Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 100043 AFDGYX Area Forecast Discussion National Weather Service Gray ME 743 PM EST Fri Dec 9 2016 .SYNOPSIS... Cold air from Canada will continue to move into the area tonight and Saturday, with temperatures likely remaining below freezing for the weekend. Saturday night into Sunday morning will be quite cold with some areas falling below 10 degrees. Low pressure moving through the Great Lakes and toward New England on Monday will spread snow into New Hampshire and Maine beginning Sunday night. Expect accumulating snowfall areawide, though there may be a chance to rain near the coast during the day on Monday. Snow will come to an end Monday night as low pressure moves east leaving mountain snow showers in its wake. Seasonably cold weather continues through the middle of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 740 PM...All in all forecast remains on track. HAve kept pops up a little longer for the upslope, through the evening, but overall the SHSN should be on the decline overnight. Also lowered sky cover outside of the mountains overnight, and tweak temps just a bit based on current obs. The gusty winds are slowly diminishing, although they will probably persist through the evening before they settle in around 10 mph overnight. Low will range from the single digits in the mountains to the mid-upper teens in srn NH and on the ME coast. Previously...Cold air continues to filter into the region in the wake of the cold frontal passage. Snow showers have continued through the day as the mountain flow remains unblocked. Overnight the winds will decrease as the pressure gradient lessens. Snow showers will come to an end around nightfall as the winds decrease. Overnight lows will drop into the single digits north and teens south with the light winds preventing further radiative cooling. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Saturday high pressure will move over the region with cold air aloft moving in. Skies will be mostly clear in all but the northern mountains. Overnight temperatures will drop to the lowest seen this season. Temperatures will reach the low teens all the way to the coast. Have dropped temperatures below guidance especially in the valley bottoms that radiate well such as SFM HIE and BML. In the mountains the residual moisture may lead to some patchy freezing fog in the valleys which will help to keep temperatures above zero through the region. && .LONG TERM /SUNDAY THROUGH FRIDAY/... A low amplitude shortwave trough will track eastward through the Great Lakes and into New England on Monday while the broader upper low (and core of the colder air) slips southeast out of the Hudson Bay region of central Canada and into northern New England later this week. This will spell a below normal temperature forecast through the period with a chance of wintry weather on Monday. The details: High pressure moves east across the area on Sunday with light winds and cold temperatures continuing. Air mass moderation may lead to high temperatures a few degrees warmer than Saturday, but still below freezing. Temperatures drop into the teens again Sunday night for much of the area, while increasing clouds coming in from the southwest will hold temperatures in the 20s there. Surface low pressure tracking through the central Great Lakes Sunday night will begin to occlude as the leading edge of its influence reaches the Atlantic Coast. Secondary low pressure is expected to form early on Monday generally near New York City and tracking northeast toward Cape Cod and southern New England. This track favors cold air remaining in place over northern New England and precipitation remaining as snow for most areas. A track closer to the coast will allow for the coastal front to push further inland along the Maine and New Hampshire coastline on Monday. The American models tend to favor a track closer to the coast with a transition to rain along the coast and even fairly far inland. Meanwhile the European model tracks the low offshore of Cape Cod keeping precipitation as all snow even to the coast. Current forecast thinking favors a blend of the two solutions, with a greater weight toward the snowfall forecast over the transition to rain. An easterly low level flow in advance of this system should maintain fairly deep cold air damming over interior western Maine and eastern New Hampshire, which should prevent the rain/snow line from moving much further inland than the Route 1 corridor in opposition to the NAM/GFS solutions. Expect the snow to begin from southwest to northeast Sunday night into Monday morning. By daybreak the snow should be spreading across the entire region, with a few inches of accumulation already on the ground over much of New Hampshire. The heaviest snowfall rates are likely to occur in the morning hours on Monday as the low moves by offshore. Snow ends from west to east Monday evening. It is possible that there could be some light drizzle or freezing drizzle as the system passes by to the east but low level moisture remains in place below a dry slot aloft. Any impacts from this should be minor considering the several inches of snowfall expected beforehand. Total snowfall accumulations are likely to be in the 4 to 7 inch range for most locations, though there could be less along the coast if the coastal front is able to move in and change things to rain before coming to an end. Low pressure moves east Monday night with lingering snow showers possible in the mountains and a westerly flow in the wake of the low. Highs on Tuesday should reach the low to mid 30s, but remain in the 20s in the mountains. Another surge of colder air arrives on Wednesday when a northern stream trough tracks through Quebec. Models are not in good agreement on what to do within the storm track to the south of the larger Canadian upper low. The GFS would like to develop a coastal low that brings more snow to our area Wednesday into Wednesday night, but the ECMWF does not generate a storm until it is further east out into the Atlantic. At this point will try to split the difference for the forecast and include a chance of snow, but the ECMWF solution seems a bit more realistic given the lack of a sharp trough to drive cyclogenesis. Either way, temperatures should be cold even for this time of year as the core of the cold air drops into our area late next week. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... Short Term... gusty winds will continue for the next few hours before decreasing overnight. HIE will continue to see MVFR SHSN overnight. VFR conditions will prevail for Saturday with a chance of IFR FZFG for HIE late Saturday night. Long Term...VFR conditions expected Sunday, but should see deteriorating conditions Sunday night into Monday morning with snow moving in from the southwest. Heaviest snow will be Monday morning, with a change to rain possible along the immediate coastline during the day Monday. Should see widespread IFR to LIFR conditions during the heaviest snowfall, even occasionally going to 1/4SM in heavy snow. Conditions improve Monday evening into Monday night except for the mountains where lower ceilings could remain an additional 24 hours. && .MARINE... Short Term...740 pm update...Lowered the gale to SCA on the outer waters and dropped the SCA in the bays. Winds are gusting to around 30 kts outside of the bays, and this will persist through most of Saturday. Long Term...Coastal low tracking through the Gulf of Maine on Monday could produce advisory level wind speeds as it moves through. There is a low chance that winds could reach gale force for a time ahead of the low. Winds become westerly to northwesterly behind the low Monday night and could remain near advisory levels through Tuesday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 4 PM EST Saturday for ANZ150-152- 154. && $$ NEAR TERM...Cempa/Curtis SHORT TERM...Curtis LONG TERM...Kimble AVIATION...Curtis/Kimble MARINE...Curtis/Kimble

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