhere.
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Old 04-10-2008, 09:39 PM   #9
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CLA - I learn so much from you! Thanks for contributing so much easy-to-understand information. You are a terrific asset to this forum.

Keeper - great to know that, as usual, you guys are on top of the situation.
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Old 04-10-2008, 11:38 PM   #10
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Default NE Weather is outside the box half the time

Lakegeezer has the general formula. That's under normal conditions, a typical fair weather day with warmest air near the ground and cooler as you go up.

Apart from that, this is New England which means there is no formula! I say this with laughter but it's true. We get those days when the "Basic Physics" textbook is right (usually when nothing is happening,) but it seems every time a storm comes, its prediction requires breaking out the "Advanced Physics" textbook. A certain percentage of those storms require changing the textbook for a blank notebook + pen. Those are the days when God looks at the wee professors and says "Ok listen up people!!!"

Every time I travel far away I see more "Basic Physics" days than anything else. Then as I get close to New England on the way home I can often hear a certain heavenly voice ahead in the distance saying, "okay listen up people!"

To get an idea of how varied our vertical temp profile can be in New England, go to the Mount Washington Observatory site (look for the Auto Road temp profile) or the AIRMAP site on a regular basis just to see what the temps are, at different altitudes.

On at least a couple of occasions I've climbed Mt. Washington in winter, starting off in the cold, finding above-freezing temps at mid-mountain, and arriving at the summit to find the same temperature as at the base. One time, as a blizzard was clearing, we went above the clouds at 4,000 feet and arrived at the summit to find warmer temps than at the base. Most winter storms DON'T do that... but that one did. The models had a good handle on it, so we were actually expecting it (but ready to turn back, just in case.) Weather around here can be so outside-the-box!

One thing the forecasters at the NWS said in their discussion yesterday was that the situation coming up this weekend (I'll spare you the technical terms) has a long track record of confusing the living daylights out of computer models and human forecasters. It doesn't have to mean the storm will be powerful, just complicated from a forecaster's perspective (or as a surgeon would say sometimes the smallest operations end up causing them the biggest headaches... same thing.) Whenever that happens it means it's time to consult your great-grandfather's farm journal for advice on predicting it. And all the while, those poor TV guys still have to smile like flight attendants and act like they have it all figured out.

Here's the storm as depicted on the Thursday night watch & warning map. Look at how many different types of weather there are! And a few of them aren't even supposed to be where they are in mid-April. The blue and red boxes are severe thunderstorm and tornado watch boxes. Everything else is in the map legend.

Keeper, are you with the DES dam operations?
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Old 04-11-2008, 07:17 AM   #11
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Default Question

For CLA, Keeper and all,

Are we headed for another very high lake spring this year. Can we assume that most docks will be under water at the start of the season? It all seems pretty unavoidable at this time. I recall lots of debris in the water last time.
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Old 04-11-2008, 07:32 AM   #12
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Long Pine,
The drainage area of Lake Winnipesaukee does not lend itself very well to efficient inflow gaging. Though there are a few significant feeder streams - like the Merrymeeting River - the basin is so large that trying to generalize conditions for the whole basin by what is happening in the Alton/New Durham area doesn't work well. We've tried using gages at Poorfarm (Gunstock) and Shannon (Ossipee Mountains) brooks, but again we found that we were really only measuring conditions in a very small area.

What we do is use the change in lake elevation as measured at the Weirs Beach gage and the discharge at Lakeport Dam to estimate basin inflow.

inflow = (change in lake level (in hundredths of feet) X 230 cfs) + discharge at Lakeport

Example for a rising lake - yesterday to today:
level on day1 = 503.33
level on day2 = 503.43
ave. outflow at Lakeport between 7AM yesterday and 7AM today = 1017 cfs

Estimated average inflow between day1 and day2 is:
(+10x230) + 1017 = 3317 cfs

If the lake had fallen by 3 hundredths then inflow is about:
(-3x230) + 1017 = 327 cfs

If the lake is steady from one day to the next then inflow = outflow.

