Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 190319 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1119 PM EDT Tue Oct 18 2016 .SYNOPSIS... A warm front will lift northeast across the area tonight while a cold front sweeps in from the northwest. A few showers will be possible as this moves through. Expect warm weather on Wednesday as an offshore wind brings dry air and a clearing sky, especially to the south and east of the mountains. High pressure slides across northern New England Wednesday night and into the Canadian Maritimes on Thursday. Meanwhile, low pressure developing over the Ohio Valley will track northeast toward northern New England by Friday. This will bring a period of wet weather from late Thursday through Friday night when a cold front pushes through from the west. This front will bring colder weather for the weekend into early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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1115 PM Update...Have cancelled a portion of the dense fog advisory close to the MA border as the warm front continues to progress northward. The rest remains in effect until 1 am. 9 PM Update...Have issued a dense fog advisory for southeastern NH and York County ME until 1 am. Visibilities have dropped to a 1/4 mile or less in this area. While the warm front is on the doorstep just to the south, the cool moist low level marine layer is going to be tough to dislodge through midnight. Otherwise, no significant changes to the forecast. 615 PM Update...Have updated the forecast mainly to account for latest trends in observational data. Cold air damming continues across much of the region except for W/SW fringes of the CWA. The SFC warm front will be slow to move now that it is nighttime and have therefore adjusted temperatures for the next few hours based on this philosophy. Otherwise, areas of drizzle and fog will continue on the coastal plain this evening and into the overnight hours. Previously... Cold air damming continues to hang on across a large part of the area south of the mountains, with clouds, fog and some drizzle for the rest of the afternoon. The warmer and drier air is making some inroads in parts of srn NH and the CT vly, and will see some clearing and a brief warm up[ before sunset in these areas. The Merrimack valley is the biggest question as if it does break out before sunset temps could pop up close to 70. Areas that do break into the surface warm sector will see temps fall off a little bit this evening, but anyplace thats stuck in the inversion will likely see the overnight min occur at sunset as temps will begin to slowly rise overnight as the warm sector moves in and southerly winds pick up a bit. This should eventually clear out the fog and the low clouds in a lot of spots overnight. Cold front could produce some SHRA in the north as well, but unlikely to the south. Front should move into the north toward daybreak and cross the coast shortly after sunrise.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... West winds combined with warm air loft will allow the downslope to warm the area quite nicely for Oct 19, with highs in the 70s outside the mountains, and in the mid to upper 60s there. Could see a run at 80 in the Merrimack valley. Any morning clouds in the mountains will dissipate by midday with mainly sunny skies everywhere. Should be enough flow persisting into the night to prevent full rad cooling, so lows will still be above normal, in the upper 30s N to mid to upper 40s in the south, but definitely cooler than previous nights. Look for mid to high clouds to begin to roll in from the west after midnight. && .LONG TERM /THURSDAY THROUGH TUESDAY/... High pressure moving into the Canadian Maritimes and low pressure developing over the Ohio Valley will begin an onshore easterly flow over much of New England on Thursday while high level cloud cover moves in from the southwest in advance of an approaching upper level trough. Models are in better agreement than they were at this time yesterday on the way this trough and its relevant surface features will evolve, with the surface low tracking through northern New England before merging forces with a weak tropical low racing northward off the East coast. The resulting low will then pull northward into the Gulf of Saint Lawrence while a sharp upper level trough lingers in its wake over New England through the weekend and into next week. On Thursday, expect cooler conditions with increasing clouds and an onshore wind developing. This should keep temperatures in the 50s for most of the area, with rain showers beginning in the afternoon especially in the north and west. A warm front tries to lift north across the area Thursday night into Friday, though the flow will still be onshore for most of the region, holding temperatures in the 60s with abundant cloud cover. By this time, the onshore flow could even lead to areas of drizzle developing near the coast while the more persistent rain lifts north into Canada. On Friday, low pressure moving into northern New England from the west joins forces with low pressure moving north off the East coast, spreading rain through the region. With the tropical connection here, it is possible that some of the rain could be heavy though flooding is unlikely. Low pressure moves into northeast Maine by Saturday morning, with the more persistent rain moving east with it and a cold front sweeping in beneath it. Should see colder temperatures beginning on Saturday as cold air gets drawn in behind the system. Could see some lingering showers mainly in the mountains, which may eventually transition to snow showers as the cold continues to pour in Saturday evening. Upper level trough is slow to depart, keeping New England in a cold northwesterly flow. This will keep daytime highs in the 40s and low 50s. Nighttime lows will be in the 20s and 30s, though persistent northwest winds may prevent ideal radiational cooling conditions until the surface high arrives midweek. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... Short Term...Expecting improvement at terminals, to at least MVFR later tonight as southerly winds begin to pick up and break the inversion. Until then we expect dense fog. Could see the valley locations go down briefly to IFR toward daybreak. All terminals will see VFR shortly after sunrise on Wed, which will persist through Wed night. Long Term...Expect increasing clouds Thursday, primarily from the top down. Conditions may become MVFR to IFR Thursday night as onshore flow persists in bringing in low level moisture. More substantial rainfall is possible on Friday and Friday night as low pressure moves through the area, likely keeping conditions IFR or worse for most of the time. A cold front pushes east through the area Friday night into Saturday morning, helping to clear out some of the clouds and potentially bring VFR conditions again south of the mountains. North of the mountains, lower clouds and rain/snow showers may persist through the weekend. && .MARINE... Short Term...Expecting a surge SW winds ahead of a cold front this evening, and SCA will remain up for gusts of 25-30 kts, which will diminish towards daybreak. No SCA conditions expected Wed and Wed night. Long Term...East to southeasterly flow ahead of low pressure moving through northern New England should stay near or below advisory levels, but the onshore nature of the wind will allow wave heights to build to over 5 FT. A cold front pushes east across the waters early Saturday morning, with a west to northwesterly flow behind it which will likely gust above 25 KT at times. && .TIDES/COASTAL FLOODING... && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Dense Fog Advisory until 1 AM EDT Wednesday for MEZ018-023. NH...Dense Fog Advisory until 1 AM EDT Wednesday for NHZ008-010. MARINE...Small Craft Advisory until 8 AM EDT Wednesday for ANZ150>152- 154.
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