Area Forecast Discussion
Issued by NWS Portland, ME

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611 FXUS61 KGYX 232232 AFDGYX Area Forecast Discussion National Weather Service Gray ME 632 PM EDT Wed May 23 2018 .SYNOPSIS... A cold front will exit the region this evening, allowing showers and thunderstorms across portions of Maine to move offshore. A warm front will approach the region Thursday before crossing the region Thursday night. This will lead to very warm conditions on Friday. A backdoor cold front drops into the region this weekend and will likely provide for some unsettled weather. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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---630pm Update--- Showers and thunderstorms have now completely fallen apart across the area. Will update the forecast to remove mention of precipitation tonight. Also, the winds have now shifted to the north across the forecast area and much drier air is streaming in. This should make for a more comfortable airmass over the next few hours. .Previous Discussion... HRRR continues to have a very good handle on the ongoing convection. The precipitation will slip off the coast over the next hour or two and diminish. A northwest breeze will follow drying conditions out across the region. There is still the possibility of light patchy fog however in the Penobscot River Valley where the heaviest precipitation fell today. Cold air advection will continue overnight. This will allow for readings to fall through the 40s with upper 30s likely in the mountains.
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&& .SHORT TERM /3 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... On Thursday a warm front will approach the region from the west. This will cross the region Thursday night with an increasing gradient and strong warm air advection above the surface during the overnight hours. The front will be relatively moisture starved. This system will be the leading edge of much warmer air to follow for late in the work week. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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A warm westerly flow will send temperatures soaring on Friday as high pressure remains south of the region. Expect most of the region to range through the 80s and will even approach 90 in far southern New Hampshire. A back door cold front will bring increasing clouds and a chance of late day showers into far northeast zones but the remainder of the forecast area will see a dry day. Cold front will sag south into northern zones Friday night and will be the focus for continued shower activity in central and northern sections of Maine and New Hampshire. Lows overnight will range from the mid 50s north to the mid 60s south. Cold front will continue to push south through the region on Saturday and will end up stalled over southern New England by late in the day. Looking for occasional showers and perhaps an afternoon thunderstorm in southern zones. Highs will range from the upper 60s to mid 70s north and will range through the 80s in the south. High pressure building in from the northeast Saturday night will set up an increasing onshore flow bringing ocean stratus into southern New Hampshire and southwest Maine. Looking for occasional showers with lows in the mid 40s to mid 50s. Although the sun angle is reaching its highest point considerable high and mid level clouds may prevent this low level moisture from burning off in inland locations on Sunday. Occasional showers will again dampen the holiday weekend. Highs will generally remain in the 50s across western Maine and lower to mid 60s in New Hampshire. Low level moisture will invade most of the forecast area Sunday night and Monday along will a continuing chance of showers. Weak shortwave moving in from the west on Monday will enhance shower activity across the region. Highs on Monday will range from the upper 50s to upper 60s. A weak cold front behind the departing shortwave will push south into northern zones Monday night and will continue south and offshore by early afternoon on Tuesday bringing sunshine and warmer temps back into the region.
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&& .AVIATION /00Z THURSDAY THROUGH MONDAY/... Short Term...VFR conditions expected tonight through Thursday night. However, there will be some patchy inland valley fog over eastern areas tonight with localized MVFR or IFR conditions along and near the Penobscot River Valley. Long Term... VFR Friday and Saturday. Areas of IFR/LIFR ceilings developing in southern zones Saturday night and Sunday. Widespread IFR/LIFR ceilings developing Sunday night and persisting through Monday night. && .MARINE... Short Term...Winds will be relatively light tonight and Thursday. However, the gradient will increase with the passage of a warm front Thursday night. Winds will likely exceed SCA thresholds at that time. Long Term... SCA`s likely on Friday. && .FIRE WEATHER... On Thursday, RH values will fall into the 20 to 25% range across most of the area away from the coast. Occasionally gusty winds will create an elevated fire danger. Friday will see gusty west to northwesterly flow around 25 kt. These winds will help to mix down dry air from aloft with RH dropping to around 30 to 40% across southern New Hampshire and possibly portions of southwestern Maine. This will put southern NH near Red Flag criteria and will need to be watched for possible Fire Wx headlines. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ Pohl

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