Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 200330 AAB AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 1130 PM EDT Sat Aug 19 2017 .SYNOPSIS...
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High pressure will build south of the region Sunday through Monday before sliding to the east on Tuesday. A cold front will move in from the west Tuesday night and will cross the region on Wednesday. High pressure will build in behind the front Wednesday night through Friday.
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&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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1124 PM Update: Going forecast in good shape with only minor tweaks to temperatures...dewpoints and hourly PoPs necessary given current obs and slower arrival of decaying upstream convection now entering western MA. Will maintain thunder mention for now...but MUCAPES are diminishing and expect that this activity will continue to weaken as it heads north and east. Watching fog development...with a few locations having fallen below one mile last hour /PWM-LEW-RKD/. Gradual dry advection overnight will compete with cooling and for this reason don/t expect fog to become widespread and dense...but a few dense patches are possible. Will consider a SPS if VSBY trends in this direction. Update... Have updated the forecast per current observations and trends. Plenty of Cu remain over northern areas where the terrain kick will work with limited instability to produce widely scattered showers and perhaps a stray thunderstorm overnight. This precipitation will be associated with the passage of an upper level trough during the overnight hours. Have also introduced a chance for showers or thunderstorms, mainly after midnight tonight over southern New Hampshire and far southwestern Maine. Latest HRRR depicting convection over eastern New York State surviving the trip through portions of New England. Sufficient CAPE values to trigger a brief shower or storm as the moisture potentially rides through York county Maine by 09Z. Elsewhere, some low level moisture from yesterdays heavy rain will become trapped underneath a developing inversion overnight. This will lead to patchy fog throughout much of the region. Have made minor adjustments to temperature trends, dew points and cloud over over the next few hours. Prev Disc... At 18z...a 1007 millibar low was off the downeast coast with a trailing cold front through the Gulf of Maine. A 1001 millibar low was centered over northern Quebec with a trailing cold front through the eastern Great Lakes. We`re seeing gradual clearing today behind the departing disturbance over the Gulf of Maine. However, heating and the approaching cold front may trigger a brief shower/isolated thunderstorm through early tonight mainly across the higher terrain. Overnight...partly cloudy skies with patchy fog and valley stratus developing in wake of cold front and shortwave impulse sweeping offshore.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... For Sunday...ridging takes hold although we`ll see a few upslope clouds across the higher terrain. It`ll be a warm day with highs ranging from the 70s across the mountains...to lower and mid 80s elsewhere. Partly cloudy Sunday night with some patchy late night fog and lows in the 50s to lower 60s. && .LONG TERM /MONDAY THROUGH FRIDAY/...
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Models remain in fairly good agreement today on extended forecast for next week. High pressure will crest over the region early Monday before shifting offshore south of New England. Return flow will bring warmer and more humid air back into the northeast through the day under mostly sunny skies. Highs on Monday will generally range through the 80s. Summer-like weather will continue Monday night and Tuesday. Looking for partly cloudy skies Monday night with lows in the lower to mid 60s. Tuesday will start off mostly sunny with high clouds on the increase in the afternoon as a cold front approaches from the west. Looking like a hot one with highs in the 80s to lower 90s. May see some convective activity reaching far northwest zones by late in the day but expect a majority of the forecast area to see a dry day. Cold front will push in from the west Tuesday night. Looking for showers and Thunderstorms overnight some of which could be severe with heavy rainfall. Moderate to strong shear will combine with PWAT`s approaching 2 inches to produce possible damaging winds and heavy rainfall. Although timing of the front not ideal... strong dynamics associated with this shortwave should sustain convection well into the evening and overnight. Looking for a very warm and humid night with lows in the 60s to lower 70s. Cold front will slow as it moves through the region early Wednesday but should finally move offshore by Wednesday afternoon. Highs on Wednesday will range from the mid 70s north to the mid 80s south. Skies will be mostly clear Wednesday night as high pressure begins building in from the west. Should see much more comfortable conditions as cooler and drier air shifts into the region on a northwest flow. High pressure will dominate the weather for the rest of the week and into the weekend. Upper trough settling into the northeast will result in A mix of sun and clouds during the days with mostly clear and cool conditions at night. Highs Thursday through Saturday will range through the 70s with lows overnight in the upper 40s to mid 50s.
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&& .AVIATION /04Z SUNDAY THROUGH THURSDAY/... Short term /through 12z Monday/...Lingering MVFR over mid coast Maine will become VFR by early evening. Overnight...areas of MVFR and lcl IFR will redevelop in stratus and fog. Bcmg VFR throughout Sunday morning with lcl IFR psb btw 08 - 12z Mon in valley stratus and fog. Long Term... VFR Monday through Tuesday. Areas of MVFR/IFR ceilings/vsby in showers and thunderstorms Tuesday night. Becoming VFR for Wednesday through Thursday. && .MARINE...
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Short Term /through Sunday Night/...Seas continue to diminish and the small craft advisory for hazardous seas has been dropped. Long Term... SCA`s may be needed Tuesday into Wednesday.
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&& .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM UPDATE...Arnott

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