Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 090328 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1028 PM EST Thu Dec 8 2016 .SYNOPSIS... Another cold front will cross the region overnight. Mountain snow showers will continue through Friday...with several inches of snow possible north of the notches. The coldest air of the season will move in behind the front...with highs struggling to break freezing even at the coast. High pressure will build in for the weekend continuing cold temperatures. A low will approach the region on Monday with snow spreading across the region and rain mixing in along the coast through Tuesday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 1025 PM...Just a few minor tweaks based on current obs and latest mesoscale models. Secondary cold front still on track to cross the CWA in the 06-12Z range, with upslope snows increasing in intensity in the mountains between and 06-08Z. 740 PM...First cold front now exiting the CWA moving offshore off coastal ME attm. Secondary cold front will cross the region after midnight, and will usher in the colder air. In between there is a little bit of a lull in the SHSN in the mountains, although a few scattered showers and flurries are possible this evening. The better accumulating snow here will begin closer to midnight as the the front moves through and the cold upslope flow kicks in. Overnight low will drop off some this evening, but will wait for the push of cold air, and will range from the low 20s in the north to the upper 20s in srn NH and on the coast. Previously...The first cold front is crossing the mtns at this time...forcing a broken band of snow showers thru the forecast area. Based on area webcams and a small handful of automated observations...visibility has dropped to 1/4 mile at times in these squalls. Temps are also falling below freezing behind the front...especially in the mtns and foothills. So some refreezing of minor snow accumulations will likely occur on roadways. I have issued a couple SPSs to handle this threat into the early evening. After the passage of the front...temps will gradually decrease overnight in a well mixed environment. Upslope snow showers will tend to stick closer to the high Froude numbers go back towards critical after the initial surge of CAA. Then the secondary Arctic front approaches the forecast area around midnight. Once again deeper mixing will allow some snow showers to cross the ridge line and track towards the coast. Snow squall parameters do appear favorable for some of these to also be heavy at times. The focus of the heaviest precip however will remain closer to the highest terrain. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... Cold NW flow will continue on Fri. Closed mid and upper level lows will remain over the Canadian Maritimes...with strongly cyclonic flow directed over the high terrain. With a lingering pool of low level moisture upstream in Canada...upslope snow showers should be favorable for moderate accumulations over parts of Nrn NH and adjacent Wrn ME. It is not out of the question that a winter wx advisory may be needed for a few zones. Farther S...high temps will struggle towards freezing with strong CAA thru the day. Wind gusts will top out around 25 to 30 kts at times...making it feel even colder. CAA continues into the mixing will limit the overall cooling off of temps. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... A relatively zonal flow will persist through the start of next week...with a series of weak waves moving through. By Tuesday a long wave trough develops over Hudson bay and cold air shifts southward into the central CONUS. This will allow for a storm system to move up the ohio valley and into Northern New England. The weekend begins with cold high pressure building into the region. Mountain Snow showers will come to an end of Saturday with clearing skies. Winds will decrease through the region as the pressure gradient decreases. Overnight temperatures will drop to near zero through the mountains... with isolated valleys below zero. A few clouds remaining in upslope regions would be enough to prevent widespread below zero temperatures. On Sunday clouds will start to move in from the west in advance of a developing system moving up the ohio river valley for Monday. The trend over the past few days has been to push back the timing of the storm... with precipitation not moving into our southwestern areas until very early Monday morning. Expect precipitation to begin as snow region wide and spread across the region through the day on Monday. By Monday night the possibilities expand with the changing storm track. GFS tracks further inland which has the effect of allowing warm air aloft to infiltrate through southern maine. With the high pressure for Saturday and Sunday the cold temperatures are likely to remain dammed at the surface, so warm air aloft would put a period of mixed precipitation into southern Maine coastal plain. While a mixed scenario is one possibility, it is not the only one. Increasing strength of cold air aloft could also drive the storm track slightly further south keeping any above freezing temperatures off shore in teh Gulf of Maine. At this point have leaned towards a colder solution, in part because of the strength of existing cold air mass. The track of the storm will also have an impact on the winds, with a south track resulting in a more classic nor`easter type set up with gusts too around 30along the coast. A inland and warmer scenario keeps the center of the storm over us and results in lower wind speeds. Have hedged to the stronger winds in keeping with the colder solution. The active pattern continues through next week with another chance for precipitation on Wednesday. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... Short Term...First cold front is crossing the mtns at this hour with a band of snow showers along it. Very brief IFR or lower conditions are possible with this front...mostly likely to hold together thru AUG...possibly RKD. NW flow develops behind the front...keeping areas downwind of the mtns VFR tonight. HIE will remain MVFR in upslope clouds...and occasional MVFR CIGs may work into LEB overnight. HIE may also see rounds of SHSN that drop VSBYs to IFR or lower at times...especially with Arctic frontal passage around midnight tonight. Strong NW flow continues Fri...with surface gusts around 25 kts. Upslope SHSN continue at HIE thru the day. Long Term... Sunday night MVFR clouds moving in west to east. Expect IFR snow to develop late monday. Tuesday may see a period of mixed precip along the coast. && .MARINE... Short Term...I have upgraded the outer waters to gale warning for Fri...and made the bays SCAs beginning this afternoon. First cold front will cross the waters this evening...with winds increasing to SCA thresholds. The secondary Arctic front crosses the area tonight. Gale force wind gusts will begin behind this front. Strongest wind gusts will linger into Fri evening before gradually diminishing. Long Term... Storm developing Monday into Tuesday will result in wind and waves increasing to near Gale. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 11 PM EST Friday for ANZ151-153. Gale Warning from 10 AM to 11 PM EST Friday for ANZ150-152-154. && $$ SYNOPSIS...Curtis NEAR TERM...Cempa/Legro SHORT TERM...Legro LONG TERM...Curtis/Legro AVIATION...Curtis/Legro MARINE...Curtis/Legro is the U.S. government's official web portal to all federal, state and local government web resources and services.