Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 291622 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1222 PM EDT SUN MAY 29 2016 .SYNOPSIS... While Saturday may have felt like the dog days of will feel distinctly spring-like behind a southwest moving cold front. Temperatures are going to struggle to climb much higher than morning readings for much of the area. The best chance for a nicer day will be areas well the Connecticut River Valley. Tonight moisture associated with Bonnie begins to stream north...and the chances for rain will increase with it. Rain may even be heavy at times into Memorial Day...especially across southern New Hampshire and coastal Maine. && .NEAR TERM /UNTIL 8 PM THIS EVENING/... 1219 PM...minor ESTF update to incorporate the 16z mesonet into near term grids. PREV DISC... 950 13z a 1008 millibar low was centered over the upper Great Lakes with a warm/stationary front extending southeast through southern New England. To the north of this frontal boundary... easterly flow and marine layer with extensive low cloud was found across the forecast area. With the exception of the upper Connecticut valley...GOES visible imagery should broken to overcast conditions across the forecast area. NWS doppler radar mosaic showed a broken area of convection along and to the north of the 850 millibar warm front and some of this activity will impact northern and mountain sections later this morning and during the afternoon hours today. I made adjustments to near term grids to reflect satellite and radar trends as well as the current mesonet. PREV DISC... Update...Only real change from the previous forecast was to increase PoP over central Somerset County to account for current shower activity. Showers ongoing N of the mid level warm front due to WAA are closer to the forecast area than previously thought and the Jackman area will see likely PoP thru mid morning. Previous discussion...What a difference a day makes. High pres building into the Maritimes has pushed a cold front back to the SW across New England. Behind it stratus and patchy fog continues to spread across the forecast area. The result will be temps some 20 or more degrees colder than yesterday. The air mass to our W remains quite warm...and winds aloft remain SWly to Wly advecting that over the top of the low level marine layer. This will strengthen our inversion today...and make it all the more difficult to break thru. High temps across much of the area will be near current readings if stratus can fill in all the way. Farther W across the CT River Valley may escape the marine influence...and temps should be able to climb well into the 70s. Along this differential heating boundary however a few showers or storms may be possible this afternoon. Again with the lack of a strong upper level forcing mechanism...any convection will be widely scattered. && .SHORT TERM /8 PM THIS EVENING THROUGH 6 PM MONDAY/... Tonight attention turns towards Bonnie. WV satellite imagery already shows moisture from her streaming into parts of Wrn PA and NY. This will continue into New England...first with an increase in clouds...followed by an increase in precip chances. Model forecasts depict PWAT values climbing to near 2 inches by early Mon. Those high PWATs coupled with light steering flow will create a recipe for heavy rnfl. However the threat looks more localized than widespread at this I will be holding off on any sort of flood watch headline. ECWMF EPS favors that threat holding off until Mon...and mainly for Srn zones at that. This is supported by the SREF as well. Looking at individual EPS members shows that only a handful drop heavy rnfl over parts of the forecast area...with the rest mainly light to moderate QPF amounts. All the more reason to keep heavy rnfl wording localized at this point. Another thing to keep an eye on will be if trends continue to keep most of the precip across Srn areas Mon. Thru the mtns could clear out and heat a fairly moist air mass. A strong jet streak is forecast move over the region during the afternoon. This could provide the forcing for ascent and shear necessary for a few organized storms. Have added gusty wind wording to the mtn zones for the afternoon...trying to keep it close the SPC marginal risk forecast. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... A broad ridge of high pressure will remain in place over the forecast area for the week. The high strengthens through Thursday and then shifts eastward allowing a 500mb short wave to push towards our region at the end of the week. The high remains in place and the shortwave will rotate to our north through Quebec. A generally warm and sunny week is in store for Northern New England. On Tuesday highs will get into the 80s as temperatures climb to +11C at 850mb. Northwesterly flow in the wake of Monday nights frontal passage will keep the sea breeze at bay allowing the warmth to extend for all but the immediate coastline. On wednesday the temps aloft cool slightly as the high crests overhead. The weak pressure gradient will allow for a sea breeze to push well inland in the afternoon. With water temperatures still in the 50s this will keep temperatures down in the low 70s for all of the coastal plain of Maine and Rockingham county NH. Further inland Keene and the CT river valley will soar to the 80s under sunny skies. Thursday will remain sunny as dry conditions continue under the surface high. Aloft a wedge of colder air pushes southwestwards out of the Canadian maritimes. 850mb temps drop to +5C with surface high temperatures dropping back into the 70s region wide. Friday the ridge starts to break down as a trough moves into the great lakes. A cold front moves through touching off showers and thunderstorms in the afternoon. && .AVIATION /16Z SUNDAY THROUGH THURSDAY/... Short Term...Marine fog and stratus continues to develop this morning behind backdoor cold front. Hi-res model guidance has had a good handle on trends this morning...with development over Srn NH first...and expanding NEwd from there. Coastal terminals will see IFR CIGS this morning...lifting but remaining MVFR today. Will have to keep an eye on SHRA/TSRA this afternoon on the periphery of the cloud deck...but confidence is too low to include in any TAFs at this time. Clouds are then expected to increase everywhere moisture from Bonnie begins to lift Nwd. Heavy rnfl is possible across Srn NH and coastal ME Mon...with IFR or lower conditions in the heavy precip. Long Term...VFR conditions expected through the week under high pressure. Thunderstorms are possible Friday afternoon. && .MARINE... Short Term...Initial surge from backdoor cold front will bring a few gusts near 25 kts this morning. Otherwise winds and seas are expected to remain below SCA thresholds. Some patchy fog will also be possible on the outer waters today. Long Term... High pressure will keep wind and waves calm through the week. && .FIRE WEATHER... Cool...onshore flow will dominate most of the area today. Relative humidity values will remain moderate to high region-wide. On Mon tropical moisture associated with Bonnie will stream into the area. Showers are likely...with some possibly heavy at times. A wetting rain looks most likely across southern areas. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ ES is the U.S. government's official web portal to all federal, state and local government web resources and services.