Though this method is approximate and doesn't provide us with "real-time" inflow values it is very useful, when combined with forecast information, in establishing inflow trends and guiding management decisions. As you state, other variables like snow melt, precip. and soil moisture can make a huge impact on inflow trends. The basin is ripe at this time of year, in general, and the water content in the current snow pack this spring is above normal.
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Old 04-11-2008, 10:28 AM   #13
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Default Keep your eyes on the rivers

The National Weather Service has issued a flood watch for the possibility of flooding on rivers this weekend. We may all have our eyes on the lake but I should have emphasized earlier that I'm more concerned about rising rivers this spring, than I am about rising lake.

On lake flooding...

Let's not forget that last year's high lake level happened as a result of the April 16 NorEaster. I left to go to work in the mid-afternoon and the lake was about 10 inches below the dock. When I came back in late evening the water was licking at the underside of the dock. The next morning, the dock was underwater. It rose about a foot in just a couple of days.

That storm dropped 2.78 inches of rain over the course of three days. The greatest fell on the 16th, with 1.90 inches of rain. Snowcover at the start of the storm was 1 inch. The winter had brought 9.71 inches of rain/melt until that point.

This year we have 10 inches of snow on the ground (as of yesterday). The winter has brought 14.76 inches of precip from Dec. 1 until today, although I don't know how much of that has already passed downstream.

This data hints that it probably wouldn't take a storm as big as last year's to create a similar problem. BUT, as Keeper said, it's hard to monitor the inflow of the lake because it's not like it comes in through just one source... this lake gets its water from a million different little sources and probably a few that Indiana Jones hasn't found yet.

There's very little reason (in the big scheme of things) to fret over a very-high lake level, because neighborhoods and highways don't get washed away by Lake Winnipesaukee. The lake floods pass, and we get right back to normal.

In the most recent floods (Oct 2005, May 2006, April 2007) the lakes region and the rest of the state lost several roads to washouts from swollen streams and rivers. Dams were threatening to go. Dover NH came verrrryyy close to losing their Central Ave Bridge downtown. People got swept away and died. Recycle bins from the Manchester area washed up on the Massachusetts coast along with everything else that had been in people's yards. Some people along the state's rivers are still rebuilding or repairing. For that reason, NOAA, FEMA and others are directing their flood concerns toward the state's rivers. Most of the problems associated with our high lake level don't mean much when we can't even get to the lake or around the area because the roads are washed out.

The rivers, not the lake, are also where taxpayers should be most concerned: Roads are made from oil, using heavy equipment that burns a lot of fuel, and the price of oil keeps soaring into record territory.

--> Answer to Hazelnut: Last year's lake debris was more a result of wind from the April 16 storm and not so much the flood. Prior to the storm, the ice wasn't ready to go soon. During the storm, my station had wind gusts to 50 mph for 18 hours. We maxed out with a sustained wind of 45 mph and gust to 64 mph. This violently broke up the ice which was still mostly solid, clear, 6-12" thick. I watched bergs of it float by during the storm, crash into shoreline structures, and carry debris away. It was incredible to watch, along with the trees falling. The shoreline got pummeled in that event, by air and by iceberg. The result was a lot of stuff floating around in the lake after the storm ended.

Last edited by CanisLupusArctos; 04-11-2008 at 10:43 AM. Reason: Answer Hazlenut's question
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Old 04-11-2008, 11:42 AM   #14
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Default The Mighty Merrimack in Haverhill MA

Is running fast - as it should - it's spring afterall - but we are at 3 and half feet below flood in Haverhill MA as of this morning! Still folks along the river are concerned - this would be the third year in a row for floods should the snowmelt occur to quickly. Good news is - we have no snow down here and - so the river should be relatively forgiving to this region!
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Old 04-11-2008, 12:11 PM   #15
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Good news is - we have no snow down here and - so the river should be relatively forgiving to this region!
I wouldn't be too comfortable with that good news.You did not have snow in that area the last 2 years either and this year the snowpack in the north is much greater.It really comes down to how much rain/warm temps are recieved in a what period of time.Right now the Merrimack in Manchester is 18 inches below "action stage".It is forecast to be at action stage sometime on Saturday.Watching nervously from the riverbank right now.My mill building will flood after 5 ft above flood level so I'm in better shape than a lot of people.
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Old 04-11-2008, 09:35 PM   #16
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Default True - well actually not really true...

