Area Forecast Discussion
Issued by NWS Portland, ME

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670 FXUS61 KGYX 250805 AFDGYX Area Forecast Discussion National Weather Service Gray ME 405 AM EDT Tue Jul 25 2017 .SYNOPSIS... High pressure builds in from the west today...bringing drier weather and clearing. It will shift offshore on Wednesday...allowing some warmer air back into the region. A cold front pushes toward the area on Thursday...with low pressure possibly forming along the front bringing another chance of rain and cooler temperatures. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Low pressure and yesterdays rain will move off into the Gulf of Maine with improving conditions through the day. A secondary area of low pressure remains in upstate New York and scattered showers will continue through the north through the morning. Low clouds will help to keep moisture around through the morning hours, with some patchy fog and drizzle possible through sunrise. Clouds will decrease by afternoon as the low moves out and this will allow temperatures to climb back to near 70. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... High pressure will build into the region tonight. With clear skies and lingering moisture expect valley fog to form throughout the region with dense fog in some of the valleys. Moisture will be the limiting factor in the overnight low temperatures. In the north more dry air will allow temps to fall into the upper 40s while further south will remain in the mid 50s. Wednesday high pressure will remain overhead with clear skies. Temperatures will return to near 80 inland, but cooler on the coast where an afternoon sea breeze will develop. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... High pressure will be shifting E of the region Wed night allowing return flow to set up in its wake. At this time the high pressure is forecast to be expansive enough and have a large enough dry push that any marine fog/stratus should be scoured out of the Gulf of ME by this time. Despite return does not look like higher dew point air mass will have enough residence time over the cooler water to create much of a fog issue ahead of the approaching cold front. Though that could change if the front is delayed. The lead s/wv trof will push attendant front towards the area Thu afternoon. With sufficient heating a strong storm or two is a seasonably strong H3 jet streak crosses overhead. Beyond that there is still considerable uncertainty as to what happens along the trailing portion of the front as the secondary s/wv trof approaches. Model guidance is in strong agreement that convection will fire across parts of the Midwest and track Ewd. The ECMWF remains a bit of a Nrn outlier regarding track of that convection...but after consecutive runs being well N the 25.00z ECMWF has shifted back S. This better matches the GFS and well as its own axis of H8 potential temp advection. As a result the forecast is starting to look mainly dry Fri for Nrn zones...with the best chance for precip to be near the MA border. Beyond Fri...the Ern CONUS will remain in broad trofing...though the Northeast may get into a little s/wv ridging. This will lead to pretty weak forcing and low precip chances thru the weekend...along with no significant heat or cold shots. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... Short Term...Existing MVFR cloud deck will persist through mid morning before conditions return to VFR. Look for IFR fog in the valleys tonight as good rational cooling sets up with high pressure overhear. The high will remain through Wednesday keeping VFR conditions. Long Term...VFR conditions Wed night into early Thu will prevail as high pressure slides offshore. A cold front will approach Thu afternoon with SHRA/TSRA. Any convection could bring MVFR or lower conditions...but confidence is low in timing and placement of cold front due to typical modeling errors at this time range. VFR conditions are expected to return behind the front to start the weekend. && .MARINE... Short Term...High pressure will build over the waters today allowing winds and seas to gradually diminish. Long Term...Sly flow will develop late Wed as high pressure builds offshore. Sustained Sly flow may allow seas on the outer waters to near 5 ft for a time Thu ahead of the approaching cold front. Otherwise winds and seas are expected to remain below SCA thresholds. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ150- 152-154. && $$ NEAR TERM...Curtis SHORT TERM...Curtis LONG TERM...Legro AVIATION...Curtis/Legro MARINE...Curtis/Legro is the U.S. government's official web portal to all federal, state and local government web resources and services.