Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 221454 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1054 AM EDT Sun May 22 2022 .SYNOPSIS... Another hot a humid day is expected today away from the coast before a cold front starts to drop south into the the area. This cold front will bring the threat for severe thunderstorms this afternoon and evening with the main threats being large hail, damaging winds, and torrential downpours. High pressure builds in behind the front Monday bringing fair weather through Wednesday with temperatures closer to normal and much lower humidity levels. A frontal system will approach towards the end of the work week for unsettled conditions possible Thursday and Friday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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10:50AM Update... Mainly minor tweaks to temps based on trends and high res data so far this morning. Also refreshed POPs with some high res guidance. The severe threat remains on track for today. Some stronger storms have already developed along an outflow boundary left from storms last night in Caribou`s forecast area, so we`re already getting signs that conditions are conducive for strong to severe storms this afternoon. Update...Minor changes to reflect latest observational trends. Previous discussion...Convection continues this morning...along the periphery of the EML...riding the CAPE gradient. These storms will mainly affect the Boundary Range thru this morning. Not a lot of CAM guidance handling this particular well...but a gradual weakening is anticipated as it moves northeast. Elsewhere the fog and stratus remain locked in place thru morning. Much like yesterday we will have to scatter out the fog before temps can start to really take off. So once again western ME and adjacent NH will be slow going thru mid to late morning. Based on those trends from yesterday high temps across much of NH are still hot but only low to mid 90s now. I will keep the heat advisory in place despite the fact that heat index values will just touch 95 and likely not get much hotter than that. Dewpoints under this EML are fairly run of the mill humid...and not pushing 70 that would really make heat indices uncomfortable. As the cold front approaches this afternoon those temps in the 90s and dewpoints in the mid to upper 60s will support moderate CAPE...even as mid level lapse rates start to decrease. It looks like two potential triggers for convection this afternoon. This first will be differential heating in the higher terrain. CAM guidance to varying degrees tries to initiate storms off the White and Longfellow Mtns. There will be enough shear to organize storms but messy hodographs suggest clustering is most likely. In addition theta-e differences around 20 to 25K supports the development of cold pools. So at least any early convection should favor damaging winds as the primary hazard. Any discrete updraft may be able to tap the departing EML for some large hail before upscale cell mergers.As the afternoon wears on and the cold front approaches a more broken line of convection should result. This will still favor wind damage as the primary concern...but the approaching upper trof and attendant southwesterly LLJ may elongate low level hodographs just enough to bring an all hazards threat for a narrow time window. It is still most likely that any tornado threat is going come from a brief QLCS-type mesocyclone. That threat is most apparent for northern and western zones...matching HREF and CSU machine learning forecasts well...along with the SPC slight risk. This is where I have severe wording in the forecast...with gusty winds/small hail south and east of there.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Convection will tend to follow a more climatologically favored weakening with the loss of diurnal heating as the EML will have departed to the east by tonight. Winds gradually turn offshore and that should bring an end to the fog threat. Just how long it takes the winds to shift will determine how long fog sticks around the coast...if at all. Much drier air will filter into the region overnight...so while air temps may not be much different for most of the area it will feel more comfortable. Similar story is expected Mon afternoon...with highs topping out in the 60s and 70s. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... High pressure will continue to build in from the west Monday night, cresting over the area Tuesday before shifting to our east Wednesday. This will bring a stretch of mostly dry weather with temperatures near normal away from the coast. Onshore winds will keep coastal areas slightly below normal Tuesday and Wednesday. An upper trough will slide into the Ohio Valley Wednesday night into Thursday with an area of low pressure developing over the Great Lakes. The attendant warm front will lift towards New England Thursday bringing increasing chances for showers. Low pressure will then track northeastward into Quebec with a cold front crossing New England sometime between Friday and Saturday morning. High pressure will bring mostly clear skies and light winds Monday night allowing lows to drop into the 30s north and 40s south. As high pressure slides across northern Maine Tuesday, winds will turn onshore knocking temperatures down near the coast during the afternoon. Highs will generally be in the 60s with low 70s along the CT Valley. High pressure continues to slide east Wednesday with southeast winds turning more southerly. This will allow the interior to warm into the low 70s while coastal areas will be restricted to the 60s with more in the way of clouds than Tuesday. Conditions may turn unsettled Thursday as a warm front approaches New England. Over the past 24 hours there has been a trend for less in the way of showers on Thursday from the warm front, although there continues to be a fair amount of spread amongst ensembles with some members bringing widespread showers during the day Thursday. Going into Friday a cold front will approach from the west. There continues to be some timing differences amongst ensembles in the frontal passage with the FROPA occuring sometime between Friday and Saturday morning. Widespread showers will be likely with the FROPA and continue to stick close to the NBM which brings the highest PoPs Friday afternoon. Cyclonic flow aloft may bring continue chances for showers Saturday, primarily in the mountains, with an overall drying trend through the weekend. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/...
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Short Term...Some fog and low stratus linger around RKD today. The marine stratus may try and work back into coastal zones as TSRA approach from the west...but overall not expecting it to be as widespread as tonight. SHRA/TSRA along the cold front may be strong to severe...with large hail and damaging winds possible. Inland TAF sites are most at risk for stronger convection...including HIE...LEB...MHT...CON...and AUG. VFR conditions return behind the front. Long Term...Mainly VFR Monday night through Wednesday. A warm front approaches Thursday with thickening and lowering cigs bringing potential for MVFR conditions.
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&& .MARINE...
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Short Term... A cold front will sweep away fog and stratus this evening...but bring a chance of showers and thunderstorms. Some of the storm may bring gusty winds to the coastal waters before they move east. Winds and seas are expected to remain below SCA thresholds. Long Term...Winds and seas will remain below SCA thresholds Monday night through Wednesday. Increasing southerly flow Thursday into the Friday may bring marginal SCA winds and seas building to 5 ft.
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&& .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...None. NH...Heat Advisory until 8 PM EDT this evening for NHZ008-011>013- 015. MARINE...None.
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&& $$ SYNOPSIS... NEAR TERM...Clair SHORT TERM...Legro LONG TERM...Schroeter AVIATION... MARINE...

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