Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 291224 AFDGYX Area Forecast Discussion National Weather Service Gray ME 824 AM EDT Mon May 29 2017 .SYNOPSIS... Low pressure centered north of the Great Lakes will push an occluded front eastward across New england through Tuesday. This front and an onshore flow will produce cool unsettled weather with showers from time to time along with areas of drizzle and fog. Warmer weather returns for the second half of the work week, but with the chance of showers each day. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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820 AM Update...Have updated the forecast to tighten up pop timing a bit based largely on the time-lagged hrrr ensemble. Much of the morning should be dry with a relatively narrow band of showers moving in during the afternoon and evening hours. Temperatures will remain colder than normal, especially at the coast. 625 AM...Minor ESTF update to ingest the current mesonet into near term grids. Prev Disc... At 06z...a 1000 millibar low was over the upper Great Lakes with associated warm front through the mid atlantic region and a trailing cold front through the Mississippi valley. GOES water vapor showed an upper low vicinity of Lake superior and a shortwave impulse upstream of the forecast area over the upper Mississippi valley racing northeastward. NWS Doppler Radar mosaic showed an area of broken convection stretching from the eastern Great Lakes through the mid Atlantic region. For today...the warm front will lift slowly northward into New England while the shortwave impulse races northeast across the forecast area this afternoon and evening. The band of showers will lift northeast and cross the area during the afternoon and early evening. Otherwise...a mostly cloudy day with onshore flow contributing some patchy drizzle and fog mainly along the coastal plain. Today will be chilly by late May standards with high temperatures limited to the 50s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Shower activity will trail off tonight as the weakening shortwave impulse exits into the maritimes by late evening. We`re left with the persistent onshore flow with widespread stratus and fog along with patchy drizzle for the remainder of the overnight period as the warm front remains hung up to our south and west. Lows tonight will be in the 40s. On Tuesday...the occluding frontal system remains to our south and west with onshore flow continuing. Another weak shortwave impulse will ride northeast and bring another round of more widespread showers during the afternoon. Otherwise...mostly cloudy and cool with some patchy drizzle and fog in the onshore flow. Highs tomorrow will range from the upper 50s to lower 60s. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Overall the global models are in pretty good agreement with the continued blocky pattern through Thursday. It is after this point that the GFS and Euro begin to have very different solutions for the extended mainly concerning how to deal with the East Coast closed low. Looking at long term blocking indices and Hovmoller plots, the blocking pattern should start to break up around day 10 (6/8). Around mid week the large cyclone on the east side of the Rex block which has been affecting our weather will shift east, closer to central Quebec Province but still to our west. The low takes on a negative tilt allowing a series of basal short waves to affect northern New England more directly. With the atmospheric river in place/rich moisture still being pumped north from the tropics, this results in several rounds of showers and thunderstorms this week with at least a couple moderately strong frontal passages. The mountains will be closest to quasi- stationary forcing and this combined with orographic effects will keep clouds and rain showers in the forecast for northern zones for much of the time. The rainiest periods look like Wednesday and again Saturday. There will be chances for more organized convection with thunder given the strength of the cold pool aloft and especially if the timing of frontal passages is favorable for peak heating. In particular Wednesday and perhaps Friday look possible for thunderstorms. Overnight lows this week will generally be in the upper 40s to mid 50s, or slightly above normal. Highs will be in the 60s and 70s with some warmer spots possible over southern and interior sections in westerly flow and also those times when the sun is able to break through the clouds. && .AVIATION /13Z MONDAY THROUGH FRIDAY/... Short Term /through Tuesday/...MVFR in shra with areas of IFR along the coastal plain in drizzle and fog throughout the period. Long Term...Rainy conditions with MVFR or lower ceilings and low visibilities especially overnight and in the morning are expected Wednesday Friday. Fog may be a concern Thursday morning. && .MARINE... Short Term /through Tuesday/...Quiet on the waters with winds and seas below SCA. However...we will see vsby restrictions on the water in showers and fog. Long Term...The next chance of SCA conditions for gusty winds and increasing seas may occur Friday into Saturday as a strong cold front crosses the waters. && .TIDES/COASTAL FLOODING... The astronomical high tide in Portland is 11.1 feet MLLW at 3:08 AM Tuesday. Last night`s tide was about 0.6 feet above predicted levels. With winds and seas virtually unchanged, we may be issuing something for tonight`s tide later today as water conditions may exceed their minimal benchmark levels to produce isolated minor flooding. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$

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