Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 230133 AFDGYX Area Forecast Discussion National Weather Service Gray ME 933 PM EDT Tue May 22 2018 .SYNOPSIS... Showers will end tonight as weak low pressure and an associated frontal system slide offshore. A cold front will drop south across the area on Wednesday producing scattered showers and a few thunderstorms across northern and mountain sections. High pressure will build into the region Thursday. The next weather maker nears the northeast for the weekend. && .NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/...
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---930pm Update--- Still some scattered showers moving across the forecast area this evening, but they are diminishing in both areal coverage and intensity. They should be just about finished up within a few hours after midnight. Still expect there to be some areas of fog that develop and relative humidity values are now creeping up above 90% in some locations. Timing on the fog still looks good, with development occurring after midnight. Only minor tweaks to the forecast for this update. ---710pm Update--- Forecast package is largely in good shape this evening. Showers continue to progress across the forecast area and are mainly scattered in nature. Forecast of up to about two tenths of an inch look really good. With low level moisture and radiational cooling in place for the night, expect fog to develop in several locations. Do not think it will be thick enough or widespread enough for a dense fog advisory, but will monitor trends as the evening progresses. Previous discussion... At 18z a 1013 millibar low was over Lake Ontario with a warm front extending eastward through central New England and a trailing cold front through the upper midwest. NWS Doppler Radar mosaic showed a large area of showers in advance of this disturbance overspreading the remainder of the forecast area at moment. For tonight...showers will end from west to east as the system exits the coast with patchy fog developing in the predawn hours.
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&& .SHORT TERM /7 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... On Wednesday...a cold front over Quebec will drop south and cross the area during the afternoon and early evening hours. The best moisture and instability will be confined to our northern and eastern Maine zones where a few showers and thunderstorms will develop by afternoon. Elsewhere...a mostly sunny day with westerly downslope flow will boost temperatures into the 70s and lower 80s. Convection ends quickly tomorrow evening with loss of heating and upper support. Should be mainly clear tomorrow night with some patchy late night fog developing. && .LONG TERM /THURSDAY THROUGH TUESDAY/... A warm front is expected to approach northern New England on Thursday from the west. There is relatively good model consensus within the 12Z run in the timing of the front which appears to be late Thursday night. Ahead of this boundary, temperatures will be relatively seasonable for this time of the year with the coolest readings and onshore winds along and near the coastline. This front will be relatively moisture starved as it crosses the region. It will introduce much warmer and more humid air. H8 temperatures will run close to +14C and with ample sun, temperatures should easily climb into the 80s in all areas except the Midcoast region. There will be a greater chance for showers on Saturday as the front begins to slip back southward as a cold front. Additional moisture and instability may yield a thunderstorm or two, mainly over southern New Hampshire during the afternoon and early evening hours. By Sunday, this front will be in full retreat, slipping to the southern New England coastline. A northeast flow will develop over the region, keeping temperatures mainly in the 60s which is significantly cooler from Saturday`s highs. Showers and perhaps patchy drizzle and fog may form over the region with similar conditions lasting into Monday. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... Short Term /through Wednesday Night/...Areas of MVFR through tonight in -shra with lcl IFR psb in fog. Becoming VFR throughout aft 13z Wed. Sct MVFR developing btw 16z and 22z Wed in shra and isold -tsra from Northern third of New Hampshire through central Maine with a cold front. Aft 22z becoming VFR throughout with lcl mvfr psb aft 08z Thu in fog. Long Term...VFR with high pressure dominating through Friday. A frontal system will bring lowered ceilings on Saturday in scattered showers and possibly a thunderstorm. Low ceiling and areas of MVFR conditions will continue into Sunday as the frontal system slips south of our region. && .MARINE... Short Term /through Wednesday Night/...Winds and seas expected to remain below SCA level throughout the period. Long Term...Winds and seas will be increasing to SCA thresholds along and behind a frontal system Thursday night into Friday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ Pohl

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