Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 251536 AAC AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 1136 AM EDT Thu May 25 2017 .SYNOPSIS... A broad area of low pressure from the Ohio Valley through the mid Atlantic coast will slowly lift northeast today through tonight...reaching Cape Cod by Friday morning. Low pressure will continue northeast into the maritimes Friday through Friday night. Weak high pressure will build over the area on Saturday and will shift offshore on Sunday. Weak low pressure over the eastern Great Lakes will lift north into western Quebec Sunday night and will drive a cold front toward the region on Monday. The front will slowly cross the area Late Monday night and Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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11:35 AM Update... Drier air/nose of high pressure continues to intrude over much of the terrain of northern New England and retard the advancement of precipitation into Maine and northern and central NH. Easterly flow has intensified keeping temperatures down in the lower to mid 50s along the coast while northern sections are in the upper 50s to lower 60s. Have increased temperatures over the north just slightly as a result. PoPs were adjusted for later timing in line with latest runs of CAM models and with thinking from previous update (see discussion at 9:07 AM). 9:07 AM Update... Raining now in Keene and Nashua this morning as the first batch of precipitation with this system arrives. Shower activity will still take some time to bring the precip north and east... probably not reaching as far north as the notches of NH or as far east as Portland until at least noon. After this first batch we`ll see a break in the activity more or less...however there will be widely scattered showers still around for the late afternoon and evening hours...mainly over the mountains. Around midnight the stronger short wave associated with this rain event will near and increase precipitation both in intensity and areal coverage. We`ll see some heavy downpours through Friday morning. Have adjusted grids based on these ideas...and followed the HRRR closest of the CAM models for this update. Blended NERFC QPF with orographic adjustments for precip amounts. Also added drizzle tonight mainly in between the two systems as the onshore flow intensifies. 7 AM Update... Rain continues to push north through southern New England early this morning and is generally on track with current forecasts. Expect rain to shift into southern New Hampshire over the next couples of hours and into central New Hampshire and southwest Maine by late morning. Have adjusted temps/tds/rh grids based on latest obs. No other changes planned attm. Previous discussion.... Broad area of low pressure from the Ohio Valley through the mid Atlantic states will lift a warm front northward today. HRRR generally in line with latest radar composite and brings precip into southern New Hampshire and southwest Maine by late morning to early afternoon. This preliminary batch of precip will continue north through the afternoon hours. Only looking for light QPF through this evening with amounts of a quarter inch or less. Onshore flow will quickly pick up this morning with easterly winds becoming gusty by afternoon. High temperatures will only make the mid to upper 50s in coastal and southern interior sections. Farther north...highs will edge into the lower 60s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Just looking for showery precip this evening with some additional light accumulations. Strong vort lobe rotating around upper trough back over the Ohio valley will swing north toward the region after midnight and will bring a shot of moderate to occasionally heavy rain back into the region during the early morning hours and through the day on Friday. Expect rain to taper to showers by Friday evening. Most of the forecast area will see an inch to an inch and a half with locally 2 inches in coastal areas. Long duration of this event should preclude any flooding issues but poor drainage areas may see some brief issues in heavier rainfall Friday. Expect temperatures to show little change Thursday night and Friday with lows Thursday night in the near 50 and Highs on Friday in the 50s to near 60. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Trof will be lifting out Fri night into Sat. Lingering low level moisture should keep clouds and possibly fog around overnight. Clouds will gradually clear out later Sat though as weak s/wv ridging moves across the region. That brief ridge will depart Sun...allowing the next s/wv trof to drive a warm front Nwd thru the Northeast. Models remain consistent with low pressure forming well out to sea along the triple point...which may spare the region another widespread moderate rainfall event. However upper trofing is forecast to remain persistent for the remainder of the work week. Lower heights and cyclonic flow will favor afternoon increases in clouds and chances for showers. Temps will more or less be near normals. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... Short Term...IFR/LIFR ceilings developing today and persisting through Friday. Long Term...Lingering low level moisture may keep some MVFR CIGs around Fri night. Daytime heating into Sat should allow any remaining MVFR conditions to lift. Weak ridging should hold thru Sun...allowing for VFR conditions. The next s/wv trof arrives Mon...and scattered MVFR conditions in SHRA or maybe even a TSRA return. && .MARINE... Short Term...Continuing SCA`s through Friday morning. Long Term...Winds and seas gradually diminish as weak high pressure moves over the waters. Developing Sly flow over the waters by Mon may bring some 5 ft seas outside of the bays. && .TIDES/COASTAL FLOODING... Highest astronomical tides of the year on tap for tonight and Friday night. Have issued a Coastal Flood Advisory for all coastal zones for around the time of high tide tonight. Forecast tide will reach 12 feet in Portland and with a storm surge of .3 to .5 feet will likely see splash-over and flooding of the usual spots around the time of high tide around 1230 am tonight. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT Friday for MEZ023>028. NH...Coastal Flood Advisory from 10 PM this evening to 1 AM EDT Friday for NHZ014. MARINE...Small Craft Advisory until 2 PM EDT Friday for ANZ151-153. Small Craft Advisory until 2 PM EDT Friday for ANZ150-152-154.
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&& $$ NEAR TERM...Hanes SHORT TERM...Sinsabaugh LONG TERM...Legro AVIATION...

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