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I wouldn't be too comfortable with that good news.You did not have snow in that area the last 2 years either and this year the snowpack in the north is much greater.
Two years ago when the big floods hit - we did have late snow and the ground was saturated and we received 14 or 15 days of straight heavy rains - this year - the ground is relatively dry - not at or near saturation point and since our snowpack melted gradually, there was time for maximum absorption. Remember we recv'd something in the are of 15 inches of rain in 2006 and last year about 11inches of rain - in a very short span. Nothing like that is predicted.
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Old 04-12-2008, 02:57 AM   #17
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Question Dam People, Waterproofing Dock Spiders

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"...The next morning, the dock was underwater. It rose about a foot in just a couple of days..."
Doncha' hate it—watching the dock spiders race from your dock to your shore?

A little off-topic, but...

Seriously, our "permanent" docks are getting weakened not just by ice at low water, but by waves while the docks are under water. But what can be done about the dock's waterproofing that's going away with more frequency?

Because of a skin sensitivity, volunteers spread the stuff for me every other year; however, year by year, I'm waving them off—also with more frequency.
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Old 04-12-2008, 02:59 PM   #18
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The National Weather Service just issued a flood warning for the Connecticut River at West Lebanon from now until Sunday night.

Rapid snow melt has brought the river to 16.7 feet (flood stage is 18 feet) and they are expecting a crest of 19 feet between now and Sunday night.

While not part of the Winnipesaukee watershed, it is a result of snow melt from up north, and therefore may be a sign of things to come.

It's starting to look like we might get temps in the 60s in the Wed-Fri timeframe. At this time of year, abnormally warm temperatures (75+) are not unusual, but are often not predicted until the day before. Usually the season's first 80-degree day starts off as a much cooler forecast and gradually gets warmer as the day approaches. Forecasters are usually unwilling to commit to a summery temp forecast at this time of year until it's right on the doorstep and knocking.

Last April, even after the way-below-normal temps we had from late January to early April, we still had a 76-degree day on April 23 (many parts of NH were in the low 80s.) Between the 21st and 24th the daytime highs were 66... 64... 76... 65. Such an occurrence this year could generate a lot of water from the snow upstream.

You probably wouldn't have more than 24 hours' notice of such temps... so best prepare as though the mountains were going to be in the 70s tomorrow and then you'll be ready for any flooding if it does happen before most of the snow melts. Watch the weathermap for warm fronts. They're common at this time of year as warm air makes its annual northward push from the Gulf of Mexico. Warm fronts can generate several hours of steady precip, followed by a sudden jump in temps after they pass.
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Old 04-13-2008, 11:27 AM   #19
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Default 04/13 Sunday 12:25pm

River Flood Statement
National Weather Service Gray, Me
951 Am Edt Sun Apr 13 2008

...the Flood Warning Is Cancelled For The Following River In New
Hampshire And Vermont...

Connecticut River At West Lebanon Affecting Grafton...sullivan And Windsor Counties


National Weather Service Taunton Ma
1120 Am Edt Sun Apr 13 2008

...the Flood Warning Is Cancelled For The Following Rivers In
Connecticut...massachusetts...

Connecticut River At Thompsonville Affecting Hartford And Hampden Counties

...the Flood Warning Continues For The Following Rivers In
Connecticut..
Connecticut River At Hartford Affecting Hartford And Middlesex
Counties
Connecticut River At Middletown Affecting Hartford And Middlesex Counties

Continued Runoff From Snow Melt In Central And Northern New
England...combined With The Rainfall From Friday Night And
Saturday...will Keep The Lower Connecticut River In Minor
Flood At Hartford And Middletown Connecticut...probably Into
Tuesday...if Not Longer.
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Old 04-13-2008, 04:32 PM   #20
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Default Dock

Our dock has been right at lake level the last couple springs, last year it was covered with about 2" of water. The waves did structural damage to it and we have major repairs scheduled for this season. It appears that the lake has come up about 4" since I measured Thursday. I'm expecting the dock to be under water again real soon (another 20"). We're considering raising the dock another 12" just in order not to deal with this each season.
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Old 04-14-2008, 10:32 AM   #21
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Default Looking pretty good?

