Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 261118 AAB AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 718 AM EDT Fri May 26 2017 .SYNOPSIS... Low pressure is developing in the Gulf of Maine this morning...bringing an area of heavy rainfall and some thunderstorms to New Hampshire and western Maine. Low pressure will continue northeast into the maritimes through tonight. Weak high pressure will build over the area on Saturday and will shift offshore on Sunday...but at least allow for a window of dry weather. The next system over the eastern Great Lakes will lift north into Quebec Sunday night and will drag a front toward the region on Monday. That front will slowly cross the area late Monday night and Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Update...No major changes to the current forecast based on latest observational trends. LLJ is starting to back as low pressure squeezes under New England. This is slowing its progression and as a result I have updated and raised PoP thru mid morning across much of the forecast area. Deformation precip and precip associated with the low center will also gradually move Nwd into parts of SW NH...but that should slowly weaken thru the morning as best forcing for ascent moves E. I have also upped QPF amounts to better match latest observations and reports. Previous discussion...Well developed warm conveyor belt is moving up the New England coast this morning. A strong Ely LLJ is helping to force an area of heavy rain and embedded thunderstorms. The instability is elevated...so I have not seen much in the way of wind with the storms...but some cloud to ground strikes have been noted in addition to the in cloud flashes. That elevated instability really tapers off to the N...so thunder is only in the grids for another hour or so. PoP may need to be delayed in exiting in future updates...as the low pressure slips under New England and the warm conveyor begins to stall its Nwd movement. It is looking like a fairly widespread 1 to 2 inches of rain...with locally higher amounts Once the LLJ forced precip does finally lift N...the area will be left under the upper low. This will continue showery weather into the afternoon...with only gradually decreasing PoP expected. I also dropped high temps...as little sunshine and lingering precip should help keep us much cooler than normal.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... We remain in cyclonic flow on the backside of departing s/wv trof tonight. That should keep clouds around...though downsloping off the mtns may help to lift those a little bit towards the coast. Significant height rises are not forecast until Sun...so much of the day Sat could be leftover low level moisture and slowly scattering cloud cover. There is no real forcing for showers...but there is also no real forcing to move clouds out quickly. That should keep temps on the cool side of normal. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... The deterministic models are in decent agreement on the longwave pattern through late next week. We begin the period with a weak shortwave ridge traversing the area. This ridge is quickly kicked offshore by Monday in response to a deepening upper trough over the Great Lakes. The upper trough axis will shift gradually eastward and remain across the northeast CONUS through the end of next week. Temperatures this period should average below normal as troughing will dominate across New england. In the dailies...a weak ridge of high pressure will cross the area on Sunday before retreating offshore. Low pressure centered north of the Great Lakes will push a slow-moving occluded front across the region Monday and Tuesday with onshore flow and the advancing baroclinic zone providing a damp start to the new work week. Behind this frontal system...the unsettled weather will continue as an upper trough remains across the northeast and a series of weak cold fronts or surface troughs cross the area. && .AVIATION /11Z FRIDAY THROUGH TUESDAY/... Short Term...IFR/LIFR conditions mainly near the coast this morning...as low pressure moves thru the Gulf of ME. There should be very slow improvement today with daytime heating...but feel that at least MVFR CIGs linger thru the day. Drier air moving in Sat should allow for VFR CIGs finally. For the next couple of hours LLWS is a possibility at RKD...as strong LLJ moves NE up the coast. TSRA will also be possible at PWM...AUG...and RKD as the jet lifts NE. TSRA are generally lasting about an hour with the heaviest RA. Long Term... Mon - Tue...MVFR in shra with lcl IFR in fog and drizzle. && .MARINE... Short Term...SCA conditions will continue thru the afternoon. Winds will diminish early today...with seas taking longer to drop below 5 ft outside of the bays. Long Term... Mon - Tue...Conditions could approach Small Craft outside the bays. && .TIDES/COASTAL FLOODING... The astronomical tide in Portland is 12.0 feet mllw just after midnight tonight. Winds should be off shore by that time...however the high water condition may require a coastal flood statement for a couple hours around the high tide. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ150>154. && $$ NEAR TERM...Legro SHORT TERM...Legro LONG TERM...Schwibs AVIATION...Legro/Schwibs MARINE...Legro/Schwibs TIDES/COASTAL FLOODING...Legro

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