Something's brewing

[Rose]

Keep an eye out for a storm late Thursday into early Friday. Two of the American models are developing a strong but fast moving storm that gives us primarily snow, while one of the Canadian models has it too far south to affect the Lakes Region much. The longer range American model is run in "ensembles" which means they tweak some of the inputs to see how the forecast changes. All 12 of the model ensembles have some portion of a storm either over us or approaching us as of 7:00 pm Thursday night.

[Resident 2B]

I agree with what Rose has posted.

There are several mini-events of snow/ice/rain, the first of which we got last night and today, associated with a front that is relatively stationary over us extending back to the southwestern US. The start of the weekend looks like we will have the last in this series of weather systems. The models show activity, but they are showing different impacts for the lakes region, five days out.

The GFS has a poor record in the five to six day range, so that model for now may be wrong with a weak system passing south.

The model with the biggest punch is the fairly accurate Euporean Model. It looks somewhat "overblown" to me, but if it is correct, we get one heck of a storm late this week or early in the weekend.

Other models are somewhere in between as are the ensembles.

With all the activity, it will be an interesting and slippery week, and it could end with a big white bang this weekend. Looks like winter starts in the traditional manner this year, unlike what we have had the past few years.

As usual, time will tell!

R2B

[Blue Thunder]

I know the GFS usually stinks more than 5 days out, but it has had a huge coastal storm progged for the 17th for 2 weeks. Now I know what you're going to say...and for the most part I agree, but if it pans out with the NAO going negative, we "could" have a bomb on our hands. All we have to do is wait for the TV guys to start the hype.
http://www.nco.ncep.noaa.gov/pmb/nwp...s_pcp_150l.gif
Move your cursor on it and then click to enlarge it and look at the East Coast.

Blue Thunder

[chipj29]

The first storm (tonight) will be very light, and will be liquid for those of us south of the lake. The second storm looks to be a bit surpressed, but should be white. Look for the jackpot to be in Mass. However the third storm, coming on Sunday, looks to be a good one for our area. Should be a true nor'easeter, with interior areas getting the best snow. Keep your fingers crossed!

[Resident 2B]

It is looking more like if we get a big "white" storm, it will be later in the weekend.

Since the Pats are at home and there is some history with Pats home games in snowstorms in December, I am starting to buy in to the likelihood of this actually materializing.

It looks like all the pieces are coming together. There should be very cold air over us and to the north with very warm and moist air to the south. A high pressure area should be holding to our northeast. The negatively tilted trough is in place now and looks to hold. The only pieces left are timing of low pressure development and exact storm track and that will play out as time goes on.

Looks like a fun week ahead!

Enjoy!!

R2B

[Skip]

You guys (and gals) have got to stop teasing me!

This will be my first season as a volunteer groomer operator for my snowmobile club, so I'm like a kid at Christmas Eve just waiting for the heavy snow to fly!!!

[Weirs guy]

I want to rescind my vote for the weather thread Don, I liked it better when I didn't know.....

[Resident 2B]

Skip and Weirs Guy,

This is still a 50/50 storm, maybe 60/40 at best. It was a 30/70 event yesterday. Do not take these forecasts to the bank! Models are not that good.

R2B

[trfour]

They talked about it on the national news tonight, said it could be a monster snow storm by late Sunday into the first of the week.

Think Snow!

[Weirs guy]

Originally Posted by Resident 2B

Models are not that good.

Raises a great, actual on topic question for me. About how far out is the average forecast accurate for?

[CanisLupusArctos]

Accuracy depends on the computer model and the situation, and location also plays a role.

On average I would say we're up to pretty decent 4-day forecasts for average weather. If a storm gets into the picture at 4 days out (or more) consider it just 'something to monitor' rather than a set-in-stone forecast. At 3-4 days the models can usually say with certainty that a storm will form in a general location, reach a certain strenth, and what general track it will take. Anything more detailed can't really be predicted until 24 hours in advance.