Except for the Merrimack at Concord (above flood stage) and Manchester (very near flood stage) most of the river gages show that the levels are declining, including the Pemigewasset and Winni Rivers. I live along the Merrimack in Hudson and the levels are at normal spring highs, up a little after the weekend rain but OK. The lake level is about where it should be for this time of year. The forecast for the next 10 days at the lake is for almost no rain and temps in the 50's to low 60's, nightime around 40.

I would expect that melting would continue at an accelerated clip this week but without any significant rain I would bet that we'll get rid of a good amount of snow without any problems.

Unless we get another 3"+ rain storm within the next few weeks I think we may be OK.
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Old 04-14-2008, 11:02 AM   #22
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For the most part I agree with that. No rain is in the forecast for the next several days, which will help keep melting to a trickle for at least the first part of the week as temps stay pretty cool.

I am getting gradually more concerned about Thursday-Friday. What started off as a 60-degree forecast for Thursday is now showing a warming trend with each update, and now looks like upper 60s/near 70 for both days. As I mentioned earlier, the season's first 80-degree day often starts off as a much cooler forecast because we're usually unwilling to commit to such a forecast until the day before. Therefore, I would not be surprised if Thursday and Friday ended up being 75-80 both days with a couple of places reaching low 80s. HOWEVER... I am not committing to that forecast. Only saying it's possible based on the trend I'm starting to see, and what it often means at this time of year. Keep watching the Thurs-Fri forecast to see if it works out that way.

Much of the snow to the south of the lake has now melted so we're in good shape there... at least from floodwaters originating locally. If Thursday-Friday do end up having our first taste of summer (which is not unusual for mid/late April) it would be runoff from the mountains we'd have to deal with, and would be a matter of predicting how far downstream the "bulge" would go before the riverbed was wide/deep enough to swallow it. For that, we would turn to a different breed of scientists, the hydrologists. They've been doing a lot of number-crunching since this flood threat became apparent in late February.
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Old 04-14-2008, 12:23 PM   #23
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http://www.des.state.nh.us/rti_home/...g_stations.asp

Here is the link to the snow pack data that DES collects. Another survey will be done tomorrow (4/15) and should be available by 2PM.
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Old 04-15-2008, 12:25 PM   #24
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Default Good news for the Merrimack basin

As of Tuesday the Merrimack in Manchester had already crested at just below flood stage and is currently almost at action stage or 1 ft below flood.Forecast is for the river to be 1 ft below action stage or 2 ft below flood stage by tomorrow and continue to drop.We've been real fortunate this year with a nice slow melt and low rainfall during the melt.Keeper can speak to this but it looks like this should help with being able to keep Lakeport flows high enough to keep Winni from flooding like last year unless we see very large rainfall amounts in the near future.
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Old 04-16-2008, 09:02 AM   #25
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SS - so glad to hear that, at least for now, you're not in danger of yet another flood. You've had enough of that to last a lifetime!

Keep us posted.
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Old 04-16-2008, 12:15 PM   #26
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Thanks Pepper.The forecast is for the river to keep dropping through friday.If Waldo Peppers was in my location the last few years you would have needed a "float"plane to stay in business.All looks good right now.
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Old 04-27-2008, 11:00 PM   #27
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Default Flood Tuesday?

Latest forecasts are indicating anywhere from 2-4 inches of rain falling between Monday afternoon and Tuesday afternoon. The NWS is considering flood watches for the area which may be issued during their overnight shift tonight.

They are looking at forecasts for the headwaters of the CT, Saco, and Pemi Rivers where most of the snow pack is now gone and river levels are below action stage but could rise quickly if enough rain falls in a short period of time.

