Area Forecast Discussion
Issued by NWS Portland, ME

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189 FXUS61 KGYX 220758 AFDGYX Area Forecast Discussion National Weather Service Gray ME 358 AM EDT Mon Jul 22 2024 .SYNOPSIS...
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A stationary front remains south of the area for much of today before lifting northward late today and tonight as a warm front. This front will remain near the area through midweek with waves of low pressure tracking along the front bringing rounds of showers and thunder most days from Tuesday through Friday. High pressure builds in for weekend for a return to dry weather.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A stationary front draped west to east across New England will remain south of the area for much of today with weak high pressure providing mostly fair weather. This front will provide a focus for clouds with more in the way of clouds expected across southern areas closer to the front. Highs will range from the 70s north to mid 80s south with cooler temperatures near the coast as wind will become onshore by mid morning. Latest water vapor imagery shows a short wave diving southeast out of the Canadian Prairies with an upper low over the Midwest. The 00Z model suite suggests the upper low will transition to an open wave today with the short wave helping to carve out a broad trough over the eastern CONUS. This will lead to the stationary front lifting northward this evening and into tonight as a warm front. As this front lifts northward there will be increasing chances for showers and possibly some thunder across southern NH by this evening.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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The warm front will continue to lift northward tonight spreading showers and embedded thunder across the area. PWATs will be on the increase and will approach 1.5 to 1.75 inches by Tuesday morning. These PWATs combined with elevated instability and warm cloud depths greater than 12kft will bring the potential for heavy downpours late tonight and Tuesday morning. The 00Z HREF highlights areas along the mountains to the Lakes Regions of ME and NH with highest probability of heavier downpours although the 3 hour max from the HREF keeps amounts below FFG. The trough developing to the west of New England will help spawn a wave of low pressure that will ride along the front late Tuesday morning. This wave will keeps chances for showers and embedded thunder going into early Tuesday afternoon with PoPs decreasing through the afternoon into the evening. The 00Z HREF mean suggests some areas along the foothills will pick up over an inch of rainfall from tonight into Tuesday afternoon while convective processes will bring the potential for localized heavier amounts. All in all, this looks to be beneficial rainfall as the heaviest amounts are focused along areas where 3 hour FFG is greater than 3 inches. Highs on Tuesday will generally be in the 70s and CAMs suggest Tuesday won`t be a complete washout with much of the area seeing a drying trend during the afternoon.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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Overview: The 500 mb pattern through this period is dominated by a ridge in the western part of the CONUS and a deep trough through the central part. A ridge also remains firmly planted over the Atlantic, leaving the Northeast in the transition zone. This will bring about unsettled weather for the upcoming week as moisture builds under the Atlantic ridge and several upper level disturbances are able to rotate through our area. It is not until the end of the period that this pattern begins to budge and ridging is able to work its way into the Northeast. Impacts: Minimal * PWATs around 1.75 inches during our period of unsettled weather this week may lead to downpours and localized flooding. Current guidance from WPC has portions of our area in a Marginal flash flood risk Thursday. Details: Shower chances continue through Tuesday night, but will remain isolated. Shower activity then becomes more widespread toward daybreak Wednesday as surface low pressure pushes back into the region. Low temperatures will generally be in the 60s with some upper 50s in northern zones. Similar to Tuesday, Wednesday looks to start with some showers as a frontal boundary remains stalled nearby. Shower/thunderstorm activity becomes more widespread late morning/early afternoon, but again becomes more isolated in the late afternoon/early evening as an approaching trough begins to push the stalled boundary out. Mostly cloudy skies once again keep high temperatures capped in the 70s and low temperatures bottoming out in the 60s. Thursday looks like the next chance for a period of significant weather as a warm front primes the atmosphere ahead of an upper level trough and surface cold front. Clouds look to be ample, but the warm air advection and breaks of sun will provide plenty of instability to fuel some potentially strong storms. Forecast soundings are already suggesting CAPE values climbing to near 1000 J/kg with well mixed temperature profiles signaling strong winds being a possible threat. CSU machine learning probablilites are keying in on this as well, highlighting our area with a 5% severe threat. With an upper level jet overhead and PWATS remaining around 1.75 inches, any storm is also likely to contain heavy rain and pose a flooding threat as well. We will be keeping a close eye on how these numbers trend over the coming days. High temperatures will climb into the 80s south of the mountains and upper 70s to the north. Showers and storms taper off heading toward daybreak Friday with low temperatures generally in the 60s. The pattern begins to settle down Friday as the upper level trough and surface cold front push through. Global models seem to agree that enough forcing will remain nearby to keep a slight chance of showers through the day Friday, but a drier airmass will be quickly moving in. The general story for the weekend currently looks to be mostly clear skies with temperatures on a warming trend.
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&& .AVIATION /07Z MONDAY THROUGH FRIDAY/...
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Short Term...VFR likely prevails for much of today with clouds increasing from south to north this afternoon into tonight. Conditions will deteriorate tonight from the MVFR to IFR/LIFR as cigs lower and rain overspreads the area from south to north. Increasing low level moisture will also bring the risk for fog. Flight restrictions will continue through Tuesday morning with some improvement Tuesday afternoon as rain showers become less widespread. Long Term...Ceilings will likely bounce between VFR and MVFR as periods of rain showers move through. Each afternoon will come with the chance for thunderstorms as well. Winds will be generally easterly through Wednesday before shifting southwesterly on Thursday and then northwesterly on Friday. Wind speeds will generally be between 5-10kts.
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&& .MARINE...
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Short Term...Winds and seas remain below SCA thresholds Monday through Tuesday. A front will lift north through the waters later today and tonight with prevailing southerly flow behind the front. There will rounds of showers over the waters tonight along with the potential for fog. Long Term...Conditions hazardous to small craft are not expected through Friday. Seas will be around 2-4ft with wind gusts around 10- 15kts. Winds will be largely onshore through this period. Dense fog is possible at times through Friday.
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&& .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Schroeter SHORT TERM...Schroeter LONG TERM...Baron