Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 241124 AFDGYX Area Forecast Discussion National Weather Service Gray ME 724 AM EDT Wed May 24 2017 .SYNOPSIS... High pressure over the region will shift east today. Low pressure over the Ohio Valley will slowly lift northeast tonight through Thursday and will reach the vicinity of Cape Cod by Friday morning. Low pressure will continue northeast into the maritimes Friday through Friday night. Weak high pressure will build over the region on Saturday. Low pressure will approach from the west on Sunday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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11z update... Quick update to to adjust temp/td grids. Cirrus shield associated with low pressure passing offshore will gradually shift east this morning leaving a scattered to broken mid level deck in its wake for most of the day. Radar indicating some light echoes across southern New Hampshire but this is not reaching the ground and expect any showers to remain south of the forecast area today. No other changes planned attm. Previous discussion... Weak high pressure will hold over the region today as low pressure passes well offshore. Much of the day will feature variable high and mid level cloudiness along with filtered sun. A weak sea breeze this afternoon will cap temps in coastal zones in the mid to upper 60s. Farther inland highs will top out in the lower to mid 70s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... High pressure will build in from the northeast overnight. NAM suggesting some ocean stratus developing in increasing onshore flow but other models not showing this moisture getting into the region until Thursday so at this point just looking for variable to partly cloudy skies. Lows will range from the mid 40s north to the lower 50s south. Clouds will be on the increase on Thursday as a warm front over the mid Atlantic coast lifts northward. Will see an increasing chance of showers in southern zones as over-running shifts northward. Expect QPF to be light and spotty during the day. Highs in coastal and southern zones will only reach the upper 50s to near 60. Farther north...highs will top out in the lower to mid 60s. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... On Thu the upper low will round the base of the trof and move into the OH Valley. Models are in good agreement that the occlusion will run out ahead of it and towards the forecast area overnight. It will be battling the departing high pressure...so precip should mainly hold off until after 00z Fri. The trailing s/wv trof will help to redevelop low pressure at the triple point...in the Gulf of ME early Fri. This will likely be the period of heaviest precip for NH and Wrn ME. 06z thru about 18z should be pretty wet...with the dry slot working in after that time. PWAT values should be pushing 200 percent of normal...so rainfall may be heavy at times Fri. Expect generally 1 to 2 inches of rain before it is all said and done. Also of note are the high astronomical tides starting Thu night. With tides right around 12 ft...any amount of surge will likely lead to minor flooding. And Thu night especially should see the best overlap of high water levels and onshore flow. Coastal flood headlines may be necessary for this time period. S/wv ridging moves in for Sat and tries to hold thru Sun. The next trof drops in out of Canada to close out the holiday weekend. The unofficial start of summer does not look very summery...as another occlusion looks to push thru late Sun or early Mon. The follow up wave looks delayed this time...so model forecasts are not suggesting any sort of coastal redevelopment. However with trofing remaining in place over the Ern CONUS...unsettled wx will linger...with any sunshine tending to lead to afternoon clouds and showers. && .AVIATION /11Z WEDNESDAY THROUGH SUNDAY/... Short Term...VFR today through tonight. IFR/LIFR ceilings developing on Thursday in the south. Areas of MVFR ceilings in the north. Long Term...Areas of IFR or lower will persist in RA and onshore flow Fri. There may be pockets of higher CIGs...like at HIE...where downsloping off the mtns may help a little. Significant improvement likely will not occur until Sat...when low pressure begins to pull away. Weak ridging Sat into Sun will allow for VFR conditions to return. && .MARINE... Short Term...SCA`s will likely be needed on Thursday. Long Term...SCA conditions will continue into Fri as coastal storm strengthens in the Gulf of ME. Low pressure will not pull away until Sat...so winds and seas will only gradually diminish into the weekend. && .TIDES/COASTAL FLOODING... Astronomically high tides begin tonight with an 11.5 ft peak forecast overnight. With increasing onshore flow may see some minor splash-over but will let the day shift make the decision on any statements or warnings. Coastal flooding still more likely with higher tides Thursday and Friday nights. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$

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