Area Forecast Discussion
Issued by NWS Portland, ME

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719 FXUS61 KGYX 231509 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1109 AM EDT Fri Sep 23 2016 .SYNOPSIS... A strong cold front will gradually drop south across the area today accompanied by showers and isolated thunderstorms. This will be our last above normal day as much colder and drier air will flood into the area tonight behind the cold front. Canadian high pressure will arrive tonight, remaining in control of our weather through the weekend and into early next week. We`ll see cool days and cold nights, with a frost possible for northern areas both Saturday and Sunday nights. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1107 AM Update: Only minor changes this hour to increase PoP across Nrn NH as the next band of showers drops S. Convection across Ern NY is still producing intermittent lightning...so I see no reason to drop thunder for Srn zones. 944 AM Update: Primary changes this hour are to better define PoPs associated with northern band of shower activity now entering my far northern zones...with this activity likely to sink south and weaken with time as mid/upper level forcing depart to the north and east. Did reduce temperatures over southern sections a tad based on what will likely be quite limited solar insolation. Am noting a few lightning strikes over eastern Lake Ontario last hour...and while the setup does not favor much thunder...do not yet feel compelled to remove the slight chance mention from the going forecast. 745 AM Update: Have boosted PoPs within band of showers to categorical for the next couple of hours as it sinks south...although rainfall amounts will remain light. Am tracking another band of showers still north of upstate New York closer to the cold front at H8 /surface wind shift has pulled south of this region. This will bring the potential for continued shower activity over northern areas despite the recent drying trend noted in this area on GYX radar imagery. No other significant changes at this time. 632 AM...this ESTF update reflects current radar trends as well as the 10z mesonet. Prev Disc... At 06z...an east-west frontal boundary extended from northern Maine through southern Quebec. A series of weak 1015 millibar waves were rippling eastward along this boundary. NWS Doppler radar mosaic showed a broken band of moderate convection along and to the north of the frontal boundary. For today...Shortwave impulse situated along the Quebec-Ontario border on GOES water vapor imagery will race eastward and drive the surface cold front south across the forecast area. The heaviest QPF of between one-quarter and one- half inch will be confined to northern and mountains sections this morning with amounts trailing off to under one-quarter inch further south and east. Highs will range from the 60s across the mountains and international border to the 70s over the southern half of New Hampshire into extreme southwest Maine.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... For tonight...any lingering showers vicinity of the Massachusetts- New Hampshire border should quickly exit to our south this evening as drier air arrives behind the cold front. There will be some lingering upslope clouds across the mountains...otherwise we`ll become mostly clear tonight. The lingering low clouds in the mountains and some late night valley fog and stratus should preclude any significant frost threat over the mountains and international border area tonight. Lows will range from the upper 30s across the mountains to near 50 along the New Hampshire seacoast. On Saturday...breezy and cool with sunshine mixing with instability clouds by afternoon in the cool cyclonic zone. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... In the long term...a large upper low across eastern Canada will continue to rotate east with time bringing spokes of short wave energy to New England. With surface high pressure in place, this will primarily mean several reinforcing shots of cooler and drier air along with cloud cover. PW values drop to near a quarter inch Sunday, Monday, and Tuesday mornings. Overnight lows will drop into the 30s and 40s during this time with highs generally in the 50s and 60s. Expect areas of frost both Sunday morning and Monday mornings. Will possible need a frost advisory in areas where the growing season continues. After Monday the forecast becomes less clear with timing of a frontal passage differing widely among deterministic models. Spaghetti plots are in some agreement concerning a warm front arriving Tuesday while high pressure pushes offshore. Another sprawling vertically stacked cyclone deepens over the Great Lakes region and pushes the attendant cold front through New England. The Euro seems too fast while the GFS seems too slow and is also generating several surface waves with numerous bullseye precipitation centers. It has been very hard to come across rain lately...and since there is so much doubt have kept PoPs in the long term in the slight chance to chance range at this time. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... Short Term /through Saturday/...VFR with areas of MVFR in -shra and isold -tsra. Improving to VFR throughout aft 23z. Lcl IFR conditions psbl btw 09 and 12z Saturday in valley stratus and fog. NW sfc wind will gust up to 25 kt Sat afternoon. Long Term...VFR Sunday through Monday. Except chance MVFR/IFR in patchy valley fog Sunday night at HIE and LEB. MVFR is possible in Showers Monday night and Tuesday. && .MARINE... Short Term /through Saturday/...winds and seas gradually build today ahead of the cold front with post frontal wind surge providing a period of marginal small craft winds and seas outside the bays tonight. There`ll be a second surge in wind Saturday afternoon in the deepening cold air with marginal small craft conditions continuing. Long Term...Winds and seas should drop below SCA levels late Saturday night. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory from 8 PM this evening to 6 AM EDT Saturday for ANZ150-152-154. && $$ NEAR TERM...Legro

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