Area Forecast Discussion
Issued by NWS Portland, ME

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793 FXUS61 KGYX 272151 AFDGYX Area Forecast Discussion National Weather Service Gray ME 551 PM EDT Tue Jun 27 2017 .SYNOPSIS... A cold front will approach from the west through this evening and will likely aid in the development of showers and thunderstorms, a few of which may be strong to severe. The front will eventually move off the coast on Wednesday and will bring a few showers. A warm front will approach on Thursday and bring increasing chances of showers and thunderstorms during the afternoon and nighttime hours. Another low pressure system may affect the region on Saturday with more showers and thunderstorms. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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550 PM...Minor ESTF update to reflect the current mesonet in near term grids. Prev disc... For the remainder of this afternoon and evening, showers and scattered thunderstorms will continue. The atmosphere is not overly destabilized, however good dynamics aloft with an upper level low pressure system will allow for steep lapse rates through sunset. The primary threat is for hail, however a few stronger wind gusts are possible. The greatest threat for severe weather will be over southern portions of New Hampshire and southwest Maine where highest surface based CAPEs will be in place in conjunction with upper air dynamics. The HRRR and other mesoscale models suggest the convection will be off the coast between 00Z and 03Z. Have introduced patchy fog for late tonight with low level moisture in place. Areas that receive rainfall will also be prone to some fog.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... The upper level low pressure system will be exiting the region Wednesday. Nevertheless, sufficient moisture and instability will still be in place, albeit not nearly as much as today, to trigger a couple showers and perhaps a thunderstorm. will mainly be confined to the north and mountains. Cool, widespread 70s, below normal for this time of the year will be the highs tomorrow. Patchy fog possible as temperatures fall towards the dew point values. It will be chilly again with mid 40s to mid 50s for lows. && .LONG TERM /THURSDAY THROUGH TUESDAY/... The deterministic models remain in decent agreement on the longwave pattern into the upcoming holiday weekend. We begin the period with a low amplitude and nearly zonal flow with several difficult to time weak embedded shortwave impulses. By early in the upcoming holiday weekend...one of these upstream impulses will carve out a broad low amplitude trough centered over the eastern Plains and western Great Lakes. This trough axis will gradually migrate eastward into the Great Lakes and New England by the tail end of the holiday weekend. Of note is that during the past several model runs the deterministic models have trended towards a higher amplitude trough. In the dailies...a warm front will advance into New England Thursday and Thursday night as low pressure approaches from the Great Lakes. This east-west oriented boundary will stall across northern New England...then meander a bit north and south across the forecast area Friday through Sunday as a series of weak lows track along it. This will be an extended period of warm and humid weather...with daytime heating and passing shortwave energy contributing to several rounds of convection during the period. By early Monday...the surface boundary and higher humidity levels have been swept offshore. Rising heights and weak ridging should provide a dry day with seasonable temperatures and decreasing humidity levels to wind out the holiday weekend. && .AVIATION /22Z TUESDAY THROUGH SUNDAY/... Short Term...Expect VFR conditions to prevail for the rest of this afternoon and evening with a developing light southerly wind. Showers and thunderstorms are likely until about sunset, forming in New Hampshire and progressing eastward through the evening hours. Any areas that get significant rainfall could have a potential for fog tonight. More showers are possible on Wednesday, mainly in northern areas. Long Term... Thu - Fri...Areas of MVFR in SHRA/TSRA. Sat - Sun...Areas of MVFR in SHRA/TSRA with lcl IFR psb vcnty of the Maine coast in nighttime fog and stratus. && .MARINE... Short Term...Light southerly flow expected over the waters tonight, shifting to the west or southwest on Wednesday. Long Term... Thu PM - Sun...Small Craft Conditions are possible outside the bays. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ ES

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