Accuracy depends on which model. Many forecasters call the Nested Grid Model (NGM) The "No Good Model." Some are better at long-range forecasting while others are at their best for tomorrow's forecast. Often a couple models will do better than others for no apparent reason, so forecasters will tend to favor them until the winning streak finally ends.

Accuracy also depends on location. The models take local and global weather patterns into account. In most of the world, weather comes from a max of 2 directions, making it easy to predict.

New England's weather normally comes from three directions (the only place in the world where that happens) and sometimes four. If that weren't enough, our extremely varied topography throws those models off all the time. Our highest point is 6,288-foot Mount Washington, just 65 miles from the oceanfront at Portland. That's quite a vertical variation over a very short distance.

At any given time New England's weather can be influenced by A) The Ocean B) The Arctic C) The Gulf of Mexico/Tropics and D) The continental US.

Models often don't know what to do with this. The same model might make a great 5-day forecast for Colorado but have no clue what to do with New England's 24-hour weather.

Think of the models as being similar to the scenery in an extremely realistic flight simulator game. They have landforms and they interact with the atmosphere. They have a resolution (sharpness) just like your game graphics. Their resolution is WAYYYYYY better than it was in the 1980s, but they still don't show the White Mountains as high as they are in real life.

As the computer models' resolution improves, so will the accuracy of forecasts. It wasn't too long ago that most of them showed Boston blobbed together with southern NH and Cape Cod. In a place like Kansas, having a lack of detail over such a small area isn't a big problem, but in New England the weather varies greatly in that small area, and the models couldn't show it until just recently.

[ITD]

Originally Posted by Resident 2B

ITD,

I do not think you heard that here.

The models we are talking about go out 48 to 384 hours.

They are unable to predict global warming/cooling trends. They are designed for weather forecasting in the near term.

R2B

I meant they as in the people, not the models, anyway I deleted the post. Sorry for pulling a Less.

[Resident 2B]

Just deleted my response.

R2B

[Lakegeezer]

The meteogram (through 600Z Sunday) from Manchester NH http://wwwt.emc.ncep.noaa.gov/mmb/na....meteogram.gif seems to be conflicting with the other forecasts calling for a chance of snow this Saturday night. It shows the pressure rising, the temperature falling and the winds from the northwest. Will the brew be late or fizzle?

What "storm watch" web sites do you find useful? The 3 hour pressure change graphic http://weather.unisys.com/surface/sfc_con_3pres.html is one of my favorites to watch, just before a storm hits. It shows where the storm is forming and reforming, validating or exposing the current forecast.

[Sunrise Point]

New England's weather normally comes from three directions (the only place in the world where that happens) and sometimes four. If that weren't enough, our extremely varied topography throws those models off all the time. Our highest point is 6,288-foot Mount Washington, just 65 miles from the oceanfront at Portland. That's quite a vertical variation over a very short distance.

Thank you C..L..A.. That's the most concise and the best description of the variable New England weather that I have seen yet. I am looking forward to this weekend in NH. In weather like what is forecast for this weekend, if I had a choice between a centrally heated (but dependent on electricity) house in MA or a camp in NH with a propane cook stove and a wood stove for heat, I would choose NH anytime. Now if I can just chop through the ice for water.....

[Skip]

Count me in the "weather nut" column too, but I have nowhere near the expertise as some of you guys & gals obviously do!

But my favorite Winni prognosticator? Why Rose, of course....whenever she can tear herself away from her busy schedule & eyeball a few charts and graphs for us.

But my right knee is starting to ache....and my snowmobile is creaking in its hinges out in the garage tonight. Methinks that we are in for a white weekend that we may remember for a time or two to come!

We shall see.....

[Rose]

Originally Posted by Lakegeezer

What "storm watch" web sites do you find useful?

I like the surface plots at Penn States e-wall site. You can loop either 8 or 24 hours worth of plots...here's the link to the 8-hour loop.

http://www.meteo.psu.edu/~gadomski/SFCNE/sfcloop.html

The only problem is it's tiny on my laptop.

[GWC...]

Rose seems to have provide good guidance for Thursday - Friday event...

