Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 280425 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1225 AM EDT THU JUL 28 2016 .SYNOPSIS... A weak frontal boundary will drop south out of Canada and into northern New England Thursday, bringing a chance for showers and thunderstorms as it does so. The front slowly slips offshore on Friday as low pressure track easts along the front offshore of Cape Cod. This will bring another chance of showers Friday into Friday night. Cooler, more seasonable temperatures return for the weekend with dry conditions. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Update... Have updated the grids based on current conditions. Lowered min temperatures overnight by a degree or two outside southern NH. Otherwise, very little change to the forecast package. Convection will be slow to cross the forecast area tomorrow afternoon and evening. Prev Disc... 6pm update...just a minor update for current conditions. Decreased the areal coverage of overnight fog to focus on the favored valley locations as the dewpoints have generally mixed out a bit more through most of the area. High pressure will continue over the region tonight allowing another warm humid night with fair weather. With calm winds and generally mostly clear conditions some patchy fog will develop after midnight. generally used a blend of models which were in general agreement for overnight min temperatures. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... On Thursday scattered showers and thunderstorms will develop first over northern and western areas of Maine and New Hampshire and then will gradually spread southward to the coastline by evening. By Thursday night, the front will become quasi-stationary along the coastal waters with showers and thunderstorms continuing along and north of the front. The best chance for any thunderstorms will be primarily early in the evening. We are not expecting any of the storms to become severe due to poor dynamics with the system. Temperatures will be hot once again over southern areas Thursday reaching the upper 80s to lower 90s. Further north in the mountains temperatures will be cooler ranging from the upper 70s to lower 80s due to the developing cloud cover and convection. Another warm muggy night is also expected Thursday night due to the lack of any ventilation of cooler or drier air. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... On Fri we will be dealing with a s/wv trof lifting out of the TN Valley and towards the Srn New England coast. There is strong model consensus on coastal low pres developing and moving very close to the elbow of Cape Cod. With that in mind I will increase PoP for much of the Srn half of the forecast area during the day Fri. Another thing to keep an eye out for will be the heavy rnfl potential. On the NW side of the low pres model guidance has a strong frontogenesis signal...especially for this time of year. With warm cloud depths on the order of 12,000 feet or more...rnfl could be quite efficient in places. I have added heavy rnfl wording to the grids for Fri. At this time the best potential will be over Srn zones...which may actually be welcomed for relief from the dry wx. After Fri the pattern looks to be dominated by an Ern CONUS trof. With the Wrn CONUS ridging also being flattened...the Nrn stream could be more active and lead to more unsettled wx. It was hard to find a day where PoP could be completely removed from the forecast...and so most days have a chance for showers/t-storms. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... Short Term...VFR conditions are expected tonight, except for perhaps a few hours of patchy areas of fog 06z-11z. VFR conditions Thursday become MVFR in developing scattered showers and thunderstorms in the afternoon and evening. Long Term...Fri may see an extended period of MVFR conditions as a coastal low pres system brings an area of rnfl to Srn zones. This would be most likely to affect MHT...PSM...PWM...and RKD. Even CON and AUG may be too far N to get into the heaviest precip. There is a low chance that some heavier rnfl moves into the Srn most terminals and brings local IFR conditions. VFR conditions return Fri night. Another round of MVFR showers is possible Sun night into Mon. && .MARINE... Short Term...Conditions are expected to remain below small craft thresholds through Thursday night. Long Term...Winds and seas look to remain below SCA thresholds thru the end of the period. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.