This storm is shaping up like a wintertime Nor'easter except there is not enough cold air to create snow because it's April, but if this was 2 months ago we'd be getting a lot. Instead we will be getting a lot of the liquid equivalent.

At the very least, we will have basement flooding as well as flooding of low-lying areas (the usual places.) In addition, we will see flooding of areas near storm drains that have been clogged by debris left behind by the snowbanks this winter. Road crews haven't had more than the last few days to do much spring cleanup, so I suspect there are a lot of storm drains clogged by stuff the snowbanks left behind. And we'll know exactly where they are, come Tuesday, judging by the way the weathermaps look now.

One more concern is the fact that many roads are in various degrees of suffering from what winter did. So, it might not take the rain much effort to further damage or even wash out sections of roads that are already 'hangin' by a thread.'

Also, the lake is very near full. Since I'm not a hydrologist I can't say exactly what situation would push the lake above-full, but it's something you should start watching if you are on the waterfront.

Stay tuned to forecasts and any possible watches that may be issued. A watch is always issued for a general area and means "it's possible so get ready" while a warning is issued for a county and means "It's happening so put your plan into action, if you need to."

This will solve the fire danger problem we had this month.
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Old 04-28-2008, 09:23 AM   #28
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Default Flood Watch through Wednesday

The National Weather Service in Gray Maine has issued a flood watch for its entire forecast area including the lakes region until Wednesday.

The following is quoted from their forecast discussion written this morning (Technical terms have been translated after copying).

ALL MODELS SHOWING
2 TO 3 INCHES OF RAIN OVER A MAJORITY OF THE FORECAST AREA BY 7 AM
TUESDAY. THESE NUMBERS MAY BE UNDER DONE CONSIDERING SLOW MOVEMENT
OF THE SYSTEM AND LONG FETCH OF ATLANTIC MOISTURE FEEDING INTO THE
SYSTEM WITH THE POSSIBILITY OF SOME DEGREE OF TROPICAL MOISTURE
GETTING INTO THE ACT LATE TONIGHT AND TUESDAY. FLOODING WILL
CERTAINLY BE AN ISSUE ON MOST MAIN STEM RIVERS IN THE
FORECAST AREA ALREADY NEAR BANK FULL DUE TO SNOW MELT...SO WILL BE
ISSUING A FLOOD WATCH FOR THE ENTIRE FORECAST AREA WITH THIS
PACKAGE. SEE HYDRO SECTION BELOW FOR DETAILS.

Hydro section...

HIGH LEVEL OF CONFIDENCE THAT FORECAST AREA WILL SEE 1 TO 2 INCHES OF RAIN TODAY THRU TUESDAY WITH 3 TO 4 INCHES POSSIBLE. THIS MUCH RAIN COULD LEAD TO FLOODING ESPECIALLY WITH RIVERS AND STREAMS SWOLLEN FROM RAPID SNOWMELT OF WHAT WAS A VERY DEEP SNOW PACK ACROSS THE FORECAST AREA. THUS A FLOOD WATCH HAS BEEN ISSUED FROM MIDNIGHT TONIGHT THRU EARLY WEDNESDAY MORNING.
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Old 04-28-2008, 11:27 AM   #29
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Default My 2 cents

All the rivers (except for a few way north) are down 2 to 4 feet from their big melt high of last week so there is some capacity there for runoff. The southern part of the state had long been snow free and was very dry so south of the lake there is capacity for the soil to soak up some rainfall.

The Lakeport dam outflow is not unusually high so the operators there seem to be content to let the lake go up a bit more for now.

Bizer's lake level chart is very interesting because of its historic picture. Almost every year the lake starts rising steadily and then sometime between mid April to mid June there is a bump up that I would suspect is associated with either a single very big (6+ inch) rainfall or a rapid sequence of smaller rain events. Over all it is pretty common for the lake to go over "full" for a while in the spring.

The rest of the week is forecast to be dry. My seat of the pants guess is that if we get 2 inches or less not much exciting will happen. If we get 4 inches there will probably be flooding in the areas commonly prone to spring flooding and drying out in a day or two.