*** GROWING CONFIDENCE ON A PERIOD OF HEAVY SNOW THU AFTERNOON AND
EVENING ***

FARTHER NORTH WHERE COLUMN IS COMPLETELY SUBFREEZING...CONFIDENCE IS
HIGH FOR A SWATH OF 5 TO 10 INCHES ACROSS INTERIOR CT-NORTHERN RI
/INCLUDING PVD/ AND ALONG AND SOUTH OF I-90 IN MA...INCLUDING THE
GREATER BOSTON AREA. EXPECTING A FLUFFY/DRY SNOW HERE WITH SNOW
RATIOS OF 12-1 OR 15-1. GIVEN PTYPE WILL BE ALL SNOW...WE WILL HOIST
A HEAVY SNOW WARNING FOR THIS AREA.

NORTH OF THIS AREA...SPECIFICALLY NORTH OF THE MA PIKE INTO SOUTHERN
NH...BOTH MODELS GENERATING 0.35-0.45 QPF. IN ADDITION...SNOW GROWTH
IS IDEAL ACROSS THIS AREA. GIVEN COLUMN IS VERY COLD SNOW RATIOS WILL
LIKELY BE 15-1 AND POSSIBLY 20-1. THEREFORE...4-7 INCHES IS POSSIBLE
ACROSS THIS AREA. HENCE...WILL POST A WINTER STORM WATCH FOR THIS
AREA /CONFIDENCE NOT HIGH ENOUGH FOR WARNING/.

HEAVY SNOW WILL TRANSITION TO LIGHT SNOW 6-8 PM WEST AND 7-9 PM
EAST...WITH ONLY FLURRIES THEREAFTER.

[Lakegeezer]

Originally Posted by Rose

I like the surface plots at Penn States e-wall site. You can loop either 8 or 24 hours worth of plots...here's the link to the 8-hour loop.

Thanks Rose! Very nice site.

[Resident 2B]

Originally Posted by Lakegeezer

What "storm watch" web sites do you find useful?

I use the AccuWeather Pro site. They have numerous models that you can loop. There are 50+ GFS attributes that you can isolate and loop. It also has a fast response since it is a commercial site.

The only down side is that there is an annual fee, but when divided by 365, the cost per day is low.

I also use PSU sites since I believe they are the best when it comes to everything weather related, including education.


R2B

[Resident 2B]

For an event now only three days out, the models are quite divided on storm track. GFS Operational seems to be the model in the middle and that has the deep low center inside the 60/40 beancmark passing close to Cape Cod. The GFS ensembles are more to the east and the UKMET and the ECMWF are more inland. The NAM has it well south and out-to-sea.

So what does this mean?

All the models except for the NAM see a big storm with a good wind field for Saturday evening through Sunday in the New England area. So we get a storm. The open question is how much and p-type for specific locations. I am favoring the GFS Operational which gives the Lakes region a Y2 storm on the Yuki scale (about 14"). Of course this can change and the amount in Alton may be a bit different than the amount in Center Harbor, but for now, that is what I am thinking.

If the UKMET and ECMWF are correct, the snow amounts would be less and there could be ice, but I think the bank of cold air in place will not allow the track they are showing to materialize. (See CLA's excellent discussion in this thread about the local complexities for some insight to local affects.) If the NAM is correct then every weather person in the area looks real dumb with a dusting at best. I do not think the NAM has it right.

Time will tell!

R2B

[CanisLupusArctos]

One more local effect to add to the list: Last winter I began thinking that Lake Winnipesaukee acts as a runway for warmer ocean air when there's a major coastal storm (lots of wind). In the major windy storms of last February and March, I found that the snow was changing to sleet and freezing rain here in Center Harbor, even while places like Gilford and Laconia were still having plain snow. The temperatures on the island were also warming higher than those away from the lake.

This led me to guess that when the storm's wind is very strong from the east, the lake's NW-SE orientation (with mountains on both sides) was helping to funnel maritime air farther inland than it was otherwise reaching.

