Area Forecast Discussion
Issued by NWS Portland, ME

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678 FXUS61 KGYX 192000 AFDGYX Area Forecast Discussion National Weather Service Gray ME 400 PM EDT Wed Jun 19 2024 .SYNOPSIS... High pressure will remain east of New England through much of this week, continuing our period of hot and humid conditions through Thursday. Record high temperatures and potentially dangerous heat index values are likely. A cold front will slowly cross through the region on Thursday and Friday with an increasing chance for scattered strong thunderstorms and cooler temperatures starting on Friday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Showers and thunderstorms, a few severe, will continue into the early evening hours per latest radar trends and latest NamNest solution. HRRR continues to have an issue deriving the convection today. This precipitation will diminish by around sunset as the atmosphere gradually stabilizes. Excessive heat today will lead towards another very warm night tonight. Last night, lows were in the lower to mid 70s in many interior areas and this will likely occur again. This sustained heat leading into tomorrow will allow for increased heat stress in buildings and areas without proper air conditioning. Patchy fog can be expected tonight, especially in areas that received heavy rainfall today. The latest HREF hints at possible maritime fog along the Midcoast region tonight by late tonight.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
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The latest 12Z operational runs and ensemble solutions continue to suggest a more westerly component to the flow on Thursday. This may delay the sea breeze along the immediate shoreline allow for hazy, hot and humid conditions all the way to the coastline for a longer period than today. In any case, this large scale upper level ridge that has been leading to the heat will still be intact. Expect apparent temperatures to reach or exceed 105 degrees in many areas once again on Thursday. Surrounding this warning, have issued Heat Advisories for the period 15Z-23Z. A front does cross through the region during the afternoon hours, a little faster than guidance has suggested. However, temperatures will soar very quickly during the morning hours to allow for high CAPE values to develop and improved dynamics along and near the passing cold front. Most of the area remains in a Marginal Risk and have included strong, gusty winds and locally very heavy rainfall in the forecast. There will be high PWATs near 2 inches in a steep low level level lapse rates leading to the severe weather potential. Patchy fog once again can be expected Thursday night. Showers will take a few more hours to diminish than today with a chance for precipitation throughout the night.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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With ongoing heat headlines and severe weather, the long term forecast was populated with the NBM, with only minor adjustments made. The heat breaks by Friday as a cold front presses southward Thursday night. Highs are mostly expected to range from the upper 70s to mid 80s. Showers and storms are likely across as least southern areas as convection rides along the front. Periods of showers and storms are likely at times through the weekend and into early next week as we find ourselves on the northern side of the ridge. Cooler conditions are expected on Saturday, but a warming trend resumes on Sunday with temps warming into the 80s and continuing into early next week. Drier conditions likely return by midweek next week as highs warm back into the low 90s.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
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Short Term...Mainly VFR conditions after the convection diminishes this evening. However, there will be the potential for valley fog. Maritime fog is possible along the Midcoast. More showers and thunderstorms, some with strong gusty winds and possible hail will return on Thursday afternoon leading to localized IFR conditions. Scattered showers and thunderstorms may linger into Thursday night. Long Term...Periods of showers and storms bring restrictions at times Friday through Monday, especially in the afternoon hours. Otherwise, mainly VFR conditions are expected. VFR conditions likely then prevail next Tuesday and Wednesday.
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&& .MARINE...
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Short Term...South to southwesterly winds will continue tonight into Thursday, just below SCA criteria. Winds back to the west Thursday night as slightly drier air enters the region. Long Term...A cold front presses southward through the waters early Friday, with high pressure gradually building in for the weekend. SCA conditions are then possible next week as southerly flow increases as the high moves offshore.
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&& .CLIMATE...
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RECORD HIGHS FOR JUNE 20: Concord-98, 1993 Augusta-95, 1953 Portland-93, 2020 RECORD WARM LOWS FOR June 20: Concord-73 in 1931; Augusta-67 in 1974; Portland-69 in 2020
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&& .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Heat Advisory until 8 PM EDT this evening for MEZ007>009- 022>028. Excessive Heat Warning until 8 PM EDT this evening for MEZ012>014-018>021-033. Heat Advisory from 11 AM to 7 PM EDT Thursday for MEZ012>014. Excessive Heat Warning from 11 AM to 7 PM EDT Thursday for MEZ018>028-033. NH...Heat Advisory until 8 PM EDT this evening for NHZ001>003-005- 007-011-014. Excessive Heat Warning until 8 PM EDT this evening for NHZ004- 006-008>010-012-013-015. Heat Advisory from 11 AM to 7 PM EDT Thursday for NHZ002>005- 007-011. Excessive Heat Warning from 11 AM to 7 PM EDT Thursday for NHZ006-008>010-012>015. MARINE...None.
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&& $$ NEAR/SHORT TERM...Cannon LONG TERM...Clair