Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 012011 AFDGYX Area Forecast Discussion National Weather Service Gray ME 411 PM EDT Fri Jul 1 2022 .SYNOPSIS...
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A very warm night is expected with showers and embedded thunderstorms increasing in coverage well after midnight ahead of an advancing cold front. This activity will continue through early Saturday afternoon before the cold front passes south of the area and much drier and cooler air returns for Saturday night. Seasonably warm temperatures will continue under high pressure for Sunday and Independence Day before another disturbance brings our next chance for showers and thunderstorms late Monday night and Tuesday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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High Impact Weather Potential: Low chance for an isolated strong storm well after midnight with local downpours/ponding of water possible. Pattern: Early afternoon water vapor imagery shows a pinwheeling upper low over Hudson Bay with a plume of moisture on it/s eastern flank moving into the northeastern United States. A cold front is moving east in association with this moisture plume and is firing convection over the eastern Great Lakes. More convection is firing along a pre frontal trough south and west of our area into the Mid Atlantic. Tonight...as the cold front approaches...our focus will be on the potential for overnight convention as a very warm and humid airmass moves overhead. Through this evening: A mix of sun and clouds with very warm temperatures attm will continue through the evening. Visible satellite imagery and area webcams showing convective towers having a tough time standing up against strong deep layer shear given modest instability with surface dewpoints still largely in the 50s. While a shower or storm could clip the area along the international border late this afternoon and into the evening...expect the area to remain mostly dry with Tonight: While the first half of the night is looking dry given the short term ensemble consensus...there is an increasing confidence that a convectively-induced vort lobe associated with evening convection over western NY and PA will move into the region well after midnight ahead of the surface cold front. There remains substantial /500-1000 J/kg/ elevated instability as this activity pushes through the region and thus expect showers and embedded thunderstorms as it arrives. Can/t completely rule out an isolated strong to severe storm as this occurs given brisk mid level flow though MUCAPES will be falling as the convection arrives. PWATs will near 1.5" with warm cloud depths moving toward 12kft. However..convective activity should have a pretty robust forward motion and will likely be in a decaying state given the time of night so outside of localized downpours/ponding...do not see a significant hydro threat overnight. The precipitation will lower temps some...but do expect a rather warm night as temperatures south and east of a AFN-CON- LEW-AUG line will likely struggle to fall below 70...and will likely remain in the mid 70s for much of the night.
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&& .SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
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High Impact Weather Potential: Isolated severe thunderstorm possible over far southern NH and southwest ME through mid afternoon Saturday. Pattern: Shortwave trough and associated cold front will be entering the forecast area as this period opens daybreak Saturday. This feature will cross the region through the morning and early afternoon providing the impetus for shower and thunderstorm activity which will be our forecast focus through the short term. By late in the day...drier air will filter in from the north and west bringing clearing skies and quieter conditions that will persist through Saturday night. Saturday: Expect scattered showers and thunderstorms at daybreak with the surface cold front just entering the area from the west. Our severe convective potential will be tied to how much instability we can regain ahead of the cold front as it looks to reach the coast by early afternoon. There will be ample deep shear /40-50kt at H5/ to support severe convection. Clearly the best chance for instability to rebound sufficiently to support new convective activity will be over southern NH and far southwestern ME. CAMs support a glancing blow along the NH/MA border with more robust activity to the south and thus the SPC Marginal Risk area looks good. Will continue to highlight this potential in the afternoon Hazardous Weather Outlook...but feel that it is a small window in space and time /11am-3pm/ where severe convection will be possible. While temperatures will be cooler than today...dewpoints will be much higher. Would expect parts of SE NH and SW ME to push into the mid 80s which may allow heat indices to near 90 for a time before drier air returns in the afternoon. Saturday Night: Robust dry advection will push PWATs to 0.5" overnight as surface dewpoints fall back into the 50s and even upper 40s. Temperatures aloft will fall back towards +10C at H8 under modest westerly winds. Thus clear/mostly clear skies are expected with lows falling back into the 50s for the mountains and foothills...with 60s to the south and east.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/...
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Overview... New England sits inbetween an upper level low over Newfoundland and a broad, low amplitude ridge over the central US through most of the extended period. This brings several shortwaves overhead in a broadly positive area of vorticity creating unsettled conditions for the second half of the week. One stronger shortwave brings an area of low pressure on Tuesday with a chance of rain over most areas of Maine and NH. Details... Independence Day: High pressure builds in behind the cold front Sunday into Monday bringing drier air for the later part of the holiday weekend. Mixing will set in both afternoons with a comfortable breeze and highs in the low 70s up north and low 80s in the south. Clouds and showers start moving in Monday evening from the northwest as low pressure approaches for Tuesday. Tuesday Onward: Low pressure starts tracking east across the northern plains at the start of the week, slipping into New England for Tuesday, bringing showers and some possible thunderstorms throughout the day as it passes. The structure of this low is rather unorganized and has been difficult for the models to capture, although a more consistent signal is finally starting to be resolved. Showers will fill in across the CWA over the morning, moving offshore by Wednesday. A broad area of positive vorticity sits overhead for the remainder of the week with unsettled conditions lingering behind the low. Several chances of showers swing through Thursday and Saturday under these unsettled conditions. No significant impacts are expected at this time.
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&& .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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Short Term... Summary: Clouds will thicken and lower overnight as showers and embedded thunderstorms arrive ahead of a cold front. This cold front will push through the region on Saturday with showers and thunderstorms coming to an end and improving conditions arriving Saturday night. Restrictions: VFR conditions persist through 08Z Saturday. Beyond this...a period of MVFR CIGS and possible MVFR VSBYS is expected as an area of showers and embedded thunderstorms moves through the area. Improvement to VFR is expected during the mid to late morning Saturday with VFR Saturday afternoon and Saturday night. Winds: Southwest winds 12g20kts continue into this evening before diminishing to less than 10kts overnight. Southwest winds will gradually veer westerly during the day on Saturday as the cold front moves through...increasing to 10g18kts. Westerly winds diminish to less than 5kts Saturday night. LLWS: 1.5kft winds increase to 30-35kts tonight along the coast...with LLWS possible. Greatest threat is PWM-RKD and have included it in this TAF package. Will have to watch for possible need at PSM-AUG. Shear is weaker to the north and west of this. Lightning: Isolated/scattered thunderstorm activity is expected after midnight tonight with activity south of the mountains persisting into the morning on Saturday. A few strong to possibly severe storms are possible late Saturday morning through mid Saturday afternoon CON-MHT-PSM. Long Term...VFR conditions prevail through Monday under high pressure until ceilings thicken and lower Monday night into Tuesday as low pressure brings SHRA to most terminals Tuesday. Conditions should return to VFR on Wednesday. Unsettled conditions could bring a few chances of lower ceilings and MVFR through the end of the week.
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&& .MARINE...
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Short Term...SCAs for winds and seas will continue into Saturday given brisk southwesterly flow ahead of an approaching cold front. This cold front will pass through the waters Saturday afternoon with winds and waves subsiding into Saturday night. Long Term...Calm winds and seas are expected through next week with a chance of showers on Tuesday. Seas will remain around 2-3 ft.
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&& .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 11 AM EDT Saturday for ANZ150>154. && $$ SYNOPSIS...Arnott NEAR TERM...Arnott SHORT TERM...Arnott LONG TERM...Thunberg AVIATION...Arnott/Thunberg MARINE...Arnott/Thunberg

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