Winnipesaukee Forum - View Single Post - Saturday, March 8 and a "block" for late March

Resident 2B · 03-06-2008, 10:14 AM

The storm for Friday night into early Sunday morning is looking like a mostly rain event, with 2 to 3 inches of QPF. It is looking like 90% of it will be rain in the lakes region. It could start as sleet or ice but if it does, it will change to rain quickly. It could also end with a bit of sleet or ice, but that would be minor. This wet forecast is very bad news for roof loading and for flood potential.

As far as roof loading is concerned, an inch of rain that is fully absorbed by snow already on a roof or deck adds 5.2 Pounds per square foot. Therefore, if you have a 20' x 30' surface and we get two inches of rain, and it all gets absorbed, you are adding over 6,000 pounds to the total load on the surface. Considering the surface already is carrying a huge load from what is already there, this additional load could push the surface past the yield point. It is the fluffy stuff on the upper levels of the snow that will absorb the water, The heavy stuff at the bottom will not absorb much more water becauser it is already saturated. If you can get the fluffy snow off the roof or deck, you are doing a lot to help your situation.

As far as the weather models, the GFS has been more accurate than usual the last 7 to 10 days. However, it is almost always inconsistant run to run. The UKMET and the European have been much more accurate this winter and in most past winters.

There is still some question regarding the track of the approaching storm, and there seems to be a significant disconnect between current Forecast Discussions from Gray, Me and Taunton, Ma. I think Taunton has it right with a coastal system and Gray has it incorrect with a system going to our west. However, wherever the system goes, it is looking like rain for us. The only question remaining is wind direction, NE if Taunton is right and SE if Gray is correct.

This forecast is not good news. I hope that I am wrong!

R2B

03-06-2008, 10:14 AM	#8
Resident 2B Senior Member Join Date: Apr 2004 Location: North Shore, MA Posts: 1,352 Thanks: 987 Thanked 310 Times in 161 Posts	Getting Ugly! The storm for Friday night into early Sunday morning is looking like a mostly rain event, with 2 to 3 inches of QPF. It is looking like 90% of it will be rain in the lakes region. It could start as sleet or ice but if it does, it will change to rain quickly. It could also end with a bit of sleet or ice, but that would be minor. This wet forecast is very bad news for roof loading and for flood potential. As far as roof loading is concerned, an inch of rain that is fully absorbed by snow already on a roof or deck adds 5.2 Pounds per square foot. Therefore, if you have a 20' x 30' surface and we get two inches of rain, and it all gets absorbed, you are adding over 6,000 pounds to the total load on the surface. Considering the surface already is carrying a huge load from what is already there, this additional load could push the surface past the yield point. It is the fluffy stuff on the upper levels of the snow that will absorb the water, The heavy stuff at the bottom will not absorb much more water becauser it is already saturated. If you can get the fluffy snow off the roof or deck, you are doing a lot to help your situation. As far as the weather models, the GFS has been more accurate than usual the last 7 to 10 days. However, it is almost always inconsistant run to run. The UKMET and the European have been much more accurate this winter and in most past winters. There is still some question regarding the track of the approaching storm, and there seems to be a significant disconnect between current Forecast Discussions from Gray, Me and Taunton, Ma. I think Taunton has it right with a coastal system and Gray has it incorrect with a system going to our west. However, wherever the system goes, it is looking like rain for us. The only question remaining is wind direction, NE if Taunton is right and SE if Gray is correct. This forecast is not good news. I hope that I am wrong! R2B Last edited by Resident 2B; 03-06-2008 at 11:53 AM.