Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 201606 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1206 PM EDT Thu Oct 20 2016 .SYNOPSIS... High pressure will exit into the Maritimes today as low pressure developing over the Ohio Valley tracks northeast towards New England by Friday. This system will intensify as it reaches the southern New England coastline Friday night. A cold front pushes through from the west on Saturday as the storm further strengthens and moves through central New England. Cooler weather will arrive on brisk northwest winds for the latter part of the weekend and early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1206 PM...Minor ESTF update to reflect the latest mesonet and satellite trends in near term grids. Prev Disc... 950 13z...1027 millibar high was draped along the coastal plain of eastern New England. The surface high will retreat offshore by afternoon with clouds gradually increasing ahead of the next disturbance over the Ohio valley and eastern Great Lakes. NWS Doppler radar mosaic showed an area of showers and embedded thunderstorms racing northeast towards western New England. This activity and developing onshore flow will bring increasing pops as we head into the afternoon and evening hours. Minor adjustments were made to the near term grids to reflect the current mesonet as well as satellite trends. Given the east to northeast flow off the waters...I`m monitoring the afternoon high tide for any potential splashover issues. Prev disc... 645 am update... High pressure overhead has begun shifting east this morning ahead of an advancing cold front. VAD wind profile shows 25-30 kts at 1 kft. Temperatures and sky cover were the main elements adjusted for this update. Previous discussion... Cirrus was spilling over into northern New England this morning with near zonal flow and the jet stream in the area. At the surface high pressure was centered over the New Hampshire and Maine borders providing for calm to light winds and mostly clear skies. Radiational cooling has helped temperatures drop into the 30s and 40s but likely won`t drop much more with dew points also in a similar range. Valley fog was noted especially near the Connecticut River Valley. This airmass will support highs in the mid 50s to lower 60s today. High pressure shifts offshore by midday allowing low pressure to approach from the SW.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Rain will begin tonight in the west and spread to include all of NH and western Maine after midnight tonight. There are signals for moderate to even heavy rainfall at times with PW values surging ahead of the slow moving frontal system. Overnight lows tonight will drop into the 40s and 50s due to additional cloud cover and winds that will not entirely decouple. On Friday the warm front attempts to lift into the region as an upper level cyclone pivots into the northeast and begins to close off. Depending on where the warm front stalls...we could see some lower 70s over southern NH and SW Maine. Elsewhere readings in the 60s are more likely. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... A digging progressive long wave upper trough approaches New England Friday night and becomes negatively tilted allowing a secondary area of surface low pressure to develop off the mid atlantic coast and then move north along the New England coast. Very high PWATs and strong upward vertical motion will allow the rain to be heavy at times Friday night into early Saturday. Models generally give total QPF in the amounts of 1.5-2.5 inches with some locally higher amounts possible in the higher terrain. It now appears fairly certain some of the tropical moisture from the system off the southeast U.S. will become entrained into the system being the cause for the heavier rainfall. The system becomes a large closed low over northern New England Saturday as it slowly moves northeast and reaches the Canadian maritimes Saturday night. With the large cyclonic flow plenty of clouds and scattered showers will persist into Saturday night with most occurring in the mountains and foothills. Much cooler air moves across the area Saturday night changing some of the showers in the mountains and foothills over to snow showers with some light accumulations over the higher terrain possible. A cold cyclonic flow aloft and at the surface will continue Sunday and into midweek with cool temps and mostly cloudy conditions. The cyclonic flow will continue the scattered rain and snow showers over the mountains and foothills through midweek. Stayed close to superblend guidance for temps and pops. && .AVIATION /16Z THURSDAY THROUGH MONDAY/... Short Term...VFR conditions today through much of today as high pressure moves off to the east. Valley fog will lift this morning which has brought some favored fog spots down to LIFR conditions. Clouds will be increasing from west to east today, eventually bringing MVFR conditions and showers to northern and western areas this evening. Have added some LLWS in the TAFs with latest VAD wind profiles from KGYX indicating 30 kts below 2 kft. Showers will spread to all areas by Friday with some +RA possible at times. Drizzle and fog will be possible closer to the coast Friday as well. Long Term...IFR to LIFR conditions expected Friday night into early Saturday with the expected rain. A cold front pushes east through the area Saturday, allowing for partial clearing conditions to VFR over southern areas while in the mountains and foothills MVFR conditions in scattered showers will persist through much of the weekend and into early next week. && .MARINE... Short Term...An easterly flow develops today, shifting to southeasterly tonight. Although winds may stay below advisory levels, the onshore fetch will allow wave heights to build above 5 FT by tonight. A SCA has been issued beginning tonight through Friday night. Long Term...The prolonged southeast fetch Friday night will allow seas to increase mainly over the outer waters. The system exits to the northeast on Saturday with a trailing cold front in its wake with a west to northwesterly flow behind it which will likely gust above 30 KT at times through the rest of the weekend. && .TIDES/COASTAL FLOODING... The Friday 4 pm astronomical tide in Portland will be 10.6 feet. A southeasterly flow ahead of the system may allow for building storm tides during the day. This will be monitored as we move through the workweek for possible advisory headlines. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory from 11 PM this evening to 8 AM EDT Saturday for ANZ150>154. && $$ ES is the U.S. government's official web portal to all federal, state and local government web resources and services.