Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 150320 AAC AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 1020 PM EST Sun Jan 14 2018 .SYNOPSIS... High pressure will build over the region this evening before cresting over the area on Monday. However, a weak trough may bring a few flurries or widely scattered snow showers to the southern coastline. Low pressure will approach from the west Tuesday before crossing northern New England Tuesday night and Wednesday. Low pressure will form off the Mid Atlantic coast Thursday, but will pass well out to sea Thursday night. Canadian high pressure will build back over the region Friday. A warm front will then cross the region, bringing mild temperatures next weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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Update...Forecast looking on track...just minor tweaks to temps and dewpoints. Previous discussion...Mainly clear skies expected over most areas overnight along with relatively light winds. This will allow for radiational cooling, leading to very cold temperatures overnight. Expect temperatures to bottom out to as cold as 20 below zero overnight in the northern mountains. Areas to our north and west last night reported readings similar to this value. Went a few degrees below most guidance for the overnight lows. Along the coast, there may be periods of high cloudiness associated with an offshore system. There may also be some gradient winds for a brief period along the coast allowing for mixing and slightly milder temperatures. Nevertheless, expect readings near zero even along the beach communities. Enough dry air in place to prevent fog from forming most areas.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... A weak inverted trough will form on Monday as low pressure moves well out to sea south and east of our area. This trough, along with a second upper level trough will bring clouds to the region tomorrow. Much of it will be mid and upper level moisture, however low clouds are expected along the coast. Along the immediate shoreline, a few light ocean effect snow showers are possible. As a cold wedge of air remains over the region from high pressure to our north, have forecast temperatures only in the teens to lower 20s over Maine and New Hampshire. Clouds will thicken Monday night with the approach of a large upper level trough of low pressure. A few scattered snow showers may make their way into New Hampshire by late at night although the atmosphere will be initially very dry in many areas. && .LONG TERM /TUESDAY THROUGH SUNDAY/... A positively tilted long wave trof digs southeast through the Great Lakes Tue. This will allow a southwest flow to develop to the east of the trof with some overunning to develop well east of the system. Clouds will be on the increase Tue with some weak WAA overrunning light snow to develop from southwest to northeast Tue afternoon and night. As this trof moves east models differ on solutions. Will stick with a blend of models suggesting a weak wave of low pres will develop off the mid atlantic coast and then move through the Gulf of Maine Wed. Generally light amounts of QPF with this system so not expecting any major snowfall...but several inches may occur with highest amounts closer to the coast. PTYPE will be all snow as temp profiles suggest. The trof quickly exits to the east by Wed night allowing clearing with a brief shot of cold air in its wake. On Thu a more zonal flow aloft develops allowing a warmer return flow to develop that will continue into the weekend. Several minor short waves that will be hard to time will move through the zonal flow aloft and may give a few rounds of light precipitation mainly to the mountains with only a chance of a few showers over southern areas. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... Short Term...Mainly VFR conditions. The exception will be Portland, Portland and Rockland as well as other areas along the coast Monday as low clouds pour in off the Gulf of Maine. Long Term...Snow will overspread the area W-E Tu afternoon and evening and will continue into Wed. Conditions will lower to MVFR late Tue and MVFR to IFR Tue night and Wed. Conditions improve by late Wed with VFR conditions Wed night into Fri. && .MARINE... Short Term...Have issued SCAs for seas, and at times winds through Monday night. Have also issued freezing spray advisories for eastern areas. Long Term...A storm system well offshore could continue the 5-7 ft swells offshore through Tue. Winds will be light Tue through Fri. && .HYDROLOGY... There are still Ice jams on several rivers in New Hampshire and Maine. However, we are beginning to see the last of the water from rain and snowmelt of the last few days and overall flows are declining. This has lowered some rivers below flood stage despite the ice jams, and lowers the threat for flooding. With very cold temperatures expected for a few days, some ice jams may freeze in place, and water will continue to run high in these areas. A flood warning will remain in effect through tonight for the Kennebec River at Augusta and the Connecticut River at North Stratford. Ice jam flooding will continue through the evening at North Chichester. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Freezing Spray Advisory until 6 PM EST Monday for ANZ150>153. Small Craft Advisory until 6 AM EST Tuesday for ANZ150-152-154. Small Craft Advisory from 6 AM Monday to 6 AM EST Tuesday for ANZ151. && $$ NEAR TERM...Legro is the U.S. government's official web portal to all federal, state and local government web resources and services.