Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 171925 AFDGYX Area Forecast Discussion National Weather Service Gray ME 225 PM EST Sat Feb 17 2018 .SYNOPSIS...
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High pressure will quickly exit into the maritimes this evening. Quick moving low pressure will move south and east of New England tonight and early Sunday, bringing a plowable snow...particularly over southern New Hampshire and coastal Maine. As we move into next week...a warming trend is expected with temperatures moving well above normal...especially Tuesday and Wednesday. Expect some rain late Monday into Tuesday and again Wednesday Afternoon.
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&& .NEAR TERM /THROUGH TONIGHT/...
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At 19z a 1030 millibar high was centered near the Bay of Fundy. A weak area of low pressure was over the southeast CONUS while low pressure was over northern Ontario with a trailing cold front through the northern plains states. Clouds are on the increase ahead of these southern and northern stream impulses as the surface high retreats offshore. The southern stream impulse will race east while an associated surface low tracks rapidly east-northeast and just outside the 40N/70W benchmark late tonight. A surface trough will extend northwest into the coastal plain and will act as an additional focus for heavier snowfall. The model trend has been slightly further to the north and west with QPF and snowfall amounts raised a bit over southern New Hampshire and along the coastal plain of Maine. The advisories have been extended further north and east in Maine with a sharp cutoff in QPF and snowfall amounts as you head north and west away from the coast. The steadier snow will spread northeast this evening and taper off in all but our eastern Maine zones by morning.
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&& .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
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Rapid improvement on Sunday as snow exits our eastern Maine zones by mid morning...with downslope and drier air bringing clearing to all but mountain sections where upslope will generate a few lingering clouds and snow showers. Northwest winds will gust up to 25 mph in the wake of the low as it begins to rapidly intensify well offshore. Quiet Sunday night as high pressure builds by to our south. There will be a few late night warm air advection clouds across northern New Hampshire and Maine Sunday night where a few flurries will be possible.
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&& .LONG TERM /MONDAY THROUGH SATURDAY/...
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12Z model suite continues to indicate a large and persistent upper level ridge will develop during the early to midweek period next week along the east coast. This will lead to very warm temperatures during the period. In the dailies, the southwest flow will begin on Monday as warm air advection develops over a large area in the Northeast. The airmass will initially remain relatively dry, so there will only be a low chance for precipitation with this initial batch of moisture. By Monday night, a warm front will become quasi- stationary over northern most sections. This will increase the chance for precipitation, especially in the mountains. Near this dividing line between very warm, humid air and cold temperatures, some freezing rain and sleet is possible. Also, with the increase in low level moisture, expect fog during the overnight period. Increased dew points over the cold snowpack may allow for fog to continue on Tuesday. H8 temperatures reach +10C over southern areas. Depending on the availability of mixing potential, temperatures may quickly rise through the 50s, with 60s over southern areas. There will be a warm start to the day on Wednesday, with H8 temperatures reaching as warm as +14C at H8. This will likely be the warmest day in a long time and perhaps record breaking. Below are the record for Portland and Concord on Tuesday and Wednesday. ***Records for PWM & CON*** TUE WED PWM 61/1994 59/1953 CON 66/1930 64/1872 Cold air advection will begin Wednesday, but not until the afternoon hours. More seasonably cold weather will return for the end of the work week. High pressure will build in from Canada, however readings will still be at or above normal for this time of the year. There remains the potential for another area of low pressure moving up from the southwest next weekend. This system appears to be warm as well with possible mixed precipitation.
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&& .AVIATION /19Z SATURDAY THROUGH THURSDAY/...
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Short Term...VFR deteriorates to MVFR with areas of IFR and local LIFR vcnty of the coast in snow between 01 and 05Z Sunday. Conditions improve to VFR throughout Sunday with some lingering MVFR cigs psb in mtn sections through 22z Sunday. Long Term...VFR to MVFR conditions will continue into early Monday. Areas of IFR/LIFR possible Monday Night into Tuesday night as a warm front approaches and crosses the region resulting in a period of rain and fog. A cold front will sweep through the region later on Wednesday with a period of showers and lower ceilings and visibilities.
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&& .MARINE...
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Short Term...Winds will increase tonight from the south as will seas. On Sunday...northwest winds will generate SCA conditions behind the departing ocean low. A small craft advisory has been issued for all waters except Casco Bay for tonight and Sunday. Long Term...Increased southwesterly winds will allow for SCA thresholds to continue over much of the waters early to mid week next week.
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&& .HYDROLOGY...
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We will have to monitor the rivers closely next week 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.
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&& .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Winter Weather Advisory from 7 PM this evening to 7 AM EST Sunday for MEZ018-023. Winter Weather Advisory from 10 PM this evening to 10 AM EST Sunday for MEZ019-020-024>028. NH...Winter Weather Advisory from 7 PM this evening to 7 AM EST Sunday for NHZ008-010>015. MARINE...Small Craft Advisory from 7 PM this evening to 4 PM EST Sunday for ANZ150>152-154.
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&& $$ NEAR TERM...Schwibs SHORT TERM...Schwibs LONG TERM...Cannon

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