Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 261533 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1133 AM EDT Wed Jul 26 2017 .SYNOPSIS... High pressure will become centered over the area today and move offshore tonight. A cold front moves across the area on Thursday bringing scattered showers and thunderstorms. High pressure will attempt to build into the region Friday and into the weekend as low pressure moves south of the area. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Update...Have updated the forecast based on latest conditions. Fog has dissipated in all areas, however a Cu field has taken its place. Still, this will leave the region with mainly sunny skies, light winds and seasonable temperatures. Have adjusted max temperature forecast up a couple degrees for this afternoon. Thursday appears to be more active with scattered showers and storms. A few of the thunderstorms may contain damaging winds and hail. The marginal risk has been expanded to include our entire forecast area. Previous discussion...Widespread fog in the river valleys...dense at times...will lift and dissipate quickly as daytime heating gets underway. High pressure will be in control...allowing for sunny skies and light winds. High temps should be able to climb into the 80s for most...except cooler in the mtns...and near the coast where weak pressure gradient will allow for sea breezes to develop.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... An approaching s/wv trof and attendant cold front will approach the region tonight. An initial area of showers and decaying storms will lead the main s/wv trof. These are forecast to move into the area late tonight and early Thu. I expect these will mainly stay in the mtns...and be on the light side. Then the focus is on how much clearing occurs in the wake of morning showers. Lapse rates will be marginal...but dew points will be increasing on return flow behind high pressure. Pockets of heating should allow for sufficient CAPE for thunderstorms development along the cold front itself. With a H3 jet streak crossing the region...shear will be more than adequate for organized updrafts...especially the Srn part of the forecast area. So given that we can get breaks in the clouds...storms should form and some of these will likely organize into stronger clusters. SREF calibrated severe storm probabilities have increased over the last several runs...and extended HRRRX shows a fair amount of convective development by Thu afternoon. Considering these recent trends...and SPC marginal risk for severe storms...I have included gusty winds/small hail during Thu afternoon. With the loss of diurnal heating...storms should wind down fairly quickly around sunset. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... A cold front moves offshore Thursday evening with scattered showers and and thunderstorms...by late evening the front moves offshore allowing clearing to develop behind the FROPA. High pressure builds into the region Friday and Friday night while low pressure develops along the southern New England coast. Models generally agree on keeping the northern fringe of any rain along or just south of the NH and ME coastline. There could be a brief period of some light rain reaching these areas late Fri night into early Sat if the track shifts slightly north. Most areas north and west of the coast Sat will likely remain partly to mostly sunny. By late Sat the system quickly exits to the east allowing high pressure and a warmer more zonal flow aloft to develop for the last half of the weekend and into next week. Temps will comfortable Friday and into the weekend with highs in the 70s to near 80 but by early next week highs in the 80s can be expected with an increase in humidity. && .AVIATION /16Z WEDNESDAY THROUGH SUNDAY/... Short Term...LIFR conditions will continue in the major river valleys...especially across NH thru sunrise. Clear skies will allow for daytime heating to quickly lift and dissipate fog...with VFR conditions expected into the late evening. An approaching cold front will spread some scattered SHRA thru the area early Thu...but these should remain VFR or MVFR. The cold front itself may spark some afternoon TSRA. Based on morning precip and model trends...the best chance for TSRA and perhaps a stronger one or two would be across the Srn half of NH. However confidence is not high enough to include in TAFs at this time. Long Term...MVFR conditions possible in evening showers and scattered tstorms associated with the passage of a cold front Thu evening, otherwise mainly VFR conditions through the outlook period. && .MARINE... Short Term...High pressure in control today will keep winds and seas below SCA thresholds. Return flow behind the departing high on Thu will allow for seas to build. It is possible by afternoon some 5 ft seas could occur...but mainly out by Jeffreys Ledge. Long Term...Seas and winds remain below small craft advisory levels Thursday night through Friday night. Winds and seas may briefly approach SCA conditions Saturday depending on the exact track of low pressure that passes southeast of the area. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ JC

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