Area Forecast Discussion
Issued by NWS Portland, ME

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442 FXUS61 KGYX 130625 AFDGYX Area Forecast Discussion National Weather Service Gray ME 225 AM EDT Sun Jul 13 2025 .SYNOPSIS...
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An airmass with high humidity over the area will linger today. There is a chance of a few showers or a thunderstorm during peak heating this afternoon and early evening. 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 TODAY/...
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Nighttime microphysics satellite imagery early this Sunday morning shows a plethora of low-level stratus over most of the region south of the mountains. These low ceilings are resulting in fog in many locations, some of which has become locally dense. Fog and reduced visibility will prevail through this morning along with patchy drizzle at times. Current temperatures are primarily into the 60s and little in the way of additional cooling is expected through sunrise. Today will feature another overcast and foggy start to the day before clouds begin to scatter out late morning and into the afternoon across northwestern ME and interior NH while the stratus deck lingers a few hours longer over southwestern ME south of the foothills along with the Seacoast of NH. High temperatures will range from the 70s over much of western ME with lower to middle 80s in interior NH. A few scattered showers and storms are possible during the afternoon and evening, mainly from the mountains and points north. These could produce locally heavy rainfall but the overall hydro threat is low due to the isolated coverage that is expected.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM MONDAY/...
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The H5 s/wv ridge axis will begin to drift east tonight ahead of an area of low pressure and associated cold front to our west. At the surface, onshore flow will prevail, leading to additional low ceilings and fog. Scattered showers and rumbles of thunder will remain possible across the mountains and towards the Canadian Border but most other locations should remain dry. Low temperatures will be mainly into the lower to middle 60s. Low pressure lifting northeast through Quebec will drag a cold front across the area Monday. The airmass ahead of the front will be moisture rich with dewpoints nearing 70 degrees and ensembles showing PWATs approaching 2 inches. The front and mid level support will be weakening upon approach, although look to be enough to trigger scattered thunderstorms across the area with the highest PoPs during the afternoon. Deep layer shear will be modest around 30 kts across northern zones with shear diminishing south of the mountains. The best juxtaposition of shear and instability looks to remain north and west of the area while model soundings suggest that there could some strong to marginally severe storms across northern zones with CAMs showing a weakening trend as storms slowly track SE into the coastal plain Monday night. Given the recent isolated heavy rainfall experienced across SW New Hampshire within the present airmass, the greater impact from thunderstorms on Monday will be the threat for torrential rainfall. Multiple ingredients look to be in place with PWATs nearing +2SD and deep warm cloud depths greater than 12kFT. In addition, flow looks to be parallel to the frontal boundary with small Moe velocity vectors. This would support slow moving storms and the potential for training. Both the 00Z HRRR and NAMnest suggest storms will be capable of rates approaching 1-2 inches per hour and any training of these rates will bring the risk of flash flooding. Otherwise, Monday will be mostly cloudy and humid with highs in the 70s to mid 80s. Onshore flow and stable marine air will limit the threat of thunderstorms along the coastal plain.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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Key Messages - Steamy hot/hazy summer days starting Tuesday - Mainly hit/miss (30%) thunderstorm chances mid-late week Once the frontal passage clears the area there will be a brief drop in humidity going into Tuesday. There will be 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 chance for dry weather, while Friday could see more widespread showers and storms as another surface cool front approaches.
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&& .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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Short Term...Low ceilings and FG will continue through around 12-15Z today before scattering out to VFR/MVFR later in the day. KRKD may remain at IFR though through much of the day. Scattered SHRA/TSRA is possible after 16Z at KHIE and KLEB. Winds will be out of the south at 5-15 kts. Marine stratus returns this evening and lingers through Monday morning, bringing additional flight restrictions. Slow improvements are then likely again later Monday before more widespread SHRA and TSRA arrive during the afternoon and evening with southeasterly flow. No LLWS is anticipated outside of any TSRA. Long Term...Conditions improve to VFR under sunny skies Tuesday. Mainly VFR thereafter.
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&& .MARINE...
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Short Term...South-southeasterly flow will prevail through the period at 5-15 kts and seas of 1-3 ft. Marine fog will continue to be common, especially at night and during the morning and evening hours. 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...Tubbs SHORT TERM...Tubbs/Schroeter LONG TERM...Jamison/Schroeter