Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 202318 AFDGYX Area Forecast Discussion National Weather Service Gray ME 718 PM EDT Thu Jul 20 2017 .SYNOPSIS... Widely scattered thunderstorms across the region will weaken quickly after sunset tonight. Temperatures will slowly fall back into the 60s for most locations. Friday temperatures tick up a degree or westerly...offshore flow dominates. Temperatures remain warm into the weekend. A low pressure system may bring cooler weather and more potential for rainfall Sunday night into early next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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715 PM...Grids adjusted to account for current convection /mostly winding down/, and to overall lower pops thru the night. Only place which may see a few storms through about 01Z would be the ern zones where some sfc boundaries laid down by previous storms, and better shear is available. Certainly by late evening and overnight should be dry through the CWA. A little drier air moves in behind this system tonight, so Tds may drop off a bit, but still on the humid side, with lows a degree or two lower than last night, probably cooler in the mountains. Previously...Jet streak moving into the Northeast is leading to a broad area of upper divergence over the forecast area this afternoon and into the evening. Given the warm and humid air mass in place at the surface...there is sufficient instability for thunderstorms. Areas of enhanced surface heating of the terrain or sea breeze boundaries...will be the most likely focus for convection. There is also a s/wv trof approaching that may allow convection to persist across the Nrn zones past the loss of daytime heating...but otherwise diurnal cooling will signal the weakening of most storms. Until that time any stronger updraft could produce a strong wind gust or two given effective shear around 35 to 40 kts. Some patchy fog is possible late tonight...especially any areas that picked up a little rainfall today. With the boundary fairly stagnant over the area...low temps will be similar to the past couple of nights.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Fri expect similar temps mid level temps remain fairly consistent. Wly flow may allow for a little extra downslope warming in the favored locations. Another weak wave is forecast to approach the area during the day...and will likely spark another round of widely scattered showers or storms. We also take another step down in humidity...and Fri night should be a little cooler than the previous days. && .LONG TERM /SATURDAY THROUGH THURSDAY/... The models remain in decent agreement on the long wave pattern through the first half of next week. Thereafter, we continue to see big differences emerge regarding the degree of residual troffiness here in New England downstream of the central CONUS ridge. Overall, we`re likely to see both heights and temperatures run below average for much of the extended period. We begin the period with a westerly flow and a broad low amplitude trough here in New England. The weak ridging promised for Sunday in response to digging upstream shortwave energy over the Great Lakes has all but disappeared. The upshot is that the baroclinic zone will stall further north over New England...and any clearing will be confined to the international border area as well as our eastern Maine zones as high pressure over eastern Canada briefly noses into the forecast area. By the start of the new work week, this shortwave energy has carved out a sizable trough across the Great Lakes and northeast CONUS. The trough axis will inch eastward across the region through the first half of next week keeping the region seasonably cool and unsettled. In the dailies...we begin the period with a cold front stretching from our international border area through northern Maine into New Brunswick. This cold front will settle south across the region Saturday and Saturday night with clouds and scattered convection. By Sunday morning...the boundary will be stalled across southern New England with any clearing confined to the international border area and our northern and eastern Maine zones as high pressure briefly noses in.`ll be a mostly cloudy day with the best chance for showers across southern and western New Hampshire. By Sunday night...the frontal zone will ride back north with attendant cloud shield as well as increasing pops and cool unsettled weather in response to evolving upper trough. This cool unsettled weather is expected to linger through the first half of the upcoming work week. && .AVIATION /23Z THURSDAY THROUGH TUESDAY/... Short Term...Widely scattered TSRA will continue into the evening...weakening after sunset. Confidence is too low to include at any of the terminals with significant lead time. Otherwise VFR conditions return tonight. LEB and HIE will be calm enough to see some fog possible after midnight. VFR conditions continue Fri...though an afternoon wave may spark some SHRA or TSRA in the mtns. HIE could see precip...but again confidence is low. Long Term... Sat...Sct MVFR in -shra/-tsra. Sun - Tue...areas of MVFR in -shra/-tsra with lcl IFR in coastal stratus and fog. && .MARINE... Short Term...Winds and seas are expected to remain below SCA thresholds. Long Term... Winds and seas are expected to remain below small craft threshold through the period. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...Cempa/Legro SHORT TERM...Legro LONG TERM...Schwibs AVIATION...Legro/Schwibs MARINE...Legro/Schwibs is the U.S. government's official web portal to all federal, state and local government web resources and services.