Area Forecast Discussion
Issued by NWS Portland, ME

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260 FXUS61 KGYX 121826 AFDGYX Area Forecast Discussion National Weather Service Gray ME 226 PM EDT Sat Jul 12 2025 .SYNOPSIS...
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An airmass with high humidity over the area will linger into Sunday. Look for a chance of a few showers or a thunderstorm during peak heating tonight. A cold front will near the region on Monday with widespread showers and thunderstorms, some of which could produce locally heavy rainfall. Drier weather returns Tuesday, with heat and humidity building in for the rest of the week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Stagnant pattern with weak onshore flow continues to keep stratus over the coast through the foothills today and tonight. There will be some breaks of sun through mid to late afternoon, but expect overnight conditions to again thicken and lower with fog redeveloping. To points north of the mountains, a mostly sunny day is underway with the warmest temps in the forecast area. Shower and storm activity is still expected this afternoon and early afternoon, boosted by daytime heating in mostly sunny areas. With no prominent lifting feature, showers/storms may anchor themselves on terrain initially, before drifting in weak steering flow. Based on morning showers that went through southern ME, these slower moving cells will have the capability to reach 1 to 2 inch per hour rainfall rates. Combined with their slow motion, localized lowland flooding will be possible through the evening. In contrast to the previous nights, MUCAPE dwindles over the CWA tonight. This should limit coverage of showers to this evening with activity remaining west and NW of the area. Fog builds down later tonight. Would expect dense fog to limit visibility for the coast, interior, and foothills once again.
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&& .SHORT TERM /SUNDAY/...
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Sunday begins similar to Saturday with low stratus and fog in place. Points north and west of the mountains see the best chance at sun for the morning, but again will see afternoon showers and some thunder develop. CAMs portray less shower coverage for the daytime before forcing increases Sunday night. Overnight, a cold front will advance east from the Great Lakes. Associated warm front was forecast to push through the CWA overnight, but has since weakened on eastward extent. Thus concentration of precip will remain west with just a few showers or storms passing through overnight. Increasing clouds and the passing warm front may favor a mild night. The CT Valley and southern NH may retain some daytime heat with overnight lows in the upper 60s to around 70. Otherwise, the day/night trend of fog moving in overnight continues for another day.
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&& .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
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Key Messages - Flash flood risk Monday with frontal passage - Steamy hot/hazy summer days starting Tuesday - Mainly hit/miss (30%) thunderstorm chances mid-late week Monday will start off with a cold front approaching from the north. This feature combined with weak but sufficient dynamics will touch off scattered showers and thunderstorms, higher chances near the international border, and mainly after 17Z. Generally looking at weak dynamics with SBCAPE ~600 and bulk shear 10-20 knots. PWAT values >1.75" (2 standard deviations above normal) with the potential for pooling ahead of the front pushing PWATs to 2". This will make for more concerns over heavy-rainers than for severe weather. The relatively weak flow suggests some slow- moving storms, and the corfidi vectors favor regenerative propagation and set-up for training. WPC has much of the area outlooked in a marginal for Monday, despite models not depicting much QPF at this time. Believe there could be local amounts of 2-3", but if the pattern holds I wouldn`t be surprised to see upwards of 4" on a very localized basis. We`ll continue to highlight heavy rain potential in the grids and in our Hazardous Weather Outlook. Once the frontal passage clear the area there will be a brief drop in humidity going into Tuesday. Looking a plentiful sunshine which will allow temps to rise into the upper 80s to low 90s for most areas. The expansion of the summertime upper ridge and the Bermuda high will dominate the weather across much of the east coast for much of the work week. This pattern will favor a return to summertime hot and hazy days. A progressive zonal flow regime late week will likely bring scattered showers and thunderstorms, but timing of these weak features is difficult this far out. Have stuck with the typical diurnal risk windows in the afternoon until conditions become clearer. Overall, Tuesday looks to be the best chances for dry weather, while Friday could see the more widespread showers and storms as another surface cool front approaches.
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&& .AVIATION /17Z SATURDAY THROUGH WEDNESDAY/...
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Short Term...Some breaks in the clouds will offer a window of MVFR to VFR conditions along the coast this afternoon. SHRA and TSRA develop mainly along the western and northwestern borders this afternoon and evening. Overnight, a return to IFR and LIFR is expected for most terminals along the coast and interior. Sunday begins similar with a slow improvement in vis before ceilings break even slower. Coastal terminals may remain IFR for an extended period. Less SHRA coverage Sunday and Sunday night. Long Term...Stratus/fog possible again on Sunday night into early Monday, however an approaching cold front will limit the extent and duration. Heavy rain with IFR conditions possible with scattered showers Monday, then improving to VFR under sunny skies Tuesday. Mainly VFR thereafter.
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&& .MARINE...
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Short Term...Below SCA conditions as onshore flow continues. Expect marine stratus and fog to continue over the coastal waters, limiting visibility at times. Long Term...Expect similar to above through much of the work week. Winds with the initial cold front Monday night washout out so apart from light and variable there are no notable wind shifts. Looking at predominant S/SW/SE winds throughout the forecast, with waves 2` with a 7-8 sec swell.
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&& .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Cornwell SHORT TERM...Cornwell LONG TERM...Jamison