Do you think we could train Woolly bear caterpillars to do flood forecasts?
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Old 04-28-2008, 08:22 PM   #30
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Default An inch of rain has fallen

An inch of rain has fallen at Black Cat Weather Station from this storm. Radar indicates several areas of heavy rain (yellow) forming over New York State, Connecticut, and Rhode Island. This activity is moving toward NH and Maine. Moderate rain will continue until the heavy stuff gets here late tonight.

As in wintertime, a secondary low pressure area is expected to develop off the mid-Atlantic coast and create (wet) Nor'easter conditions on Tuesday. The energy associated with this system may be sufficient for thunderstorms to spring up within the greater storm. If these form, they could drop an inch of rain on specific towns in an hour's time. This rain would be in addition to whatever the surrounding area gets from the general rainfall.

The National Weather Service in Gray Maine said in their latest forecast discussion that flood warnings could be issued as early as 11 pm. These would likely be for smaller rivers or streams over-full. On Tuesday any thunderstorms embedded within the greater storm may result in localized flash flooding, when water levels on roads or near homes rise to several inches (or feet) deep within minutes due to an all-out downpour. If this happens, the NWS issues a flash flood warning for the specific area where it's occurring.

Localized flooding may also occur in areas where the recently-melted colossal snowbanks have left heaps of dirt and debris on or near storm drains. Washouts may occur where localized flooding flows across roads already chewed up by the hard winter.

The following is the latest public update (not the forecast discussion) from the NWS.


FLOOD WATCH
NATIONAL WEATHER SERVICE GRAY ME
843 PM EDT MON APR 28 2008

...A HEAVY SOAKING RAIN WILL CONTINUE THROUGH TUESDAY...

.LOW PRESSURE OVER NORTHERN NEW JERSEY THIS EVENING WILL
TRACK NORTHEAST...CROSSING NORTHERN ENGLAND TUESDAY AFTERNOON
AND EVENING. AHEAD OF THE LOW...A DEVELOPING SOUTHEAST FLOW WILL
BRING AMPLE AMOUNTS OF MOISTURE IN FROM THE ATLANTIC...RESULTING
IN LOCALLY HEAVY RAINFALL.

RAIN HAD OVERSPREAD THE ENTIRE REGION BY THE EVENING HOURS...AND
THE RAIN WILL CONTINUE OVERNIGHT INTO TUESDAY. THE RAIN WILL FALL
HEAVILY AT TIMES...ESPECIALLY LATER TONIGHT AND TUESDAY MORNING.
SINCE RIVERS ARE STILL RUNNING HIGH FROM THE RAPID SNOWMELT OVER
THE PAST TEN DAYS...THE EXPECTED 2 TO 4 INCHES OF RAIN MAY RESULT
IN RIVERS RISING TO BANKFUL OR HIGHER LATER TONIGHT THROUGH
WEDNESDAY MORNING.
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Old 04-29-2008, 06:50 AM   #31
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Default

Indeed the streams in my area are running at pretty high levels. More rain today could start making things get ugly.
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Old 04-29-2008, 07:28 AM   #32
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Default Urban & Small Stream Flood Advisory

The National Weather Service issued an urban and small stream flood advisory for much of NH for today. It means the same thing as a river flood warning but on a smaller scale, so the stronger word, 'warning' is not necessary.

There is also a river flood warning in effect for the Saco River near Conway because the river is nearing flood stage this morning.

Lake Winnipesuakee is either at or above full level now. This is indicated by the submersion of Black Cat Shoals in the WeatherCam. The last reported lake level from DES was yesterday morning.

Black Cat Weather Station has received 1.99 inches of rain since 10 a.m. yesterday and more is likely for today. The good news is that the state has gotten into the 'dry slot' of this storm. Radar indicates very heavy rain over our neighboring states of Maine and Vermont, with a moisture feed coming off the Atlantic Ocean. The rain to our east will stay there, while the rain to our west is what we'll have to deal with today.

