Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 080012 AFDGYX Area Forecast Discussion National Weather Service Gray ME 712 PM EST Wed Dec 7 2016 .SYNOPSIS... The region will sit between two systems tonight...with skies remaining mostly cloudy. A flurry or two is not out of the question...but for the most part it will by dry. The first in a series of cold fronts will cross the area early Thursday. Mountain snow showers will increase in coverage...and cold...gusty winds develop through the day. A second and stronger cold front will cross the area Thursday night. More widespread snow showers and the first real cold shot of the season set in overnight. Gusty northwest winds and mountain snow showers will continue on Friday behind the departing cold front. Cold high pressure will build in for the weekend before the next storm system approaches late Sunday night and into Monday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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710 PM...For the most part, precip has ended across the CWA fro tonight. the only exception will be weak upslope flurries in the mountains this evening, and these will likely shut down by around midnight or so as drier air works in. Otherwise, just a few minor tweaks to T/Td/Wind based on current conds. Lows could be tricky and variable with patchy clearing and light winds at times, but overall should be mostly cloudy in many areas with lows mostly in the mid to upper 20s. some patchy fog may develop in sheltered areas that exhibit more clear skies. Previously...Wly flow is beginning to increase aloft and will slowly begin mixing down tonight to help lift the low level clouds. Mainly followed the NARRE-TL timing for any lifting or scattering out. However...fairly abundant low level moisture means we probably will not fully clear out tonight. I also cannot rule out a flurry or two tonight...mainly in the mtns. As a result of the clouds low temps are on the more mild side for this time of year.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... The first in a series of cold fronts is set to cross the forecast area Thu. Along the leading edge a band of snow showers should develop...and may survive the downsloping to reach the coastal areas. Downslope warming however may help change those over to rain showers during the day. The NW upslope zones on the other hand will see a wintry day...with continuous snow showers. With Froude numbers forecast to be near critical...snow will likely fall closer to the high terrain. The upper trof...reinforcing cold front...and the real cold air arrives after 03z Fri. Another round of snow showers will develop on the leading edge of this Arctic air. And this time around conditions look favorable for snow squalls. Given that daytime temps will have been around normal and above freezing for many areas...this could create a refreeze problem for any snow that falls even if it is light. This is in addition to briefly reduced visibility. Again model forecasts these snow showers could survive the trip over the mtns and work downstream to the coast. Back NW of the mtns...continued transport of low level moisture into the terrain from the NW will favor continued upslope snow showers. With closed mid level low centered to our NE and even H5 forecast to remain closed to the NNE...trajectories will be favorable for more than a light upslope snowfall event. Given the snow growth zone will extend below ridgeline and low level lift will exist in this region...snow to liquid ratios could also be favorable for higher snowfall totals. For now the highest elevations of the Whites and parts of Nrn Coos could see 4 to 8 inches of new snow as it continues into Fri. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... High impact Weather: Widespread snow Sunday night/Monday Overview: A long range trough moves into the eastern CONUS for the weekend bringing cold air with it. At the end of the weekend a low moves out of the great lakes and up the Ohio river valley with widespread precipitation moving into the area for the start of next week. Towards the middle of next week colder air may move in however significant spread in the timing and strength amongst the various guidance. Friday will start off with west to northwesterly flow with a strong pressure gradient as a low departs to the maritimes. Clouds and showers will linger in the mountains through the day. Froude number guidance ranges from 1-2 indicating the potential for flow over the mountains to generate both upslope showers and downslope wind gusts. Airmass with dry out relatively quickly with only around 1-3" expected across the higher terrain. Expect winds to remain strong through the day with gusts to 25-30mph range across the area as the atmosphere becomes well mixed. Friday night winds will decrease overnight although continued cloud cover and a weakening pressure gradient will keep the low temperatures from dropping very far despite -16C temps at 850mb. Saturday the cold air will crest over the region as high pressure moves in at the surface. Only the mountains will see cloud cover with the rest of the area remaining mostly sunny. Overnight Saturday night will see the lowest temperatures bottoming out near zero in the north. A storm system will develop over the lower Ohio river valley on Sunday. This low will ride up the edge of the upper level trough spreading snow and rain across the region late Sunday night into Monday morning. With the instigator of this storm still over the Pacific ocean, there remains quite a bit of variation in the timing with precipitation onset ranging from Sunday afternoon to late Monday morning. Due to the cold weekend the surface temperatures are likely to remain below freezing for all but the immediate coastline, with cold air damming a possibility. Warm air pushing northwards ahead of the warm front could reach far enough north to see some mixing along the coastal plain, however the variation is 850mb temps by Monday night ranges from -10C to +5C amongst the various deterministic models. Due to the wide variability have stuck to a blend for temperatures, with a slight nudge downwards in the interior toward the potential for cold air damming. Have kept ptype to Snow or rain and will hold off on any mixing until closer in. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Short Term...IFR CIGs will continue to slowly lift this evening. MVFR conditions linger thru the 00-03z period before starting to scatter out. Cold frontal passage and onset of NW flow will allow downsloping to lift CIGs to VFR Thu...except for HIE which will likely see widespread MVFR. I cannot rule out a passing -SHSN at all terminals...but upslope SHSN will be most prevalent and likely to be IFR or lower VSBYs at HIE thru Thu night. Thu afternoon may also see a few surface gusts to 20 kts at all terminals. Long Term... Friday will see MVFR in SHSN for HIE winds will pick up with gusts to 25kts at all terminals through the day on Elsewhere VFR remains through the weekend. A storm system will bring IFR SN developing from west to east late Sunday night and into Monday && .MARINE... Short Term...Surface ridging noses over the waters tonight with light winds and seas below 5 ft. The first cold front crosses the area Thu...with increasing NW flow and building seas. SCA conditions will likely develop ahead of the onset of possible gales. At this time gusts over 25 kts will be most like after mid Thu afternoon thru the overnight. Long Term... Cold air advection over the waters with a strong pressure gradient will result in gusty northwesterly winds. A Gale Watch has been issued as gusts are expected to reach at least 35kts. Have increased the winds above guidance due to the cold air advection which is usually underestimated. Higher end gales are possible late Friday. Winds will decrease Saturday as high pressure builds in. SCA likely needed by Sunday ahead of the next approaching system. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Gale Watch from Friday morning through late Friday night for ANZ150-152-154. && $$ SYNOPSIS... NEAR TERM...Legro SHORT TERM...Cempa/Legro LONG TERM...Curtis AVIATION...Curtis/Legro MARINE...Curtis/Legro

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