Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 210252 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1052 PM EDT Sat May 20 2017 .SYNOPSIS... Cool high pressure settles over the area tonight. Low temperatures will tumble into the 30s for most locations...and areas of frost are expected tonight across the mountains and most central areas of Maine and New Hampshire. High pressure slides east on Sunday...but gives us plenty of sun. Low pressure will move in from the west on Monday bringing cool weather and some rain. Another low pressure system may affect the region midweek. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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10pm update... Temperatures are dropping into the 40s and are on track to reach freezing in a few hours as the winds continue to calm and skies remain clear. 6pm update... Very quiet evening across northern New England without even a cloud through Maine and NH! Those clear skies will allow for temperatures to drop rapidly overnight tonight as the sun sets. Dewpoints were well into the upper 20s at mid day so there is plenty of potential for radiational cooling. Could see a few degrees colder than currently forecast in the usual valleys but have held off making any changes to see what the sounding and sunset brings. Either way it will be below freezing and headlines are already in place. Prev... High pressure will settle overhead tonight...and allow for a nice radiational cooling set up. H8 temps are forecast to be running on the order of +2 or +3C overnight...increasing slightly towards daybreak. Shaving about 3 to 5 degrees off that continues to support the potential for a freeze in the Nrn zones...and frost into the foothills. It is a dry air mass...so frost may not be widespread.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... On Sun the ridge axis remains overhead...so a sunny but chilly start to the day. Weak pressure gradient will support afternoon sea breezes...so the coast should be cooler than the interior. As the ridge slides Ewd thru the day return flow will begin. It may help keep dew points a couple of degrees warmer than today...though RH values should still be near 30 percent. Late in the day and overnight clouds will begin to move in as a low pressure moves into Canada. A warm front will lift thru...but at this time looks to be mainly dry. I cannot rule out a sprinkle...but expect that the majority of precip will hold off until the cold front approaches. PoP will increase more quickly towards 12z. && .LONG TERM /MONDAY THROUGH SATURDAY/... The deterministic models are in decent agreement on the longwave pattern into the upcoming holiday weekend. We begin the period with a flattening upper ridge across the northeast CONUS. This ridge is quickly kicked offshore in response to digging upstream energy and sharpening upper trough over the Great Lakes southward through the central CONUS and Gulf States. The axis of the deep upper trough will then slide slowly eastward into the eastern CONUS through Friday. ] On 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 cross the area Monday into Tuesday. We`ll see a brief lull in precipitation late Tuesday and Tuesday night as the front retreats 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 a round of steadier rainfall to the region. The timing of this low could prove to be particularly problematic as an astronomical tide near the mllw flood stage Friday night could be high impact with building seas and an onshore wind. The surface low will gradually exit into the maritimes on 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 should bring a dry and seasonable day to the region. && .AVIATION /03Z SUNDAY THROUGH THURSDAY/... Short Term...VFR conditions are expected thru the period. A light pressure gradient Sun should allow for some sea breezes to form and push farther inland than today. Some cloud cover and perhaps a SHRA may push in from the W late Sun...but chances of MVFR...or lower...are not all that high until after 12z. Long Term... Mon - Tue AM...MVFR in -shra with lcl IFR in fog and drizzle. Wed - Thu...MVFR in -ra with lcl IFR in fog and drizzle. && .MARINE... Short Term...With high pressure in control of the waters...winds and seas are expected to remain below SCA thresholds. Long Term... Monday night - Tue...Small Craft conditions are possible outside the bays. Thu...Small Craft conditions are possible outside the bays. && .FIRE WEATHER... Canadian high pressure will continue to build across the region this weekend...with much drier air. Expect a bit higher humidity levels on Sunday than today...followed by a widespread wetting rainfall on Monday. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Freeze Warning from 2 AM to 8 AM EDT Sunday for MEZ007>009-012. Frost Advisory from 2 AM to 8 AM EDT Sunday for MEZ013-014- 018>020. NH...Freeze Warning from 2 AM to 8 AM EDT Sunday for NHZ001-002-004. Frost Advisory from 2 AM to 8 AM EDT Sunday for NHZ003-006-010. MARINE...None.
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&& $$ SYNOPSIS... NEAR TERM...Curtis SHORT TERM...Legro LONG TERM...Schwibs AVIATION...Legro/Schwibs MARINE...Legro/Schwibs FIRE WEATHER...

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