Area Forecast Discussion
Issued by NWS Portland, ME

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528 FXUS61 KGYX 211255 AFDGYX Area Forecast Discussion National Weather Service Gray ME 855 AM EDT Mon Aug 21 2017 .SYNOPSIS... High pressure will build to the south of the region through tonight before sliding to the east on Tuesday. A cold front will move across the region Tuesday night and early Wednesday. High pressure and drier air follows the front Wednesday night through Friday. && .NEAR TERM /UNTIL 7 PM THIS EVENING/...
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855 AM...At 12z a ridge of high pressure was draped across New England. Outside of a few high clouds...and a few fair weather cumulus to develop in daytime heating...a mostly sunny day with high temperatures mainly in the 80s. For this ESTF update...I made minor adjustments to near term grids to reflect the current mesonet. Prev Disc... 7am Update: Quiet morning with only some high clouds spilling into the region. Only fog this morning seems to be restricted to the CT River Valley area and will burn off in the next hour or so. Previous Discussion: Patchy early morning fog otherwise mostly sunny conditions again today. Some high clouds may occasionally spill across the upper ridge at times. Temperatures will be warm with highs in the 80s across most areas.
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&& .SHORT TERM /7 PM THIS EVENING THROUGH TUESDAY NIGHT/... High pressure centered to our south will continue to dominate conditions tonight with dry conditions but a slow rise in dewpoints will be noted making for a muggy night as overnight lows remain in the lower to mid 60s. Some patchy fog once again expected after midnight and into Tuesday morning. Tuesday will be a very warm and humid day with clouds on the increase and scattered showers and thunderstorms developing from west to east in the afternoon. Highs will be mostly in the mid to upper 80s and supported by h85 +15C temps. Tuesday night widespread showers and scattered thunderstorms expected. Total qpf amounts should range mostly in the .25-65 inch range by Wed morning. Stayed close to RFCQPF guidance. Models differ some on ending times with EURO slower and NAM/GFS about 3-6 hour sooner. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... A deep but narrow upper low will stretch from the Northwest Passages in Canada southward to the Mid Atlantic region. This is part of a Rex block which will be in the process of mutating. The easterly low will continue to dig into the Northeastern states from the midweek period through the weekend with weak energy aloft. A cold front will be moving offshore Wednesday morning with precipitation coming to an end from west to east. Should be some patchy fog around during the morning hours. WPC`s QPF totals for the next 7 days are less than a half inch everywhere except for the NH and western ME mountains which may see up to an inch. Most of this is attributed to this event. Over the mountains, lingering clouds and a shower or two will continue Thursday before drier air begins to filter in. We should be able to warm up again under downsloping winds with 80s along the coast and mid o upper 70s inland. The higher elevations should warm into the 70s. High pressure will be in control at the surface beginning Thursday and for several days fostering drier and cooler conditions for late this week into early next week. Highs will drop from the 70s and 80s Wednesday to the 60s and 70s which is more in line with normal values for this time of year. Precipitable water values generally drop below 0.60" or less than 50% of the climatological normal during this time so there should be some nights when we will see ample radiational cooling as the high shifts closer overhead. Overnight lows will drop into the 40s and 50s with some chilly mornings in the higher elevations. This will be the first taste of fall for many places. && .AVIATION /13Z MONDAY THROUGH FRIDAY/... Short term /through Monday Night/...VFR...with sct MVFR and LCL IFR btw 08 - 12z this morning in valley fog. LCL IFR conditions again btw 06-12z Tue in valley fog. Late Tue and Tue night conditions lowering to MVFR to IFR in developing showers and scattered thunderstorms ahead of an approaching cold front. Long Term...LIFR to MVFR conditions are forecast for all terminals Wednesday as a cold front brings scattered showers to the region with some heavier rain for the mountains. Showers may linger for HIE and LEB through Thursday morning before drying out along with the rest of the region. Some fog is possible Thursday morning. Otherwise VFR for the remainder of the work week. Westerly winds may initially be gusty on Wednesday before diminishing under high pressure Thursday and Friday. && .MARINE... Short Term /through Monday Night/...Winds and seas are expected to remain below small craft through early Tuesday as surface high pressure builds to our south. By late Tue and Tue night an increasing south to southwest flow ahead of the approaching cold front will allow SCA conditions to develop. Long Term...Seas will remain above small craft criteria through Wednesday morning at least before diminishing. Winds should stay below 25 kts. && .TIDES/COASTAL FLOODING... We`re in the period of high astronomical tides for the month of August. The high tides of potential concern (referencing Portland Harbor where flood stage is 12.0 ft MLLW) are: 1140 PM Monday.... 11.2 ft MLLW 1231 AM Wednesday. 11.1 ft MLLW The Tuesday night high tide (1231 AM Wednesday) could see some splashover as onshore flow and seas increase ahead of an approaching cold front. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory from 8 PM Tuesday to 8 AM EDT Wednesday for ANZ151-153. Small Craft Advisory from 3 PM Tuesday to 8 AM EDT Wednesday for ANZ150-152-154. && $$ ES is the U.S. government's official web portal to all federal, state and local government web resources and services.