Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 190031 AFDGYX Area Forecast Discussion National Weather Service Gray ME 831 PM EDT Thu May 18 2017 .SYNOPSIS... The ridge of high pressure bringing the very hot temperatures will move east tonight with a trough pushing a cold front through the region on Friday. There could be a few showers and thunderstorms as the front moves through tonight into Friday morning. Expect cooler temperatures behind the front for Friday, with even some frosty conditions possible Friday night and Saturday night. High pressure shifts east on Sunday with a low pressure system crossing the area Monday, bringing rain to northern New England. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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8pm update... added damaging wind wording to thunderstorms for the next few hours across western New Hampshire. Line of thunderstorms currently over VT will move into southwest NH. Expect the storms to fall apart as they move into Maine and the sunsets, although the seabreeze front will need to be watched for additional flare ups. 5pm update... Just a minor tweak for Pop in the CT valley to reflect the increasing shower activity in NY/VT. Have also issued a Beach Hazard Statement for tomorrow in coordination with the Coast Guard. This is intended to highlight the cold water conditions as many paddlers head out on nice sunny days underestimating the risk of hypothermia. This is the first issuance of this product. Hot temperatures this afternoon will cool only a little bit tonight as a moist air mass remains in place and southwesterly winds prevent a good inversion from setting up. Expect lows in the 60s to near 70. Late this evening and into the overnight a few thunderstorms may drift into the area from the west. There are two primary areas where convection will be focused. The first is forming over western Pennsylvania and New York state and will drift eastward and possibly impact portions of southern New Hampshire late this evening. Although there is a small chance that storms could maintain some strong intensity as they arrive, it is more likely that we will only get the remnants of what got triggered earlier as we lose the daytime heating that will be the driver of these storms. The other area is over the Saint Lawrence Valley within an area of broader upper level ascent combined with low level convergence along an approaching cold front. This front will drop southeast into the northern part of the area by morning, and any lingering convection could impact northern areas at that time.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Cold front pushes across the area in the morning, arriving at the coast near midday. Warm air still in place ahead of the front could allow temperatures to warm back into the 80s, but the front moves through too early to provide a significant threat of thunderstorms reforming along it. Expect a northwesterly wind bringing cooler air into the area. This cold advection will combine with downsloping conditions to produce good mixing and relatively gusty winds. Winds could gust to around 30 MPH. Continued cold advection Friday night brings cooler and drier air in from the north. Winds are unlikely to go calm on the first night behind this front, so temperatures should only fall into the 40s to perhaps upper 30s. However, all available MOS guidance is consistently forecasting subfreezing conditions in the northern valleys Friday night, so it is pretty hard to argue with. Perhaps cold advection alone is enough to get temperatures down into the low 30s or upper 20s to the north of the mountains. Expect the frost/freeze threat to remain north of the mountains Friday night. && .LONG TERM /SATURDAY THROUGH THURSDAY/... High pressure will be in control of the region to start the extended. Fairly deep mixing is still forecast Sat...but with cooler mid level temps we should stay in the 60s for highs. Some cooler dew points are possible with that deep mixing...especially if we can get some RH values will be on the low side. Sat night ridge axis settles overhead. H8 temps around +3 to +5C point towards min temps possibly falling into the low to mid 30s. Drier air mass may preclude much frost...but temps will certainly be chilly for some areas that have officially started the frost/freeze program. We will need to monitor for potential headlines. Upper low lifts into the Upper Midwest and pushes a cold front Ewd. S/wv trof is forecast to shear out into Quebec...taking the best forcing for ascent with it. Front will tend to slow down Sun night...though some showers may sneak into the Wrn zones especially late. Front will cross the area Mon...and despite cooler surface temps...the ECMWF indicates some steeper lapse rates are possible aloft. I have maintained some thunder in the grids to cover this. Otherwise mean trof stays around thru midweek and showers cannot be ruled out of the forecast with the lower heights aloft. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... Short Term...Westerly winds diminish a bit tonight. For areas that do lose their gusts, wind shear is possible as a 40KT westerly jet will exist around 2000 FT. Winds shift to the northwest behind a cold front on Friday with winds gusting to around 25 KT behind it. Winds diminish a bit Friday night. Generally expecting VFR conditions through the period, but there could be some MVFR conditions if any showers or thunderstorms manage to sneak into the area from the west and northwest tonight. Long Term...VFR conditions thru the weekend under high pressure...with relatively dry air precluding significant fog. An approaching front late Sun into Mon may bring scattered MVFR SHRA to the area from W to E. Showery wx sticks around into midweek with trof hanging around the area. && .MARINE... Short Term...Southwesterly flow continues today and tonight. Winds do not tend to be very gusty on a warm, southwest flow, so currently thing conditions stay below advisory levels. Winds shift to the northwest behind the front on Friday. Cold advection will promote better mixing, but still expect gusts to remain below 25 KTS expect perhaps near the immediate shoreline. Long Term...High pressure will be in control of the waters thru the weekend. Onshore flow developing early next week may bring seas outside of the bays above 5 ft into Tue. && .FIRE WEATHER... Cooler, drier air moves in from the northwest tomorrow behind a cold front. Relative humidity values could drop as low as 40 percent. Even drier air will be in place Saturday with widespread relative humidity values below 30 percent, but with lighter winds. Better moisture begins returning early next week with widespread rainfall expected Monday. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Beach Hazards Statement from 8 AM EDT Friday through Friday evening for MEZ023-024. NH...Beach Hazards Statement from 8 AM EDT Friday through Friday evening for NHZ014. MARINE...None.
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&& $$ SYNOPSIS... NEAR TERM...Curtis SHORT TERM...Kimble LONG TERM...Legro AVIATION... MARINE... FIRE WEATHER... is the U.S. government's official web portal to all federal, state and local government web resources and services.