Snow has arrived and will remain entrenched through the night. Cyclogenisis has begun and 2-4″ per hour snowfall rates will be common inland ( 15 miles inland from the coast.) and 3″ per hour rates at the coast though inefficient accumulation will lead to lesser totals. Thunder will be likely at the peak intensification time ( 10pm-2am)
Snow amounts stay the same.
4:15pm EST Friday 2-24-12
New radar updates filtering in now and the situation is clear. Definite spin with the original low and secondary low forming as well. The low has stalled and so precip will hold off until after dark. Second low will intensify as it moves NE and bring more stable accumulations with dropping temps. Snow will end near dawn Saturday in most areas excluding the mountains where upslope snow showers will continue to crank Saturday
Coast south of Portland- Coating to 1″
Coast north of Portland – Bath excluding Yarmouth, Freeport and Falmouth 1-3″
5 Miles inland to 20 Miles inland including interior Casco Bay- 3-6″
20 miles inland to mountain zones 4-8″
Strong coastal low developing rapidly with cyclogenisis occurring near 40N 70W as the low moves NE.
Updates will continue to flow in as the weather continues to progress.
7:45 pm EST Thursday 2-23-12:
New forecasts coming in now and still trending cooler. This means that the secondary low will develop more quickly and reach a greater intensity before being driven off by approaching high pressure that will be building in for Saturday.
Low will approach the area tonight and snow will start at around 5:30am. Little accumulation before dawn but this thin layer will set the stage for more efficient accumulations with heavy snows later. Heavy snow will come with the 2nd low forming roughly 50 miles NE of Boston. This new low will start out fairly strong and will continue to deepen though cyclogenisis is not expected at this point. The new low will start to pull in sufficient cold air starting around 11:00. Warm air advection (which is warm air interacting with cold air usually overtaking it and produces precipitation) will be halted or significantly slowed by this point due to cool air being wrapped in by this point by the secondary low.
East winds brought on by the secondary low passing south of us will draw in warmer air along the coast and we will see a change to sleet possibly mixing with rain.
Snow amounts: Southern York County: 1-3″
Coast north of Portland to 20 miles inland: 3-5″
Inland and foothills: 4-6″
3:45 pm EST Thursday 2/23/12: Snow will overspread the region Friday Morning and continue throughout the day peaking at around noon. Temps will hover near freezing or a little bit above throughout the day. Temps will sharply rise in the 500 hour when a warm front comes through. This will cause a change to rain up until maybe 5 miles from the immediate coast. This changeover will persist for an hour or 2 and then cooling takes place after dark returning snow for all. Snow will taper off and end at around 2-3am north to south. Clear skies return with blustery conditions saturday.
Friday will feature essentually a very stormy day. Rain at the immediate coast and snow in the mountains with mix in between.
Going in depth a little more… A low will intensify as it moves NE out of the Ohio valley and into New England Friday morning. Snow will overspread the region Thursday night and will stay snow across the entire forecast area untill ~8am. This is where the forecast becomes very tricky. The coast south of Portland will experiance the changeover first with rain overrunning that area and remaining locked in place as warm air pushes north. Meanwhile a secondary low undergoes cyclogenesis over Cape Cod. Depending on how strong this low gets, the warm air could stall or even retreat slightly.
There are 3 dominant senarios for the secondary low development: 1) 2nd low deepens more rapidly and pulls in significant cold air therefore resulting in more significant coastal snows. 2) 2nd low fizzles and gets absorbed by intensifying main low therefore pulling in little to no cold air resulting in minimal coastal snows and hevier upslope snow. 3) 2nd low deepens at a marginal rate resulting in a moderate amount of cold air being pulled in and causing the warm air to be bottled up resulting in a sharp coastal front with a steep temperature difference. The exact placement of this front will likely determine the rain snow line if senerio 3 plays out
Our next storm will be impacting the region Friday with rain at the coast and snow inland. The mountains will pick up a few inches of wet snow. Rain will dominate at the coast. A late weekend storm will pass far out to sea and will not impact the region.
A storm will develop along a cold front and will move NE through the day. Amounts will be light other than far east Washington county where up to 1′ of snow could fall.