The effect shut down when the storm moved farther north, giving us more of a NE wind rather than East or SE... and any mix would change back to snow.

Something to consider for this weekend's storm will be evaporative cooling in the dry arctic air now in place, should warm air try to intrude. That happened a couple times last winter when arctic air was in place but warm air was forecast to change the snow to mix. The mix never happened, because the dewpoints in the arctic air were so low that the first couple hours of precip evaporated before hitting the ground, cooling the air the same way your skin gets cold when water (or rubbing alcohol) evaporates off it. Gradually the dewpoint rose to a point where the snow could finally reach the ground, but by the time that happened, the air had cooled 5 or 6 degrees -- just enough to keep the snow from mixing with rain/ice.

[fatlazyless]

It's just started snowing pretty good here In Waterville Valley and the mercury thermometer, located at 1540' altitude says 10 degrees. ...cheers to winter!!

[SIKSUKR]

2.5 inches in about an hour here in Manchester.Snowing to beat the band!!!

[CanisLupusArctos]

Thursday's snowfall at Black Cat was 3.1 inches and melted down to 0.21". At midnight it's still spitting with a light snow shower but the accumulation is pretty much done.

CLA

[chipj29]

Got right around 6" in the capital region. All eyes on the Sunday storm.

[CanisLupusArctos]

Another half-inch for early Friday morning brings the event total to 3.6 inches at Black Cat. Winter storm watch now in effect for the lakes region for Sat PM-Sunday. More details on the National Weather Service page or from the Winni WeatherCenter page. The new storm promises some VERY much needed rain for the drought in the south, before it makes its way up the coast.

Models are squabbling with each other 'just a bit,' driving us crazy and this is evident in the differing TV forecasts. Some are saying all snow, others going for more sleet/freezing rain, depending which models they're betting on. However all agree that the Patriots game on Sunday promises to be a good one!

[GWC...]

Originally Posted by Weirs guy

I want to rescind my vote for the weather thread Don, I liked it better when I didn't know.....

Here's a little amusement from the past for the impending nor'easter...

[Resident 2B]

Big storm coming, but the question remains - what type of precipitation will fall at specific locations?

As in now stands, the NWS has a Winter Storm Warning for the northeast side of the lake and a Winter Storm Watch for the southwest side of the lake. This is due to the NWS forecasts being issued by counties. However, it shows that the lakes region is right on the line of all snow/mixed precipitation. (Edit: At 3:22 PM, the NWS issued a Winter Storm Warning for the entire Lakes Region.)

Models are showing a powerful storm on the New England coast tomorrow. This would give a snow to rain event in southern New England, and a heavy all-snow event in the northern mountains. Since the lakes region is in between these two areas, the forecast for the lakes region is a tough one.

I had projected a Y2 storm, and it will be that or more where it is all snow. I think that we will see a period of sleet in the region that will hold down and pack down the snow at the height of the storm late tomorrow afternoon. How much sleet is a big question. With backside snow into Monday, we still could approach Y2. It looks like the freezing rain will stay south of Alton.

Temps will drop bigtime after the storm, so if the snow gets wet, there will be little time to remove it before it hardens.

Go Pats! Should be a wet game there with a lot of wind.

R2B

[CanisLupusArctos]

With warm air projected to intrude on the area during the snowstorm, it's likely that anywhere near the edge of the 'all snow' zone (and in the mix/rain zone) will get several hours of sticky wet snow. Since high winds are also a part of this system, this could produce some damage from snow-laden objects (including trees) falling.

This will not be much of an issue if the storm keeps us well within its 'all snow' zone where colder temps should allow for a more powdery snowfall. There, blowing snow will be a visibility issue, but there shouldn't be much damage.

Also, as R2B said, get rid of wet snow and/or standing water quickly because as soon as this thing passes it's going to pull down some really frigid air (some of us will get below zero for the first time this season.) This will cause everything to freeze and become impossible to remove without a flamethrower.

Re-freezing won't be an issue on the colder side of the storm where the powdery snow falls.