Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 191336 AFDGYX Area Forecast Discussion National Weather Service Gray ME 836 AM EST Mon Feb 19 2018 .SYNOPSIS... High pressure will move east of northern New England today. A warm front will move north of the region Tuesday and usher in very warm air for this time of year. A cold front will move through Thursday ushering in cooler air for the end of the week. Another two areas of low pressure will move northeast from the Ohio River Valley next weekend. These systems will bring more unsettled weather and possibly mixed precipitation to portions of Maine and New Hampshire. && .NEAR TERM /THROUGH TONIGHT/...
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Update... Have updated the forecast based on current conditions and latest set of mesoscale models. Depsite a cold start, have adjusted temperatures into the 40s for most areas for high temperatures. Warm air advection and initially, a very dry airmass will allow for readings to climb quickly this morning. Thereafter, clouds will stream in from upstate New York during the afternoon hours. Prev Disc... 6am update... minor adjustment to temperatures which have bottomed out in the single digits in the mountain valleys and will start to rise with the sun. prev disc... A warming pattern begins today as high pressure moves off to our east allowing southerly return flow to set up. Early morning temperatures have dropped into the single digits across the north in sheltered valleys where clear skies have helped the radiational cooling. The February sun will help temperatures rise early and continue warming through the day as the south to southwesterly flow takes hold. High temperatures will climb into the 40s across the area.
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&& .SHORT TERM /TUESDAY/...
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Within the southwesterly flow, a weak short wave current over western New York will move through the ridge late this evening pushing a warm front through the region overnight. This will spread precipitation across the area, in the form of scattered showers. With temperatures both aloft and at the surface well above freezing most of the area will see this as light rain showers. The one region for mixed precipitation will be from Rangeley into Jackman and Central Somerset county. Here the low temperatures will hover at or just below freezing, which may result is some light icing, especially in the mountains above 2000ft. With no significant mixed precipitation expected in the populated valleys will not issue an advisory for this marginal event. Overnight also expect fog to become widespread as warm air moves over the snowpack and begins to saturate. Pockets of dense fog are possible. Tuesday temperatures will continue to climb as 850mb temperatures climb to near record levels (Feb max observed 850mb temp at KGYX is 13C). With the southwesterly flow this sets up a classic spring scenario, wherein New Hampshire and extreme southwest Maine climb into the 60s, while from Portland east through the midcoast onshore flow over 40 degree water keeps temperatures down and fog and low clouds of a marine layer in place. This is reflected well in forecast soundings which show a large surface inversion for KRKD and KPWM and a well mixed region further west through the CT river valley. With the warm advection just setting up, expect highs to remain below record despite reaching 60 across southern New Hampshire. (see records in Long term section below)
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... In the long term unsettled weather and very warm to much cooler with even some mixed precipitation over the weekend. A warm front lifts north of the forecast area Tuesday. This will lead to potential record breaking warmth on Wednesday. Currently forecasting record high temperatures for both Portland and Concord. ***Records for PWM & CON*** TUE WED PWM 61/1994 59/1953 CON 66/1930 64/1872 Expect areas of fog into Wednesday morning with light rain. skies should become partly cloudy Wednesday afternoon allowing the temperatures to soar during the day. Some locations in southern New Hampshire may reach 70 degrees. A cold front wing swing through Thursday morning with some light rain/showers and much cooler. high pressure builds in Thursday afternoon. Models differ a bit on the system for late Friday and Saturday. ECMWF is faster than the GFS. Right now have chance POP for Friday afternoon. Precipitation will likely be snow north and snow to mix central and to mix and then rain southern locations. Forecast gets more muddled Sunday as GFS is bullish on surface low development near the benchmark. For now have snow and mixed precipitation changing to rain coast then back to snow Sunday night. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... Short Term... VFR conditions across the region will come to an end late this evening as increasing clouds and showers move in and a warm front lifts through the region. Warm dewpoints over the snowpack will result in fog overnight dropping conditions to IFR across the region. Tuesday will see VFR return for all but the immediate coastline along the midcoast where IFR in low ceilings remain possible throughout the day. Long Term...IFR/LIFR Tuesday night into Wednesday morning in fog and rain. Conditions improve to VFR Wednesday afternoon. MVFR expected Wednesday night as cold front moves through then VFR Thursday. IFR returns Friday as surface low approaches from the southwest. && .MARINE... Short Term... Increasing southwesterly flow around the departing high pressure will push winds and seas to Small craft criteria and an SCA has been issued for the outer waters, as well as Penobscot bay where the SW flow is favorable for building seas. Long Term...Small Craft Advisory likely for Wednesday as winds increase from the southwest and increasing seas. && .HYDROLOGY... Will be monitoring the rivers over the next few days as the warm weather and some rain may lead to enough runoff to cause ice jam flooding. There are several locations with ice jams in Maine and New Hampshire. Looks like a 72 hour period or longer with temperatures remaining above freezing. It is possible that the warmer weather will weaken the ice so that any rise in river levels will just move the ice harmlessly downriver. QPF should be fairly light with less than a quarter inch expected Monday night through Wednesday in the south and up to an inch in the far north near the Canadian border. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...None. NH...None. MARINE...Small Craft Advisory until 5 AM EST Tuesday for ANZ150>152-154.
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&& $$ JC/CK

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