Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 220336 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1136 PM EDT Sun May 21 2017 .SYNOPSIS... High pressure continues to slide east tonight...allowing clouds to increase from the west. Low pressure will move in from the west on Monday bringing cool weather and occasional rain. Another low pressure system may affect the region for the middle to latter part of the week. && .NEAR TERM /THROUGH MONDAY/...
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10pm... minor adjustments to increase Pop for incoming showers. 7pm update.. A few showers trying to work their way into Vermont currently but not clear anything is hitting the ground. Out is western New York more widespread showers will move eastward arriving into western NH near morning. prev disc... Ridge of high pressure more or less holds to our E tonight. This will lead to a gradual increase in clouds...but keep the precip mainly at bay until late. I think initial warm frontal showers will fight the dry air...and we will have to wait for the cold front to bring more widespread precip. PoP increases faster after about 06z to account for this.
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&& .SHORT TERM /MONDAY NIGHT THROUGH 6 PM MONDAY/... A bit of a complicated forecast on Mon...and none of it is pretty really. The cold front is forecast to more or less wash out over the area as the best forcing for ascent heads into Canada. But the remnant boundary will provide a focus for scattered showers during the day. Late towards late afternoon and evening a weak wave will form along the front and head into the Gulf of ME. That will refocus periods of rain along the coast. And unfortunately with lots of cloud cover and precip temps will struggle into the 50s. Rainfall will move out Mon night...with temps falling back into the 40s. Some fog is possible with plenty of low level moisture and falling temps. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... The deterministic models remain in decent agreement on the longwave pattern into the upcoming holiday weekend. We begin the period with digging shortwave energy and a sharpening upper trough that eventually covers the eastern half of the CONUS. The axis of the deep upper trough will then slide slowly eastward reaching the Atlantic coastline on Friday. By Saturday...the upper trough will gradually work offshore with ridging arriving in time for the second half of the holiday weekend. Temperatures this period will average near or below normal as the trough brings clouds and unsettled weather for much of the time. In the dailies...a slow moving frontal system will slide offshore Tuesday. We`ll see a brief lull in precipitation late Tuesday and Tuesday night as the front remains just offshore. Another low will ride northeast along this stalled boundary Wednesday into Thursday with a round of steadier rainfall likely. On Friday...another surface low will ride northeast and bring one final round of steadier rainfall to the region. The timing of this surface low could prove to be particularly problematic...as an astronomical tide near the MLLW flood stage will occur Friday night. The surface low will gradually exit into the maritimes by Saturday along with the upper trough. Rising heights and drier air working in from the west should bring improving conditions from west-to-east during the day. By Sunday...a ridge of high pressure may bring a dry and seasonable day to the region. && .AVIATION /04Z MONDAY THROUGH FRIDAY/... Short Term...VFR conditions continue thru most of tonight...as high pressure slowly slides Ewd. As low pressure pushes a front closer to the area by morning...some showers will try and move into the forecast area...especially across NH. They will be fighting a dry air mass...so confidence is low on coverage and restrictions in SHRA. During the day Mon the front will tend to wash out...but MVFR conditions are possible in any heavier SHRA. This will be followed by a weak wave on the front that will bring areas of MVFR or lower to the coastal terminals. Long Term... Tue AM...areas of MVFR in -shra with lcl IFR in fog and drizzle. Wed - Fri...MVFR in -ra with lcl IFR in fog and drizzle. && .MARINE... Short Term...High pressure will remain in control of the waters thru tonight. Winds will remain onshore and below SCA thresholds...but sustained onshore flow thru Mon will build seas to near 5 ft on the outer waters by the end of the period. Long Term... Thu - Fri...Small Craft conditions are possible outside the bays. && .FIRE WEATHER... The ridge of high pressure moves east off the the coast tonight allowing a moist...unstable southwest flow to develop Monday with periods of rain. A return to drier conditions for Tuesday into Wednesday is in store under a weak ridge of high pressure. && .TIDES/COASTAL FLOODING... The highest astronomical tides of the year will be present late this week and into the upcoming holiday weekend. With a tide of 12 ft MLLW in Portland...it will not take much to cause minor flooding on the New Hampshire and Maine coast. With the possibility of weak low pressure affecting the region Wednesday through Friday...we could see some issues with coastal flooding...splashover...and even minor beach erosion. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...None. NH...None. MARINE...None.
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&& $$ SYNOPSIS... NEAR TERM...Curtis SHORT TERM...Legro LONG TERM...Schwibs AVIATION...Legro/Schwibs MARINE...Legro/Schwibs FIRE WEATHER... TIDES/COASTAL FLOODING...

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