Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 252327 AAB AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 727 PM EDT Mon Sep 25 2017 .SYNOPSIS... High pressure will hold over the region tonight and will shift east on Tuesday. A cold front will approach from the northwest on Wednesday and will cross the region Wednesday night. Weak high pressure will build over the region on Thursday. A secondary cold front will drop south through the region on Friday. High pressure will build in from the west over the weekend. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 727 PM Update... Minor changes this update for current temperature and dew point readings. 505 PM Update... Adjusted PoPs for this afternoon`s showers across the higher terrain. Expect these to dissipate in the next couple of hours. No lightning is noted with these showers. Adjusted fog for the overnight and morning hours. A climate section was added below with Manchester, Concord, and Augusta all breaking their high temperature records today. Previous discussion... High pressure will hold over the region overnight. Expect diurnal clouds and showers over the mountains to gradually clear with the loss of heating this evening. High tds will result in more dense valley fog overnight and may also affect coastal areas. Lows overnight will will range from the mid 50s to mid 60s. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... Unseasonably warm weather will continue on Tuesday as high pressure slides east. Will likely see another round of showers and possibly a few isolated thunderstorms....mainly over the mountains and higher terrain. Highs will generally reach the mid to upper 80s in inland locations. Once again a sea breeze will cap temps in the mid 70s to near 80 along the coast. Another warm and muggy night on tap for Tuesday night. Expect any lingering evening showers to clear. More dense fog will be likely in valley locations. Lows overnight will range from the upper 50s to mid 60s. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... The more active part of the extended is certainly the beginning. We will see a continuation of the early fall heat Wed. Model guidance continues to show H8 temps in excess of +17C. That is supported by ensembles as well. I have increased temps from the previous forecast...as this supports widespread temps in the mid to upper 80s...if not lower 90s in the typical warm spots. This would be enough to see a few more records fall as well. In addition to the heat...we will have higher dew points too. And this is likely to lead to afternoon MLCAPE in the 500-1000 J/kg range...despite poor lapse rates aloft. With an approaching s/wv trof and associated right entrance region of the H5 jet streak we should see enough lift for at least scattered convection. Forecast shear values on the order of 40 to 50 kts will be favorable for storm organization...and SREF guidance is showing an area of favorable conditions for strong to severe storms in the region. The main question is timing at this point...and whether or not storms can form and maintain before loss of daytime heating. For now I have not added enhanced wording to the grids...but that may be necessary with later shifts. After the cold front pushes thru the forecast area Thu a high pressure of continental origins settles in. This will bring much cooler and drier wx than recent days. Given how warm it has been though this is forecast to just bring temps back towards normals. With the agreement in model guidance for the weekend and beyond...I have gone with the multi-model consensus for days 4 thru 7. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... Short Term...VFR with areas of IFR/LIFR ceilings and vsby in Morning fog. Long Term...For the most part high pressure will be in control. That means widespread VFR during the day...but valley fog and LIFR conditions especially at LEB/HIE at night. We will have to monitor marine fog/stratus Tue night...as a warm front tries to lift N thru the region. That could bring an extended period of IFR or lower conditions for coastal terminals as well. && .MARINE... Short Term...no flags. Long Term...In general winds look to remain below SCA thresholds thru the end of the week. Increased swell will still remain thanks to Maria however...and a SCA for hazardous seas will likely be necessary for late in the week. && .TIDES/COASTAL FLOODING... Southeast, long period swell will begin to increase from the mid week period through the weekend. This will lead to an increased risk of rip currents. && .CLIMATE... The following 3 sites broke their high temperature records today: Manchester reached 89 degrees at 3:20 PM, breaking the previous record there of 87 in 1891. Concord reached 90 degrees at 3:24 PM, breaking the previous record there of 85 in 2007. Augusta reached 88 degrees at 3:20 PM, breaking the previous record there of 87 in 1891. Portland reached 83 degrees and did NOT break their record of 88 set in 1970. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Hanes SHORT TERM...Sinsabaugh LONG TERM...Legro

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