Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 262216 AFDGYX Area Forecast Discussion National Weather Service Gray ME 616 PM EDT Sun Mar 26 2017 .SYNOPSIS... A warm front will approach from the southwest tonight, before a weak wave of low pressure forms and passes through the Gulf of Maine Monday. This will provide a round of mixed wintry precipitation Sunday night into Monday. Low pressure moves north of the region on Tuesday and drags a cold front through on Wednesday. High pressure will build in from Canada for the end of the week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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6 pm update: A few areas of very light precipitation upstream will continue to move northeast this evening with most, if not all, of it drying up as it moves into the forecast area due to a very dry air mass over the area in the lower levels. Surface temps are running 35-42 degs attm based on latest mesonet data so increased temps into this evening. Also made adjustments to ptype into the early evening. Based on the warm boundary layer temps and developing low level southeast flow any very light pcpn that does reach the ground could fall as rain. Will be watching to see how surface temps/dewpts react this evening to the low level southeast flow becoming established. Dewpoints already rising and temps may struggle to fall below freezing over southern and coastal areas before they rise later tonight. Any evaporational cooling over southern areas may not offset the waa due to the sely flow. It appears we may need to drop some advisories on a later update over some areas across southern NH and parts of coastal ME. Previous Discussion: Two batches of precipitation will cross our forecast area. First batch over western New England this afternoon will attempt this passage the rest of this afternoon and evening. However, extremely dry Canadian air remains in place in the lower levels of the atmosphere. Much of the echoes shown on radar will dissipate before any precipitation reaches the ground. Nevertheless, latest model suite projecting light precipitation overnight in a warm air advection, cyclonic flow. With such cold and dry air in place, this precipitation will mainly be in the form of light sleet or snow. The most likely area to have freezing rain accretion still appears to be southern New Hampshire. Used a non-diurnal curve for the overnight lows. Temperatures will likely drop with some light precipitation due to evaporation cooling with the first batch. Thereafter, temperatures warm through the night.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Mixed precipitation gradually changes to rain over southern and central areas during the day Monday with mixed precipitation continuing in the north. A weak wave of low pressure will likely form in the Gulf of Maine during the day. This will prevent significant warming as winds become northwest for a period of time. Areas of mixed precipitation likely to continue over the north Monday night. However, much of the dynamics associated with the system will have shifted to the east of the region. Any precipitation should be light. && .LONG TERM /TUESDAY THROUGH SUNDAY/... The models remain in decent agreement on the longwave pattern through late in the work week. Thereafter, timing and strength of individual impulses embedded in fast flow across the northern tier of the CONUS becomes problematic. There is a corresponding decrease in forecaster confidence in sensible weather details after day five. We begin the period with a digging shortwave impulse near the southern tip of Hudson Bay and a weakening impulse over the midwest. By late Wednesday...we`re left with shortwave energy centered over eastern New England. At the surface...low pressure will track from the lower Great Lakes to southern New England by Tuesday night with an area of overrunning rain...and some light wintry mix near the international border...ahead of this disturbance. By early Wednesday...the low and associated frontal system will exit the coast with a brisk northwest flow in its wake along with some upslope clouds and snow showers for the higher terrain. Rising heights arrive for Thursday with a building ridge of high pressure providing a dry but brisk day as gusty northwest winds continue. The ridge will crest overhead Thursday night before retreating offshore on Friday. The next impulse and associated surface low should approach from the midwest by early Saturday. However...models offer a plethora of solutions with this system lending considerable uncertainty to sensible weather details for next weekend. && .AVIATION /22Z SUNDAY THROUGH FRIDAY/... Short Term...Very dry air in place initially in the lower levels. However, moisture will eventually brings ceiling and visibilities down into the IFR category later tonight through Monday. Possible LLWS away from the coast tonight if winds aloft increase sufficiently. Some modest improvement in ceilings/visibilities Monday night. Long Term... Tue...MVFR with areas of IFR in ceilings...-ra and fog. Wed - Thu...Sct MVFR in mtn -shra/-shsn. NW sfc wind gusting to 25 kt. && .MARINE... Short Term...Have raised flags for small craft. Winds increase out of the southeast on Monday. Seas will remain above 5 feet for the outer waters, so SCAs will continue into Monday night. Long Term... Wed - Thu...Small Craft conditions are likely. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Winter Weather Advisory until 5 PM EDT Monday for MEZ007>009- 012>014-018>022. Winter Weather Advisory until 10 AM EDT Monday for MEZ023>028. NH...Winter Weather Advisory until 5 PM EDT Monday for NHZ001>004- 006-009-010. Freezing Rain Advisory until 10 AM EDT Monday for NHZ005-007- 008-011>015. MARINE...Small Craft Advisory from 8 AM to 6 PM EDT Monday for ANZ153. Small Craft Advisory from 8 AM Monday to 6 AM EDT Tuesday for ANZ150>152-154.
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&& $$ Near/Short Term...Marine

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