Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 250253 AAC AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 1053 PM EDT TUE MAY 24 2016 .SYNOPSIS... Low pressure surface and aloft will drift northward across the region through early tonight. This system will bring unsettled weather with clouds and scattered showers and thunderstorms. This weakening system will exit into the Canadian Maritimes tonight. Warmer weather will return on Wednesday ahead of a cold front. The cold front will bring clouds and a few showers and thunderstorms to the area Wednesday afternoon and evening. A ridge of high pressure will build over the area Wednesday night and will hold over the region on Thursday as a warm front approaches from the west. The warm front will stall over the region Thursday night and Friday and will finally push east of the region on Saturday. A cold front will cross the region Saturday night followed by high pressure and dry air to round out the holiday weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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1050pm update: Have refined cloud cover based on good fog product imagery late this evening...helping to define the western edge of the lower cloud cover over western NH. We continue to have a few flare-ups of showers /and rumbles of thunder/ and have adjusted the forecast as these graze my northwestern border. Noting that K1V4 /St. Johnsbury, VT/ is fogging in at this hour with LEB hinting at the same...feel good about /at least/ patchy fog development west of the primary cloud shield overnight. Temps on track with only minor adjustments here. 855pm update: Minor updates this hour to increase cloud cover...and continue PoPs for a few hours along the NH/VT border west of HIE. Temperatures remain in good shape. Noting gradually decreasing visibilities along the coast...with evening webcams corroborating current fog/drizzle area in the forecast well. 507pm update: Have updated this hour to clear out PoPs to the east of exiting band of showers, with anything to the east of this taking the form of drizzle. Have seen some improvement in sky cover from recent visible satellite imagery and have also tried to capture this trend heading through the evening hours. Temperatures are generally on track. Previous Discussion Below... Upper level trough over Cape Cod continues to slowly migrate off to the north and east. Band of precipitation extends from northern Coos county in New Hampshire south and west across southern Vermont. Instability under the trough will be just enough to keep a mention of showers in the forecast overnight. Onshore flow along the coast has been producing a very low cloud deck along with fog and drizzle. Those conditions should persist until the winds turn around to the west later tonight. Once the winds switch then the drizzle should come to an end. However...it will likely take sunshine tomorrow morning before the fog dissipates.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Upper level trough will finally pull away from the area tomorrow and tomorrow night... leaving a more progressive and zonal upper air pattern in place. A weak frontal boundary tries to nudge south out of Canada and into the mountains of New Hampshire and western Maine tomorrow afternoon. This feature may generate enough instability to get some scattered thunderstorms going...but they should be relatively weak and unorganized. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Warm weather continues Thursday as high pressure builds in further at the surface and aloft. Temperatures should warm quickly in a relatively dry airmass with some clouds remaining over the higher terrain and mostly sunny skies across the coastal plain. A warm front approaches from the SW during the late evening hours...but it will take a while for the atmospheric column to saturate so not expecting anything but sprinkles and scattered showers over NH early on. By the early morning hours Friday we should see more coverage over NH and western Maine. The warm front will lift across northern sections providing a focus for showers and thunderstorms along the boundary with decent instability for areas far enough away from the onshore flow. PW values during the Friday to Saturday time frame jump from 1.4 inches areawide Friday to around 1.7 inches along the coast Saturday as a cold front crosses the region. The cold front will trigger more widespread convection with another chance at thunderstorms Saturday. The cool air regime continues with more air moving in from the Canadian maritimes through early next week. In the upper levels of the atmosphere we will shift to NW flow keeping skies cloudy and a few showers around as weak impulses move SE. High pressure builds in from eastern Canada Sunday with slightly cooler temperatures as cool, dry air filters in. Likewise Monday morning will be a little cool with temperatures primarily in the 40s. Preliminary guidance indicates ridging building in again by midweek with increasing temperatures. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... Short Term... Summary: Low pressure nearly overhead this evening will lift north and east through Wednesday with a cold front nearing the region from the north and west Wednesday evening. Restrictions: Conditions are widely varying at the terminals this evening with IFR/LIFR along the coastal sites...with better conditions as one moves inland. Coastal locations will likely deteriorate some overnight with thickening fog and some drizzle anchoring VLIFR/IFR conditions at these locations. Inland...with ample low level moisture and light winds...any clearing will allow fog to develop with local VLIFR/IFR at sites such as LEB and HIE as well. Conditions will improve dramatically to VFR during the morning hours Wednesday...with the last to see improvement likely being AUG and RKD. A shower/thunderstorm may approach HIE towards the very end of the valid TAF period...but coverage is not expected to be great enough to warrant mention in the TAFs at this range. Winds: Light winds /less than 10kts/ cyclonically rotating around low pressure just south of the region /mostly east and northeasterly at the terminals/ will continue through tonight before becoming increasingly westerly 5-10kts for the day on Wednesday. LLWS: No threats this cycle. Thunder: With shower activity pulling west of the evening...expect little to no threat of thunder overnight through Wednesday morning. Isolated/scattered showers and thunderstorms will likely past just north and east of the terminals Wednesday evening...with low probabilities of activity reaching HIE before 00z Thursday. Long Term...VFR conditions Thursday with rain showers developing across NH and northwestern Maine Friday. MVFR or IFR conditions are most likely across KHIE and KLEB. TSRA is possible. On Saturday more widespread showers and thunderstorms are possible with MVFR or IFR conditions possible at all terminals through the night. && .MARINE... Short Term...No flags expected. Long Term...Winds and seas will remain on the calm end of the spectrum Thursday through next Tuesday. The pressure gradient will increase Friday afternoon causing a few gusts to 20 kts. && .FIRE WEATHER... Thursday will be one of the only dry days of the week. RH values may hover near 30% but winds will be light. We are forecasting all areas to receive rainfall this week albeit light. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...Arnott SHORT TERM...Pohl LONG TERM...Hanes AVIATION...Arnott MARINE... FIRE WEATHER...

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