Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 051159 AFDGYX Area Forecast Discussion National Weather Service Gray ME 659 AM EST Tue Dec 5 2017 .SYNOPSIS... Rain will move in from west to east today in advance of a cold front. This front will cross the area early on Wednesday, bringing an end to the rain and ushering in colder temperatures. The cold front will linger over the western Atlantic through the weekend with several waves of low pressure moving northeast along it. This could provide a chance of light snow along the coast. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Update... Have updated the grids to reflect current trends. One batch of light precipitation will to exit eastern areas over the next hour. Some, if not most of these echoes were probably not reaching the ground with relatively dry air initially in place over the region. Next batch of precipitation over central New York will reach western portions of the forecast area near the Connecticut River Valley during the mid to late morning hours. With the wet bulbing effect across central and northeastern portions of the forecast area, expect some locations to start as a period of snow and/or sleet. This should be relatively light and mainly confined to the higher terrain. Made adjustments to current temperatures and dew points over the next several hours. Otherwise, very little overall change to the main theme of the forecast. Expect some of the gradient this afternoon and evening will skip over an inversion over some interior sections. Coastal areas and the south facing higher terrain however will have very gusty winds. A wind advisory remains in place for the Midcoast region which is rather exposed to Penobscot Bay. Prev Disc... All models bring precipitation across the forecast area today. Some light rain or snow showers may survive the sublimation process, however there will be some dry air in the atmospheric column over interior and northern sections so the bulk of the precipitation should hold off until later this morning. The wet bulbing effect may allow for some snow and sleet at the onset of the precipitation in a strong warm air advection pattern ahead of the approaching cold front. However, accumulations will be mainly confined to the mountains and on the light side. Atmospheric profiles suggest that there will mainly be only a low chance for pockets of freezing rain today. Temperatures will eventually rise well above freezing in northern areas during the day.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... Winds increase out of the south with the highest wind gusts along the coastline and over the south facing higher terrain. Coordinated with Caribou and will match up with advisories along the Midcoast region where wind gusts will be 45 to 50 mph off Penobscot Bay. It is these eastern areas that will also receive the most rainfall, up to an inch to an inch and a half. Non-diurnal temperature curve continues for tonight with a strong warm air advection pattern continuing until about 09Z. Thereafter, mesoscale models indicates the precipitation will begin to shift east of our forecast area. As the front sweeps offshore Wednesday, some clearing and colder weather will enter the forecast area. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Longwave pattern continues to feature a strongly meridional flow over North America with a large ridge over the West Coast and a deep trough through the central and eastern part of the continent extending all the way to the Gulf Coast. New England will be within the trough, so expect persistent cold air. However, being on the eastern edge of the trough means the cold air will be somewhat moderated by the time it gets here, mostly just a few degrees below normal. It also means we will be near the storm track as ripples within the trough eject northeastward triggering a few waves of low pressure which will bring a threat of snowfall depending on how close they track. Models are still inconsistent and ill-defined when it comes to the details of each of these waves, but the overall concept is consistent. Cold air continues to pour in Wednesday night and Thursday with lows in the 20s and highs in the 30s to low 40s. Continued cold on Friday, generally topping out in the 30s. The first of the waves of low pressure will likely track offshore Friday night, bringing the first chance of snow primarily to coastal areas. Have kept PoPs in the low chance range as there still seems to be a good chance this remains too far offshore to produce anything up here. The next wave arrives with the primary upper trough axis on Sunday. This will bring another chance of snow, but again models are not fully latching on to a precipitation-maker for our area so PoPs remain in the low chance range. Just as the cold trough axis moves east Sunday night, another one will drive south out of Canada to replace it on Monday with a stronger shot of cold air arriving for the early to middle part of next week. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... Short Term...Conditions lowering to IFR and LIFR in many areas with low level Cu overspreading the region. Patchy fog tonight. LLWS may be significant beginning this evening over western areas and spreading east as the wind increases sharply with height. A brief inversion may hold for a short period away from the coast allowing for a continuation of LLWS. Long Term...Cold front pushes through Wednesday morning bringing gusty westerly winds and a return to VFR conditions. MVFR ceilings may linger in the mountains through Thursday as lake moisture streams in from the west. Low pressure moving offshore will bring a chance for IFR conditions and light snow Friday night into Saturday mainly for coastal areas. && .MARINE... Short Term...Gales are in place through tonight and into early Wednesday morning. Expect a few gusts approaching storm force, near 50 knots. Long Term...Westerly flow behind the cold front remains at or near advisory levels through Thursday. Model forecasts are inconsistent on timing and track of low pressure offshore of New England this weekend, so current forecast represents a blend of model guidance and likely under-represents the potential wind speeds. It is possible that advisory level winds could occur again depending on the track of the low pressure areas. && .TIDES/COASTAL FLOODING... Have raised coastal flood advisories for today. Very high astronomical tides will partner with a strengthening southerly winds to place a few locations from Portland and points south over flood stage. Expect minor flooding along and near the wharfs of Portland, minor flooding at Granite Point Road in Biddeford as well as some flooding in the Backbay area of Hampton. Coastal flood advisories may be needed for tonight. Water levels will not be as high, but the GMRI wave runup forecasts and in- house coastal flood nomograms suggest building waves may lead to splash- over and beach erosion. As usual, the ETSS model appears underdone for tonight with a negative surge despite gale force onshore winds. Granted the wind direction is from the south which is not necessarily favorable && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Wind Advisory from 10 PM this evening to 6 AM EST Wednesday for MEZ027-028. Coastal Flood Advisory from 11 AM this morning to 1 PM EST this afternoon for MEZ023. NH...Coastal Flood Advisory from 11 AM this morning to 1 PM EST this afternoon for NHZ014. MARINE...Gale Warning from 5 PM this afternoon to 9 AM EST Wednesday for ANZ150>154. && $$ NEAR/SHORT TERM...Cannon LONG TERM...Kimble is the U.S. government's official web portal to all federal, state and local government web resources and services.