While the rain to our west is heavy, there isn't much of it, so it won't take more than a few hours to pass. After that, we'll taper to showers and skies should begin to clear later tonight.
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Old 04-29-2008, 01:05 PM   #33
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and to think that Saturday we couldn't burn because it was too dry
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it's tough to make predictions specially about the future
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Old 04-29-2008, 02:30 PM   #34
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Default More rain on the way today

Black Cat Weather Station has received 2.36 inches of rain from the storm so far and more heavy rain is falling. Radar indicates bands of moderate and heavy rain rotating in from the ocean.

This storm is proving itself a wintertime system as advertised. Cold air is feeding into it from the northwest and this has caused a change to snow in Vermont at elevations above 1000 feet. This change may also take place in the mountains and foothills of New Hampshire before the day is out.

Temps here at the lake are 42 and dropping at a rate of 1.5 deg. per hour.

The National Weather Service has issued a freeze warning for parts of New York state for tonight and also frost advisories in southeastern Massachusetts. Tonight we are expected below freezing here as well.

It now appears that the dry weather to follow this storm may only last until the end of the week. A warm front will approach on Friday. If it pushes through here, we'll have a warm and springlike weekend. Models are now hinting that it will stall instead, allowing a continuous moisture feed into this area.
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Old 05-04-2008, 01:29 AM   #35
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Default More rain on the way

Just what you wanted to hear, I know... but there's another inch of rain on the way for today (Sunday.)

The warm front mentioned in my above post from a few days ago has stalled out to the south of here, and has been the cause of all this cloudiness we've had the last several days. This warm front is associated with the same low pressure system (storm) that just dumped record snow on the northern plains and tornadoes to the south and east of there. That storm is weakening as it moves into New York state, but we're back in the wintertime pattern which means the storm will spawn its offspring along the mid-Atlantic coast which will then become the dominant one.

This whole process will mean more rain... just like in February when it meant more snow, except its not that cold anymore.

Look for rain throughout Sunday, heaviest in the late morning and early afternoon. Highest rainfall totals will be to the south, less to the north.

A cold front will clear the whole mess out of here on Monday but will also result in below-normal temps for at least the first half of the week. It looks like we may get a few showers late in the week (maybe) and then next weekend is starting to look like "a typical day in Ireland." Yay.
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Old 05-04-2008, 07:28 AM   #36
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Default Enough water?

It looks like the dam operators at Lakeport have decided we now have "enough" water in the lake because they have started to increase the outflow. Downstream rivers have subsided a bit from earlier so the extra flow shouldn't cause problems. There are showers forecast on and off through the next ten days. It they really are showers not much will change. If we get another stalled soaker the lake level could get interesting.
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Old 05-04-2008, 11:21 AM   #37
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Default A fizzle?

The increased dam outflow is good news. Want some more? Looks like I blew the forecast for today. Since midnight we've had 0.14" rain here. Radar shows "not much" out there. So, unless those dark green and yellow blobs start springing up out of nowhere, today might actually be a mostly rain-free, although damp, day.

Last night New York state was filled with radar echoes of heavy rain, moving into Vermont. And it now appears that just after I went to bed, they miraculously fell apart.

This is one of those times I'm glad to be wrong. Hopefully now the lake level can start to fall.
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Old 05-04-2008, 06:43 PM   #38
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When you think of it on a global scale, you weren't off by much.

I awoke at ~5AM here in N Central MA this morning and it was pouring! This kept up until at least 9AM. We had close to half an inch of rain today.
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Old 05-07-2008, 01:04 PM   #39
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Default Stormy times ahead...

Get out and enjoy the 70+ temps we have today, because the weather pattern is showing signs of "pulling a February" on us after today. By that, I mean one storm after another... not snow as it was in February (this is May, after all) but with the lake still above-full, the last thing we need is heavy rain in the basin.

It is starting to look like we are going to get a chunk of Friday's nor'easter which earlier looked like it was just going to graze us with showers. After a "cloudy & damp" break on Saturday afternoon and Sunday morning, the next storm moves in from Sunday into Monday and the National Weather Service in Gray is already advertising that one as "potent" in their discussion.

