Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 210712 AFDGYX Area Forecast Discussion National Weather Service Gray ME 312 AM EDT Wed Jun 21 2017 .SYNOPSIS...
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A weak cold front will cross the area today accompanied by scattered showers, and maybe a few thunderstorms mainly across central and northern sections. High pressure follows the front for tonight and Thursday with dry air and seasonable temperatures. A more significant storm system approaches for late Thursday night and Friday. A series of weak cold fronts or surface troughs will bring unsettled weather at times this weekend into early next week.
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&& .NEAR TERM /THROUGH TODAY/...
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At 06z...GOES water vapor imagery showed a shortwave impulse over the eastern Great Lakes. An associated surface trough/weak cold front was draped along the Interstate 81 corridor of upstate New York. NWS Doppler radar mosaic showed a line of broken convection along and ahead of this weak boundary. For today...the impulse will race east and cross the forecast area by afternoon. The weakening upstream convection will cross the area during the morning and early afternoon hours. Daytime heating will likely generate some additional convection but moisture and and instability are limited so not anticipating any strong convection today. Highs today will be in the upper 70s and lower 80s..but near 70 along the international border and along the mid coast of Maine in an onshore trajectory.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM THURSDAY/...
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Behind the departing shortwave...weak ridging and drier air arrives for tonight. It`ll be a comfortable sleeping night with lows mainly in the 50s...with some upper 40s in the normally cooler mountains valleys near the international border. We`ll see a mostly sunny and mild day on Thursday as the weak ridge remains across the forecast area with some late day high and mid clouds heralding the approach of our next disturbance from the Great Lakes. Highs will be in the upper 70s and lower 80s...but a bit cooler once again near the international border and along the mid coast of Maine.
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&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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Weak troughing will be replaced by ridging Thursday night into Friday. An area of high clouds associated with the jet stream will be across northern sections of the forecast area initially but these will thicken and lower during the day. At the surface low pressure will track north of the forecast area with a warm front spreading showers across the region during the morning hours. We remain in the warm sector for much of the day with southerly winds boosting moisture and temperatures, with most spots warming into the 70s to even upper 80s across southern NH. This will set the stage for widespread thunderstorms as a cold front marches from northwest to southeast in the evening. Quite a bit of shear is forecast along with ample instability to perhaps result in some rotating storms capable of damaging winds and large hail and even a tornado. This could be tempered by the fact that the best forcing for ascent could arrive later in the night...also cloud cover from earlier convection may cause some issues with insolation. An elongated band of vorticity will affect the region Sunday into Monday as large scale troughing digs into the Great Lakes region. This will keep clouds and showers over the area...especially over the northern sections. Over the weekend we will see some cooling of high temperatures into the lower to mid 70s north to lower 80s south. The upper low begins to open up and eject eastward into the Canadian Maritimes around midweek. Once again the proximity of the cyclonic flow will keep clouds and showers in the cards, especially farther north. Temperatures will continue a slight decline but should hover in the upper 60s to upper 70s for highs Tuesday into Wednesday.
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&& .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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Short Term /Through Thursday/...VFR with sct brief MVFR psb today in -shra and isold -tsra. Long Term...VFR conditions expected Thursday night. MVFR to IFR conditions will develop Friday and continue into Saturday morning. VFR conditions will return during the day Saturday and should persist through Sunday.
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&& MARINE... Short Term /Through Thursday/...SCA dropped for the waters as seas continue to diminish. Winds and seas will increase today ahead of the weak cold front...and we may briefly approach SCA conditions outside the bays over our eastern waters during the afternoon. Long Term...Friday seas increase ahead of a frontal system and should reach SCA criteria for both seas and winds. Seas will stay up longer perhaps thru Sunday morning with winds subsiding fairly quickly. && .TIDES/COASTAL FLOODING...
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The period of monthly astronomical high tides will continue through the upcoming weekend and into early next week. Projected tides will be within 1.0 ft MLLW of flood stage along the coast for the high tide centered an hour or two either side of midnight each night. So, it won`t take much in the way of onshore flow or wave action for potential coastal flood or splashover issues along the coast. At this time, the greatest threat appears to be Friday night.
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&& .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...None. NH...None. MARINE...None.
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&& $$ SYNOPSIS...Schwibs NEAR TERM...Schwibs SHORT TERM...Schwibs LONG TERM...Hanes AVIATION...Schwibs MARINE...Hanes/Schwibs TIDES/COASTAL FLOODING...Schwibs

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