Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
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835 FXUS61 KGYX 032158 AFDGYX Area Forecast Discussion National Weather Service Gray ME 558 PM EDT Mon Jun 3 2024 .SYNOPSIS... Weak high pressure builds in from the north through Tuesday for mostly fair weather outside of a few afternoon showers both days. Temperatures will run above normal through mid week with afternoon sea breezes bringing cooler conditions to the coast. A trough approaches from the west Wednesday and will linger near New England through the weekend with unsettled conditions. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Update... Isolated showers in the mountains and foothills will continue to diminish as we move through sunset this evening. The latest HRRR has the precipitation ending by around 00Z as well. Have removed the chance for thunder this evening as the cool and stable maritime airmass continue to push into the interior. Otherwise, only minor tweaks to the near term temperature, dew point and wind forecasts. Prev Disc... More instability and a better moisture profile has lead to a pretty robust cumulus field from the foothills northward across western ME and also into northern NH, but dry air aloft has limited precip to only a few light showers thus far. Over the next 2-3 hours, expect coverage of showers to increase somewhat (with perhaps a storm or two) over these areas as more boundaries come together, but with the dry air aloft aloft I kept limited PoPs to 20-30%. Northerly steering flow aloft could bring some of this activity farther south, but at the same time it`s cooler and much more stable to the south where the seabreeze has gone through. Convection diminishes by sunset with dry conditions expected overnight. Skies will range from partly to mostly cloudy with patchy fog developing in some areas. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... High pressure will be overhead to start Tuesday morning but will gradually sink south through the day. The weak pressure gradient will again allow for quick development of the seabreeze, keeping the coast a bit cooler while the interior again warms into the mid 70s- lower 80s, perhaps reaching the mid 80s across western and northern NH. A pocket of dry air aloft will keep most dry, but more instability and the depth of the low-level moisture will be more favorable across western and northern NH for isolated-scattered afternoon showers. Following the diurnal cycle, showers will diminish by sunset or so. Going into Tuesday night, the upper ridge axis will be centered west of the area, and models are showing weak PVA entering northern New England on the eastern periphery of the ridge. With this source of lift and a small amount of elevated instability, additional showers could develop during the course of the night with this looking to be mainly across northern NH. Outside of any precip that develops, sky will be generally partly cloudy with patchy fog possible with lows in the 50s. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Overview: Rain chances improve during the long term. Expansive low pressure will slowly slide east from the Great Lakes, bringing periods of showers. The lows residence time will keep unsettled conditions in the region at least through the weekend. Details: Surface high pressure will be pulling SE off the New England coast Wednesday, with slight boundary draped across many northern New England states. Return flow from the low will enhance onshore component of wind, leading to packing of temperature gradient fairly far inland. Amid the increase in convergence and instability, will see shower chances jump in the afternoon for much of the interior and mountains. The environment does bear some analysis here. Long, skinny CAPE is presented in soundings, with PWAT values progged to surpass the 75th percentile in the region and improving. So, precip efficiency in any showers or storms would be decent...but mid level RH is fleeting with a warm cloud depth that just gets around 8 to 10 kft. Storm motion also looks marginal initially with slow cloud layer winds but speedier up and downshear winds. The concern here is a marginal environment becoming more potent if developed storms interact with a boundary that forms from seabreeze or terrain. We saw this a couple times last year that lead to localized flash flooding. Considering the dry antecedent conditions, this isnt a large concern at this time. But, storm modes in models are starting to resolve single cells that produce over an inch of rain in isolated areas. This seems to be focused across the foothills and mountains of ME and NH, while also including parts of interior ME. Wednesday night, surface instability falls off with some elevated instability remaining. This could prolong some showers into the evening, but coverage should be on the downtrend. Surface dewpoint depression closes across much of the interior overnight. This could result in fog developing for much of the interior. New developing low over the eastern Great Lakes will hoist a warm front into southern New England Thursday morning. This will lead to more synoptic forced rain moving into the region slowly Thursday. While this surface low is expected to pass off the coast, upper low and occluded front to the west will prolong shower chances into the afternoon and evening hours. This system will continue the unsettled pattern for a greater portion of the extended forecast through the weekend. A chance of rain runs into early next week in the forecast, and unfortunately due to the upper low, it will be difficult to provide much more resolution in timing and coverage at range. One hedge would be the chance for showers to increase during the day and afternoon as daytime heating enhances avail instability. The upper low will slowly move northeast through early next week. && .AVIATION /22Z MONDAY THROUGH SATURDAY/... Short Term...VFR the rest of the day with a few showers, mainly away from the coast and closest to HIE and AUG. Should these pass over any terminal, brief VFR restrictions are possible, but these will dissipate by 00Z. For tonight, light onshore flow will lead to the possibility of patchy fog/low stratus and MVFR to IFR restrictions. Conditions return to VFR through Tuesday morning, which will again prevail through the day with coverage of showers again much too low for VCSH in the TAFs. Patchy fog will be possible again Tuesday night. Long Term...SHRA for interior terminals Wednesday, but restrictions should be minimal. Patchy fog may develop overnight, with trend to IFR ceilings is expected through Thursday. Thurs will also feature invading SHRA/RA through the afternoon. With unsettled weather expected through late week and the weekend, restrictions will be likely at times amid fog, showers, and lowered ceilings. && .MARINE... Short Term...Winds and seas continue to remain below SCA levels through Tuesday night. Light east to southeast flow becomes northeasterly tonight and then returns to more southerly Tuesday afternoon with the seabreeze and high pressure sinking south of the Gulf of Maine. High pressure becomes centered just to the southeast of Cape Cod Tuesday night and will result in a southwest wind at or below 10 kt. Patchy fog is possible tonight through Tuesday night. Long Term...Below SCA conditions expected, although with a humid airmass arriving, fog development over the waters is expected from mid week through the weekend. This could reduce visibility at times for portions of the coastal waters. Broad, upper low pressure will slowly track towards the region during this time, lifting north early next week. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR/SHORT TERM...Cannon LONG TERM...Cornwell