In the same discussion, they are hinting at another storm for later next week. If any of these storms start to look like more of a certainty I'll take my own look at the models to make a Winni forecast... in the meantime I'll just leave you with this sort of "Start watching" alert in case it all starts coming together.

NOAA has us circled for heavy rain both Friday and Monday, on their national map of potential hazards (available on the Winnipesaukee WeatherCenter site under "forecast maps.")

As with all the winter storms, the computer models have been doing a lot of flipflopping on their predictions for these storms, so stay tuned if the possibility of heavy rain is a concern to you.
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Old 05-07-2008, 01:13 PM   #40
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Anything you can do to break this pattern of great workdays and lousy weekends is appreciated!

The yardwork list is getting longer and not much can get done in a cold downpour.
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Old 05-07-2008, 01:41 PM   #41
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Ahhhhhhh, if only I could control the weather.... Last winter's snow would've been all fluffy western-style powder and NH would've gotten the 9-foot snowstorm instead of California's mountains.... If I could control the weather, you'd know it, every year between Thanksgiving and Easter, you'd know it!

This spring I gave up on hoping for a long stretch of good yard-work weather and started telling myself, "I spent all this money on a super-duper waterproof Gore-Tex jacket for *what* reason? I might as well get my money's worth from this Gore-Tex." Raking in a light rain, I discovered, has benefits like "no dust" and if you have a fire permit, you can burn 'round the clock as long as it's raining... otherwise you have to wait until after 5 p.m.
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Old 05-07-2008, 07:56 PM   #42
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Quote:
snow would've been all fluffy western-style powder and NH would've gotten the 9-foot snowstorm instead of California's mountains.... If I could control the weather, you'd know it, every year between Thanksgiving and Easter, you'd know it!
When you figure it out, I'll pay for that! Then I would have to retire to fit in all the skiing!
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Old 05-09-2008, 01:15 PM   #43
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Default Dodging the bullet (barely!)

Looks like tonight's storm system is going to keep most (if not all) of its rain out of the lakes region. At 2 p.m. radar indicates heavy rain over the mid-Atlantic states beginning to cover Massachusetts and trying to move northeastward, but in the loop it looks like it's ramming up against a brick wall at the NH border. I would expect showers to make it into southern NH later today and tonight. Best chance of rain drops from this system will be from Laconia to Alton. There's still blue sky showing through a high/mid-level overcast at Black Cat this hour. Temps are not as warm as yesterday but it's still a work-outside day.

High pressure will clear things out later tomorrow into Sunday. The next storm system, a big nor'easter, now looks like it too will be more of a NYC storm than a Boston or Portland storm. That could change, so stay tuned. If it does end up missing us to the south as currently forecast, it would be the second time in 3 days that we dodge a big bullet, given the area's flood potential.

Overall, we have dodged a bigger bullet than we know, the way this spring's meltdown has gone. A record snowpack at the end of winter has resulted in barely any flooding in this area, which is miraculous considering the floods we've had in the last 3 years.

On our side now are the trees. The trees around the lake are now about halfway to full-leaf and they've really sprung out this week, from barely discernible buds to a noticeable green. That means they are now drinking a lot of water. With the trees' growing season now begun, it will take more rain from a storm to create flooding because a lot of it will get consumed by the trees before it has a chance to run off and cause flooding.

I'm not a tree expert, but I'm guessing this high-growth time of year for them is probably helping to draw down the water table near the lake, just enough to help the dam's outflow be more effective in getting the lake level to its normal elevation for this time of year.
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Old 05-13-2008, 04:59 PM   #44
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Default Back to normal

With the lake elevation now back to normal "full lake" (504.32 feet, exactly, as of today) and dry weather for at least the next couple of days (Fire weather watch in effect), I think we can declare the spring 2008 flood potential OVER. Great job, dam operators!

This does NOT mean we can't get a flood... only that the spring melt has come and gone, and the lake is back to normal. If there's a situation that causes flooding this year, we can start a new thread on it, because it won't be part of the spring melt process that we were all concerned about. What a colossal process that was! And to think, it managed to happen without a colossal flood. Miraculous!
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