Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 200130 AFDGYX Area Forecast Discussion National Weather Service Gray ME 930 PM EDT Sat May 19 2018 .SYNOPSIS... A warm front will lift north into the region tonight, bringing a period of rain. It will be followed by a cold front on Sunday. High pressure will build in from the west Sunday night and will pass out to sea south of New England Monday. Weak low pressure will pass south of New England on Tuesday. A cold front will drop south through the region Wednesday. Weak low pressure tracks along the international border late Thursday into Friday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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915 pm Update: Have lowered some POPs over the southern half of NH and southwest ME a little sooner due to the radar trends with the back edge of stratiform rains rapidly exiting those areas and moving northeast. Toward morning increased POPs a little to reflect convective activity approaching ahead of the approaching cold front. Otherwise based on latest mesonet data just the usual tweaks in temps/dewpts. With WAA overrunning the cool dome some fog expected to develop and may need to monitored for any areas of dense fog development especially along the coastal areas. 610 pm Update: Rain has overspread NH and southwest Maine so the High POPs forecast is on track. Temps just needed some minor tweaking based on mesonet data, otherwise no other changes needed at this time. Previous Discussion: Broad and weak sfc low passing to our northwest tonight into Sunday, in response to weak wave at 500 MB. WAA induced precip expected this afternoon into tonight, although initially struggling to get going in very dry atmosphere. Should see several hours of light to maybe moderate rain late this afternoon through this evening, with clouds fog and perhaps some drizzle hanging around after midnight into early sunday morning. Once the precip gets going, wet bulb should push many spot in the 50-55 range thru early evening, and temps may drop off a degree or two further, but once the warm front pushes thru, will see temps start to rise in southern and western zones after midnight, with lows mostly in the upper 40s to low 50s. .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... The warm front should have cleared the CWA by mid-morning, sooner in the south, and T/Td will begin to rise. Breaks of sun are possible, especially between the mountains and the coast, although coastal zones, especially mid-coast areas, may hang onto clouds through the morning, otherwise most other areas should be partly sunny by mid-morning. The cold front will cross the CWA from NW-SE from mid morning in the north thru mid afternoon in the south, and this will be accompanied by scattered showers and perhaps a few thunderstorms, as airmass ahead of the front in srn NH, and SW ME gets moist with Tds rising up to near 60 ahead of the front. The showers and tstorms should be offshore by late afternoon, with quick clearing late in the day behind the front. Highs will bi in the upper 60s to low 70s in the mtns and on he coast and in the mids to upper 70s in other parts of the interior. Skies will be mostly clear in the evening, with winds diminishing as well, and the overnight will be clear the light winds. Look for lows in the mid to upper 40s, but only around 40 in the mountains.
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&& .LONG TERM /MONDAY THROUGH SATURDAY/... The deterministic model solutions are in decent agreement on the long wave pattern into the first half of the upcoming holiday weekend. We begin the period with a broad upper trough exiting New England. It`s briefly followed by nearly zonal flow for Tuesday with a weak embedded impulse racing eastward from the Great Lakes. Shortwave energy riding over the top of a building western Canadian ridge with quickly carve out another trough across the Great Lakes and New England for the second half of the work week. This trough shears out by the start of the holiday weekend with ridging in the interim for Saturday. By Sunday...models show troughing across the eastern half of the CONUS with various degrees of phasing between northern and southern stream energy. At this point...it looks like a dry start to the holiday weekend and increasingly unsettled for the second half of the long weekend. In the dailies...a weak moisture starved boundary will drop south across the area on Monday. A shortwave impulse and weak surface reflection will cross the area late Tuesday/early Wednesday with clouds and scattered showers. Another weak moisture starved boundary drops south across the area late Wednesday. High pressure briefly follows for Thursday. Another weak moisture starved boundary drops south across the area Thursday night/early Friday. High pressure and drier air briefly follows late Friday into Saturday. A slow-moving frontal system will gradually move east into the area for the remainder of the holiday weekend with clouds and showers. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/...
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Short Term...IFR-LIFR conditions will continue tonight, with improvement to MVFR during Sun morning and VFR in the afternoon. LLWS will be prevalent over most of the area by later tonight (06z-11z) due to an approaching strong LLJ overrunning the low level inversions in place. This already showing up nicely on 00z RAOBS. There is a chance for TSRA midday thru mid afternoon with the FROPA. VFR at all terminals Sun night, although cannot rule out some vly fog. Long Term... Tue - Thu...Sct MVFR in -shra.
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&& .MARINE... Short Term...Will see increasing SW flow later tonight, which will continue to increase ahead of warm on Sunday. Should see some wind gusts to 25 kts or so on the open waters, and seas to 5-6 ft, so have issued an SCA outside the bays late tonight into Sun evening. The cold front will cross the waters mid-late afternoon, with a brief surge of SCA NW winds thru early evening. Long Term...Winds increase across the waters Monday afternoon but should stay below SCA criteria, as will seas. A brief increase is expected Tuesday and Wednesday as a frontal system passes through the region. Again, winds should stay below criteria. && .FIRE WEATHER... Rain and increasing RH levels will keep things moist through Sunday, and wetting rains are a good bet across most of the area by Sun afternoon. However, drier air will move in behind a cold front, combined with gusty NW winds could produce meteorological red flag conditions on Monday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 10 PM EDT Sunday for ANZ150-152-154. && $$

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