Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 202231 AFDGYX Area Forecast Discussion National Weather Service Gray ME 631 PM EDT Fri Apr 20 2018 .SYNOPSIS... Low pressure centered southeast of Nova Scotia will drag several weak troughs across the area through early Saturday. The circulation around this system will produce cool weather through Saturday with a few rain and snow showers, especially across the higher terrain. By Sunday, high pressure and sunny weather arrives along with the start of a gradual warming trend. By mid week, unsettled weather returns with the approach of our next storm system. && .NEAR TERM /TONIGHT/...
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630PM UPDATE... Still seeing a few convective showers rolling through the northeastern part of the area as the upper low finally pulls away to the northeast. Have received a report of some small hail with the heftier showers, which fits fairly well with the environment today of very low freezing levels with shallow convective showers. Won`t see any significant hail, but this is fairly typical for afternoon showers this time of year. Not really a good way of putting this in the forecast and it won`t last long anyway. With the upper low moving east, we don`t really see any more waves moving around it to enhance shower activity, so the remaining showers should transition to upslope dominant within the broadly subsident flow on the back side of the low tonight. Low temperature forecasts the past few nights have been a bit too cold, so bias was initially to not lower temperatures tonight. However, clouds have already broken up downwind of the mountains, and expect this trend to continue through the night unlike the past several nights. With dewpoints in the upper 20s, we should have a good run at freezing or colder for most locations tonight. ORIGINAL DISCUSSION... The Northeast is currently dominated by a closed upper low which is bringing weak successive waves of energy across the forecast area. Cold air stratus as well as a few widely scattered rain and snow showers are affecting the region today, mainly over the higher terrain and towards the Mid Coast. Mixing as well as a tighter surface pressure gradient has allowed winds to pick up this afternoon. Expect speeds to begin to diminish later tonight before increasing once again Saturday morning. Additional snow showers and clouds will plague the mountains and foothills overnight and into Saturday morning as more short wave energy moves across the northeast. However, looking at Froude numbers, accumulating snow is more likely for the overnight period right along the Canadian border to 40 miles south or so, as well as the notches.
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&& .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... Cyclonic flow will continue to wrap up and shift slowly northeast on Saturday, with flow becoming unblocked. This indicates that widely scattered snow flurries over the mountains are more likely during the day Saturday as opposed to accumulating snow. Temperatures on Saturday will be similar to today with perhaps a few warmer spots inland. We`ll see another day of gusty NW winds which will drop off after sunset. && .LONG TERM /SUNDAY THROUGH FRIDAY/...
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A prolonged period of upper level ridging brings mostly sunny skies and high pressure to the region right through the middle of next week. At 500mb, a ridge moves over the eastern portion of North America for the weekend. As we move into next week a cut off low tries to develop through the Southeast, however the ridging continues over the Northeast with little to no precipitation. Temperatures will warm throughout the period with highs getting into the 60s by Tuesday. By Tuesday the cut off low over the southeast may begin to break down, resulting in low pressure tracking up the eastern seaboard with rain moving into northern New England mid week. Onshore flow will drop temperatures along the coast. We`re still talking about day 6, so there is plenty of room for the timing to shift as it often does with cut off patterns however there is enough of a consensus to stick with likely pops for Wednesday into Thursday.
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&& .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Short Term /through Saturday/...VFR with sct MVFR conditions in mountain -SHRA/SHSN. Improving to VFR throughout after 12Z Saturday. As far as LLWS, this shouldn`t be an issue as winds aloft will weaken overnight. Through this evening however, expect gusts into the 20s. Long Term...Sustained VFR right through the middle of next week as high pressure builds over the area. && .MARINE... Short Term /through Saturday/...Gusty westerly flow will persist through the period but should remain just below SCA even outside the bays. Long Term...Quiet on the waters through mid next week as high pressure builds into the region. Low pressure moves up the coast may bring small craft conditions mid next week. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM UPDATE...Kimble SHORT TERM...Hanes LONG TERM...Curtis is the U.S. government's official web portal to all federal, state and local government web resources and services.