Area Forecast Discussion
Issued by NWS Portland, ME

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144 FXUS61 KGYX 171927 AFDGYX Area Forecast Discussion National Weather Service Gray ME 327 PM EDT Mon Jun 17 2024 .SYNOPSIS...
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A warm front will continue to lift through the area this evening, which will be followed by a stretch of very hot and humid conditions through the week. Record high temperatures and potentially dangerous heat index values are possible. A weak cold front will slowly cross through the region on Thursday and Friday with an increasing chance for scattered showers and cooler temperatures this weekend.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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A warm front that was forecast to lift through the area today has slowed resulting in more cloud cover across the region this afternoon. This front will continue east this evening with cloud cover thinning SW to NE this evening. Heights will build over the region tonight with return flow around high pressure offshore will set up a warm air advection regime over the Northeast. Lows tonight will generally be in the 60s with patchy fog.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
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Tuesday will mark the start of a hot a humid stretch of weather as high pressure remains anchored southeast of New England. Temperatures will climb into the upper 80s to low 90s by mid day with highs in portions of southern NH and interior western ME climbing into the mid 90s. Dewpoints will also be on the rise climbing into the upper 60s to low 70s. Winds will turn onshore helping to keep coastal areas cooler as temperatures drop during the afternoon. Across the interior and south of the mountains the combination of heat and humidity will bring heat index values into the upper 90s and the Heat Advisory has been expanded across interior central Maine. The building heat and humidity will also lead to building instability this afternoon. CAMs have been highlighting an area of convergence along the sea breeze boundary leading to isolated showers and thunderstorms tomorrow afternoon near the foothills with additional isolated storms possible over the mountains. Any showers and thunderstorm activity should diminish with the loss of heating Tuesday evening. The increasingly humid airmass will limit cooling Tuesday night as lows only drop into the upper 60s to around 70 degrees.
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&& .LONG TERM /TUESDAY THROUGH SUNDAY/...
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There remains little in the way of changes to the operational and ensemble solutions regarding the heat wave which continues into the long range portion of the forecast. A large ridge of high pressure will remain seated over the Northeast on Wednesday. This dome will allow H8 temperatures to climb to +20C by Wednesday afternoon under partly to mostly sunny skies. Air temperatures will climb into the mid and upper 90s over most areas with sea breezes expected along the coast. However a westerly flow aloft, albeit light, will keep the sea breeze from penetrating very far inland. Surface dew points are still expected to climb into the 65 to 70 degree range. This will allow apparent temperatures to climb to over 100 degrees at times away from the coast. It will be mainly rain- free however an isolated shower or thunderstorm will be possible over northern areas late as precipitation rotates around the periphery of the ridge. Nighttime lows will be on the warm side as well, mainly in the lower 70s. This will aggravate heat stress. The peak of the heat will arrive on Thursday as a strong upper level ridge remains centered near Long Island New York. After a warm night with patchy fog, temperatures will soar once again under a light westerly flow aloft. Widespread mid to upper 90s can be expected with a few communities, mainly in southern New Hampshire exceeding 100 degrees. Relatively high dew point values will allow for apparent temperatures to climb into the 100 to 105 degree range, very near to the Excessive Heat Thresholds. Scattered showers and thunderstorms will once again rotate around the periphery of the ridge and mainly be centered over northern areas. A weak front will then be draped over the region on Friday. It will be about 10 degrees cooler than on Thursday, mainly due to the increased cloud cover and the scattered showers and storms across the forecast area. Slightly lower dew points can be expected which will be an ongoing trend into the weekend. A nearly stationary front will allow for scattered showers and thunderstorms throughout the weekend.
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&& .AVIATION /17Z SUNDAY THROUGH THURSDAY/...
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Short Term...Increasing moisture will bring some potential for restrictions in fog tonight with the highest probabilities along the CT Valley and central Maine. Otherwise, VFR likely prevails tonight through Tuesday. Isolated TSRA will be possible Tuesday afternoon mainly along the foothills with KAUG being the TAF site with the highest likelihood of seeing brief restrictions. Patchy fog will again be possible Tuesday night. Long Term...Mainly VFR conditions through Wednesday followed by more showers and thunderstorms with a cold frontal passage by late Thursday into Friday. Areas of IFR conditions are possible as well during the night time period with patchy valley fog and associated with more scattered showers and thunderstorms throughout the weekend.
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&& .MARINE...
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Short Term...A warm front lifting through the waters while high pressure becomes centered southeast of the waters will bring S to SE winds with gusts around 20 kts through this evening. Winds relax tonight with winds and seas remaining below SCA thresholds Tuesday through Tuesday night. Long Term...Winds and seas will primarily be out of the south during the extended portion of the forecast and below SCA thresholds. Highest wind gusts likely will be during the afternoon hours as the sea breeze attempts to form. The winds will briefly become westerly on Friday.
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&& .CLIMATE...
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Record breaking high temperatures and warm overnight low temperatures are likely Tuesday through Friday of next week. Here are the records... RECORD HIGHS FOR JUNE 19: Concord-98, 1995 Augusta-98, 1995 Portland- 94, 1995 RECORD HIGHS FOR JUNE 20: Concord-98, 1993 Augusta-95, 1953 Portland- 93, 2020
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&& .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Heat Advisory from noon to 8 PM EDT Tuesday for MEZ012>014- 018>021-033. Excessive Heat Watch from Wednesday afternoon through Thursday evening for MEZ012-018>020-033. NH...Heat Advisory from noon to 8 PM EDT Tuesday for NHZ004>013-015. Excessive Heat Watch from Wednesday afternoon through Thursday evening for NHZ006-008>010-012-013-015. MARINE...None.
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&& $$ NEAR/SHORT TERM...Schroeter LONG TERM...Cannon