Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 281017 AAA AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 617 AM EDT SAT MAY 28 2016 .SYNOPSIS... A hot day is in store for much of New England high pressure just off the south coast allows for warmth to build north. Some humidity will even build into parts of New Hampshire and make it feel a few degrees warmer than what the thermometer reads. If heat is not your thing...relief is not far away. On Sunday high pressure builds into the Maritimes...and turns winds northeast and off the water. That will send a cold front through eastern parts of the forecast area...dropping temperatures some 15 to 20 degrees from today. That front will hang around the area and provide the focus for increasing showers and thunderstorms into Sunday night and Monday as tropical moisture streams northward into the area. && .NEAR TERM /THROUGH TONIGHT/...
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Update...Minor tweaks to account for latest trends in temps this morning. Previous discussion...Marine fog and stratus will mainly hang tough near and N of PWM this morning...gradually lifting with daytime heating. Then strong ridging aloft will build thru the day...and allow skies to clear. A very warm air mass in place...strong heating...and Wly flow across the interior will mean afternoon highs reaching the low 90s for many. With dewpoints in the 60s...some parts of the lower CT River Valley and ASH-MHT corridor will see heat index values near 95. That will be the main forecast concern today...though there will be a chance for afternoon showers or storms near the coast. Some of the higher res model guidance continues to show QPF developing during peak heating. Given the rising heights...forcing will be weak and anything more than widely scattered convection seems unlikely.
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&& .SHORT TERM /SUNDAY/... Tonight into Sun...a S/WV trof crossing the Maritimes will see high pres build in its wake. As high centers E of Nova Scotia...the pres gradient will reverse across the region and turn winds NEly and onshore. A backdoor cold front is expected to move thru at least Ern zones Sun. Temps could be some 20 degrees cooler vs today. Air mass aloft will remain quite warm to the W of the front could be another very warm day. This may include much of the CT River Valley. At the same time that warmth aloft may strengthen the inversion and make it all the more difficult to rid the marine influence near the coast Sun. Precip chances will revolve around scattered convection in the very warm air mass to the W...and any low level rnfl or drizzle in the marine layer...but overall forcing remains weak again. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... High impact weather: heavy rainfall sunday night into monday may cause localized flash flooding. A broad ridge of high pressure aloft continues to be the main large scale feature over the eastern United States through the next week. This will keep generally mild temperatures in our region under southerly flow. A weak shortwave will help to initiate showers to start the week. Our weather for Sunday and Monday will depend largely on the strength of a tropical system. While Tropical Depression Two will remain well to our south and is expected to move into South Carolina, this tropical moisture will extend into Northern New England. The strong Bermuda high will couple with an approaching front to force a plume of very moist air northwards. Precipitable water will approach 2 inches /near record levels/. Extensive southerly flow around the Bermuda high will also bring warm air allowing the freezing level to rise to around 12,000ft. The tropical moisture and high freezing level will thus set the stage for heavy rainfall. The moist airmass will yield convective showers and thunderstorms. However since storm motion vectors remain very weak /less than 10kts/ there is a risk for localized flash flooding as any storms which form will have ample moisture and not move very fast. The font will push through Monday afternoon allowing for high pressure to build back in from the Ohio River Valley. The ridge remains in place through Tuesday and Wednesday bringing seasonable temperatures with highs in the upper 70s and lows in the 50s. The upper level pattern begins to shift by the end of the week as a trough digs into the great lakes at 500mb. At the surface a low pressure system moves through southern Canada dragging another cold front through the forecast area for the end of the week. && .AVIATION /10Z SATURDAY THROUGH WEDNESDAY/... Short Term...Marine fog/stratus is hanging tough very near the coast from coastal York into Cumberland Counties...advancing farther inland on the Midcoast. This will remain the case thru morning...before gradually lifting with daytime heating. Fog will likely hang just off the coast during the day. Otherwise VFR conditions prevail. This afternoon could see widely scattered SHRA or TSRA develop near the coast...but coverage and location remains uncertain. Long Term... Scattered showers and thunderstorms will impact all terminals on Sunday afternoon into Monday. Brief periods of IFR rain will occur across inland sites. For coastal sites expect ceilings to drop to IFR with fog overnight Sunday into Monday. After Monday afternoon conditions will improve to VFR through the end of the week. && .MARINE... Short Term...Winds and seas are expected to remain below SCA thresholds for the weekend. Cold front pushing SWwd across the waters Sun may allow for a period of seas approaching 5 ft outside of the bays. Long Term... Large scale high pressure will remain over the region keeping winds and seas below small craft criteria. && .FIRE WEATHER... The pattern will remain warmer and humid into early next week. As a result relative humidity values will remain moderate to high. Winds will also remain on the lighter side...with high pressure generally in control. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Legro SHORT TERM...Legro LONG TERM...Curtis AVIATION...Curtis/Legro MARINE...Curtis/Legro FIRE WEATHER...Legro is the U.S. government's official web portal to all federal, state and local government web resources and services.