Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 231738 AAE AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 138 PM EDT Fri Jun 23 2017 .SYNOPSIS... Tropical moisture from the remnants of Tropical Storm Cindy... and an approaching frontal system will result in showers and thunderstorms today and tonight. A series of surface troughs or weak cold fronts will cross the area this weekend into early next week bringing us the chance of showers from time to time...especially in central and northern areas. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1157 AM Update...Forecast in good shape with minor adjustments to lessen area of shower activity as it continues to lift north this hour. Upstream water vapor imagery doesn/t hold much promise for significant forcing through the afternoon...although weak isentropic upglide and increasingly unstable airmass should allow isolated to scattered showers/storms to continue to fire. Clearing trend is beginning and noted this hour that KFIT has already hit 90...with this heat poised to reach into my southern zones over the next few hours. 946 AM Update...Continue to refine PoPs based on latest local and regional radar mosaic. The rain has not been terribly heavy...but it has been persistent. Have also had to drop near term temperatures a good bit given ongoing cloud cover. Breaks to our south and west suggest that we/ll be able to make up for lost time later this morning...with only minor adjustments to afternoon highs at this point. No other significant changes at this time. 810 AM Update...Updated PoPs to reflect widespread rainfall over the northern half of the forecast area...and thus boosted rain chances to categorical in these areas. Expect this to gradually lift north as the mid level flow backs during the day...but north of a LEB-IZG-RKD line...expect shras through the morning. No other changes attm. 715 AM Update... No wholesale changes to the forecast at this time. Showers... some heavy in nature...are already spreading across the forecast area this morning. Expect this to continue based on CAM guidance and current radar. These showers have the potential for very high rainfall rates and overall high QPF given plenty of tropical moisture in the region thanks to Cindy...however the exact location of heavy rainfall is not possible to discern. Adjusted a few parameters including temperatures and dewpoints as well as PoPs. Previous discussion... Clouds are increasing ahead of an approaching low pressure system with southerly flow increasing at the surface. Currently winds are calm but these will increase during the heat of the day with dew points reaching the 60s and temperatures reaching the 70s and 80s. Portions of southern NH and southwest Maine will see upper 80s ahead of a surface front which will arrive late in the day. Precipitation will increase over the higher terrain initially as forcing for ascent arrives and this will spread south and east with time. Thunderstorms are expected with locally heavy rainfall which will tap into moisture from Cindy. Storms will generally be garden variety with substantial forcing arriving so late. Any areas that do get ample insolation may see stronger storms. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Showers continue through the evening and overnight hours with the threat for torrential downpours diminishing after midnight. Drier air does not entrain into the region until Saturday so overnight lows will be on the warm side and in the 60s and even lower 70s. Highs warm into the 70s and 80s Saturday. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Cold front will push offshore by Saturday night, but the broader upper trough will remain over the area for the next several days. This will bring a relatively persistent weather pattern featuring temperatures near normal (highs in the 70s, lows in the 50s to near 60), a light offshore westerly wind, and diurnally-induced showers and occasional thunderstorms each afternoon, diminishing in the evenings. There may be a few stronger waves which rotate through the trough providing a better focus for precipitation, but for the most part precipitation chances are based on afternoon heating beneath the cool trough aloft generating instability and daily scattered showers. Given the light flow pattern, expect a sea breeze most days which will keep the coast a little cooler and limit the precipitation chances there. The axis of the upper trough moves through the region Tuesday into Tuesday night, with a subsident northwest flow behind the trough on Wednesday. This may enhance the shower activity on Tuesday and then cut it off for Wednesday. Surface high pressure over the Southeastern USA shifts east toward the East Coast later in the week, allowing some warmer air to begin spilling into New England late in the week. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... Short Term... Summary: A cold front will move through the region tonight with scattered showers and thunderstorms...becoming more numerous after midnight. Drier air moves into the region on Saturday and continues through Saturday night. Restrictions: VFR conditions should dominate into this evening all sites except KRKD where marine stratus will bring a prolonged period of IFR cigs. Approaching cold front and very moist low level airmass will allow for restrictions to expand...with MVFR/IFR conditions likely after midnight as lingering Cindy moisture streams up ahead of approaching cold front. Expect improvement to VFR on Saturday as cold front moves south of the region. VFR expected Saturday night. Winds: Southerly winds strengthen to 10g15kts for this afternoon...remaining near 10kts tonight before shifting west northwest 12g18kts for the day on Saturday and diminishing to less than 10kts Saturday night. LLWS: 1kft winds to 35kts from the south tonight at RKD above stable marine layer...causing a period of LLWS. Thunder: Can/t completely rule out a stray thunderstorm at any of the terminals through this evening...although the best chances will be at HIE/LEB. Tonight...a few thunderstorms may be embedded with showers that move through the region associated with the cold front. Long Term...A dry west to northwest flow out of Canada will keep conditions VFR this weekend and much of next week. There will be a chance of afternoon showers and possibly a few thunderstorms each day, with the best chance being in the interior. && .MARINE... Short Term...SCA continues for increasing SW winds Friday afternoon into early Saturday morning. Winds will likely peak Saturday evening. Long Term...Cold front moves into the Gulf of Maine Saturday night with a light offshore flow behind it. Winds will be fairly light through the coming week in the absence of any strong pressure systems, with the daily flow being dominated by the sea breeze. && .TIDES/COASTAL FLOODING... Astronomical high tides will continue through the weekend with the possibility of minor flooding particularly with the tide tonight /11:11 pm EDT at Portland/...and potentially again Saturday night. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 8 AM EDT Saturday for ANZ150-152- 154. && $$ SYNOPSIS... NEAR TERM...Arnott SHORT TERM... LONG TERM... AVIATION...Arnott MARINE... TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.