Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 222103 AAA AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 503 PM EDT Mon May 22 2017 .SYNOPSIS... A weak cold front will push east through the region tonight. High pressure will build over the area on Tuesday and hold over the region through Wednesday. Low pressure will slowly move northeast out of the Ohio Valley Thursday and pass through southern New England on Friday. Low pressure will shift east into the maritimes Friday night. High pressure will build over the area Saturday through Sunday. && .NEAR TERM /UNTIL 8 PM THIS EVENING/...
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5pm Update: Primary update is to boost PoPs to categorical in areas of rain ahead of arriving occluded front. Otherwise... forecast is in very good shape. At 18z...a 1004 millibar low was centered north of the Great Lakes with an occluded front extending southward through the eastern Great Lakes and mid Atlantic region. NWS Doppler radar mosaic showed several areas of showers along and ahead of this frontal boundary and upstream of the forecast area. For tonight...the frontal boundary will slide eastward and exit the coastline towards dawn on Tuesday. We`ll see a few showers ahead of this boundary with lingering low clouds along with patchy drizzle and fog for the balance of the overnight hours.
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&& .SHORT TERM /8 PM THIS EVENING THROUGH 6 PM TUESDAY/... On Tuesday...the front progresses further offshore with partly to mostly sunny skies under weak ridging. Highs will be mainly in the 70s...with a few 60s along the Maine coast as the light synoptic flow turns onshore by afternoon. The weak ridge will hold Tuesday night with partly cloudy skies as we remain sandwiched between an offshore baroclinic zone and a second over Quebec Province. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Weak southwest flow aloft will be overhead by mid week as one large trough dominates much of the eastern and central CONUS. Over eastern Canada another cyclone will be pushing onshore and causing flow between the two systems to buckle and eventually prompt the eastern low to eject northeast. At the surface a series of weak troughs connected by a baroclinic zone will stretch from the Canadian Maritimes towards southern New England and into the Midwest. On Wednesday a coastal storm will be filling and moving northeast offshore which night will keep the possibility of showers in the forecast along the coast. Elsewhere high pressure will be in control and there will be a break in the precipitation through early Thursday morning before the next batch of precipitation arrives moving from SW to NE. Even with a break in the rain, expect cool and damp conditions with fog and possibly some drizzle at times in onshore flow. Widespread rain moves in Thursday in associated with the eastern upper low mentioned above and a surface warm front. This will prompt heavy showers through Friday with both the EPS and GEFS indicating high PWAT air and plenty of forcing for ascent available to wring out over an inch of QPF. While the weekend will not be a total washout there will be scattered showers Saturday as a cold front moves through. Broad low pressure will remain active into next week but the details get particularly hard to decipher past day 5. However, scattered showers and below normal temperatures are a safe bet. && .AVIATION /21Z MONDAY THROUGH SATURDAY/... Short Term /through Tuesday night/...VFR conditions deteriorating to MVFR in -shra then to IFR tonight in fog and drizzle. IFR conditions will improve to VFR early Tuesday morning. Long Term...Deteriorating conditions develop on Thursday in fog and perhaps drizzle ahead of bona fide RA which arrives later that day. IFR/LIFR ceilings/vsby Thursday night and Friday. && .MARINE... Short Term /through Tuesday night/...Winds and seas are expected to remain below small craft through the period. Long Term...SCAs May be needed Thursday night and Friday as seas increase above 5 ft. && .FIRE WEATHER... Cool and wet conditions are expected tonight with some drying likely Tuesday and Wednesday before the next low pressure system brings rain Thursday and Friday. && .TIDES/COASTAL FLOODING... High astronomical tides Thursday night (11.8 ft MLLW forecast for Portland), will combine with onshore flow possibly resulting in minor coastal flooding. Another high tide on Friday night (12.0 ft MLLW forecast) will likely again result in minor coastal flooding although winds may be offshore by that time. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Arnott/Schwibs SHORT TERM...Schwibs LONG TERM...Hanes

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