Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 161425 AAA AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 1025 AM EDT Mon Apr 16 2018 .SYNOPSIS... Mixed precipitation, mainly in the form of freezing rain, rain, and sleet will persist through at least this morning before transitioning to rain this afternoon. As the system moves through New England today, strong gusty winds are expected to develop as well, especially on the coast as well as the western slopes of the White Mountains. A broad area of weakening low pressure will persist over the region Tuesday and will shift east on Wednesday. Another area of low pressure will approach from the west Wednesday night and will move east through the region on Thursday. Low pressure will slowly shift east into the maritimes for the remainder of the period. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Update...The struggle is real...but we are finally seeing ASOS/AWOS locations climb above freezing. Across the interior however...typically favored cold air damming locations are stuck at or below 32. That will continue the freezing rain threat into the there is little mechanism for warming besides weak diurnal heating and latent heat of freezing. I will be trimming remaining winter wx advisories as temps climb above freezing. Otherwise...developing LLJ will ride up and over that cold dome thru this afternoon. Strong isentropic lift will support fairly widespread heavy rainfall. QPF still looking at around 2 inches for much of the localized poor drainage flooding is possible...along with rivers rising mainly to action stage. Previously... Rare mid-April freezing rain event ongoing across much of the forecast area this early Monday morning as overrunning continues above an anomalous SFC cold wedge. So far, most roads are just wet, but the combination of freezing rain and sleet continues to cause slippery travel where road surfaces are a bit colder (like bridges, overpasses, and portions of roadways that do not get much sunlight during the day). Therefore, the winter weather advisory continues until 15z today for most zones. However, we have cancelled the advisory for coastal zones as temperatures have warmed to above freezing. Temperatures are expected to gradually climb today as the low level cold air erodes from the western, eastern, and southern edges. Therefore, we expect a transition to plain rain as the morning progresses. This is a good thing, as the heaviest rainfall is not expected to arrive until early afternoon at most locations. Until then, expect slippery spots to persist. In addition, widely scattered power outages will be possible through early to mid morning as freezing rain accumulates on trees and power lines. Forcing for ascent and PWAT values maximize this afternoon just ahead of eastward-advancing SFC low pressure. Heavy rain is expected to be the result this afternoon into the evening hours which could cause mainly minor flooding. In addition to the maximum in forcing, this afternoon and early evening should feature the strongest portion of the southeasterly LLJ. Based on forecast soundings and model ensemble data, have expanded the wind advisory to all of the Maine coast. Will also keep the advisory up for western NH...but keep in mind this is mainly for favorable downslope locations on easterly flow.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Low pressure pulls away tonight with heaviest rainfall and strongest winds ending this evening. The exception is for far eastern zones where the heaviest precip and strongest winds will linger into the overnight hours. Better weather is in the cards for Tuesday, but plenty of clouds are expected with upper level low pressure overhead. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Closed upper low will continue to meander over northern New England Tuesday night and Wednesday. Expect mostly cloudy skies through the period with scattered rain and snow showers. Lows Tuesday night will be fairly uniform across the region in the lower to mid 30s. Highs on Wednesday will range through the 40s north and lower to mid 50s south. Upper low will drift off to the northeast Wednesday night as another one moves in from the west. After partial clearing during the evening expect increasing clouds in southwest zones after midnight and a chance of rain or snow showers toward daybreak. Lows overnight will range from the upper 20s to mid 30s. Fairly weak area of low pressure will move east through the region on Thursday bringing occasional rain showers through the day and into Thursday evening. Highs on Thursday will range through the 40s to near 50 in the south. Surface low will continue east into the maritimes Thursday night. Persistent cyclonic flow will keep skies mostly cloudy with snow or rain showers likely in the north and scattered showers in the south. Lows will again bottom out in the upper 20s to mid 30s. Upper low will remain parked over the area on Friday producing mostly cloudy skies and scattered showers. Highs will once again range through the 40s to near 50. Persistent upper trough will keep skies mostly cloudy Friday night and Saturday with just a slight chance of showers in northern zones. Lows will range from the mid 20s to mid 30s and highs on Saturday will range from the mid 40s north to the mid 50s south. Cyclonic flow will gradually weaken Saturday night and surface high will build in from the west on Sunday. Looking for diminishing clouds through the period with highs finally getting back to normal with readings in the upper 40s to upper 50s. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... Short Term...IFR/LIFR ceilings/vsby today through tonight. VFR Tuesday through Wednesday with areas of MVFR ceilings. MVFR/IFR ceilings developing THursday...persisting through Thursday night. VFR with areas of MVFR ceilings Friday. && .MARINE... Short Term...Winds gradually increase today...with gale force gusts expected. Winds become more SEly late today...with some gusts approaching 45 kts outside the bays. LLJ crosses the waters tonight...with winds becoming Wly behind the cold front and decreasing. Long Term... No issues expected Tuesday night through Friday. && .HYDROLOGY... A very moist air mass will continue to surge northward ahead of a strong low pressure system in the Great Lakes today. The heaviest precip is expected this afternoon and evening. A large area of 1.5 to 2 inches QPF is expected...especially along and southeast of the higher terrain. The question is mainly how much snow melt we get in the temps are forecast to remain near freezing for most of those areas. Ensemble river guidance does forecast a couple locations in NH going above flood...but not widespread enough threat for a flood watch at this time. More likely there could be ponding of water in poor drainage areas as well as river flows near flood. && .TIDES/COASTAL FLOODING... Beach erosion and splash over still possible for high tides today and tonight...although more likely tonight. Current storm surge forecasts keep tide gauges below flood stage today. With E flow likely creating a storm surge up to or around 1 ft...this could yield some minor flooding across the Seacoast of NH...possibly into York Co tonight. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Winter Weather Advisory until noon EDT today for MEZ018-019. Winter Weather Advisory until 5 PM EDT this afternoon for MEZ007>009-012>014-020>022. Wind Advisory until 2 AM EDT Tuesday for MEZ023>028. NH...Winter Weather Advisory until noon EDT today for NHZ001>003- 005>011-015. Winter Weather Advisory until 5 PM EDT this afternoon for NHZ004. Wind Advisory until 8 PM EDT this evening for NHZ001>003-005- 007-011. MARINE...Gale Warning until midnight EDT tonight for ANZ150>154.
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