National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Portland, ME

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-- Discussion containing changed information from previous version are highlighted. --168FXUS61 KGYX 250145AFDGYXArea Forecast DiscussionNational Weather Service Gray ME945 PM EDT Mon Jun 24 2024.SYNOPSIS...Showers and thunderstorms will come to an end tonight with theweather turning drier and warmer for Tuesday and Wednesday. Lowpressure will bring another round of showers Wednesday nightwith somewhat cooler and drier air arriving for the remainder ofthe work week.&&.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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940pm Update...Quite a busy evening in the hydro department.Precip efficiency and slow storm motion/training was a goodcombo to produce areas of minor and flash flooding (a few roadwashouts have been reported in Chesterville, ME) this evening.This activity should be subsiding as elevated instability isbeginning to wash out as low pulls to the east. Skies shouldbegin to thin after midnight, which could bring lows in thelower 50s to the mountains. Believe some breeze remains acrossmuch of the coast and interior tonight for temps to stay in theupper 50s.Previous Discussion...500 MB with weak sfc reflection current over the CWA, butslowly track ESE this afternoon and evening. It has been settingoff some nearly stationary convective cells sine this morning,but no signs of lightning yet. Given, they are not very large,they been posing almost no issues, expect for the little clusternear Jay, ME which has put down 1-2 in the last couple hours.They are also line up roughly W-E along a sfc boundary from thecluster in Jay off to the where the Penobscot river meet PenBay. Impacts should be limited but will have to keep an eyeanything that hangs a round the same place too often. Also asthat system shift to the SE expect the chance of showers toshift a little more SE toward the coast this evening. Winds onthe back side will shift N and pick up a bit toward evening, butthese should be diminishing after midnight as well. All showersshould be done by 04-06Z, with clearing from W-E following. Theusual mtn valley may decouple late, which could lead to somefog there, with lows ranging from the low to mid 50s in themtns, to near 60 in srn NH and on the ME coast.
-- End Changed Discussion --&&.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...High pressure builds in with NW flow Tuesday morning with theridge cresting over the CWA in the afternoon. This should allowfor a mainly sunny and warm day with highs mostly 80-85,although a little in some mountain spots and a little warmer inthe more populated corridor of S NH. I think winds slacken offenough in the afternoon that a sea breeze develops, but it willdevelop late and will be limited to the immediate shoreline.&&.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...High Impact Weather Potential: Threat for widespread severe weatheris low through the long term forecast. Late Wednesday...ifapproaching surface cold front arrives earlier than currentlyexpected...there would be a severe thunderstorm threat.--Pattern and Summary--Unblocked pattern with multiple shortwaves embedded within thenorthern stream flow indicates a fairly changeable period of weatherwith strong ensemble guidance agreement on precipitation eventsWednesday night and again this weekend. The timing of these eventswill likely determine what...if any severe weather threat they willpose. Temperatures will be above normal on Wednesday and again aheadof the weekend frontal system...returning to around or just belownormal behind these systems. This overall yields a warmer/wetterthan normal period.--Daily Details--Tuesday Night - Wednesday: Warm front pushes through the regionTuesday night with decent LLJ push followed by weak warm advectionthrough Wednesday as the mid level flow slowly backs ahead of thenext shortwave trough over the Great Lakes. Could see a few showersor a rumble of thunder Tuesday night...with dry and warm conditionsto take back over for the day on Wednesday as T8s edge up slightlyfrom those on Tuesday. Thus...upper 80s to lower 90s are likelysouth of the mountains with more clouds and cooler temperaturesaloft keeping highs near 80 to the north. Surface dewpoints willhave moved upward into the 60s...so it will feel a bit humid...though these values should fall short of pushing heat indices muchabove the actual air temperatures.Wednesday Night: Next northern stream shortwave arrives Wednesdaynight and while the global deterministic/ensemble guidance from theEC and GFS are are in solid agreement that this feature will bring around of showers and possible thunderstorms as a cold front pushesthrough the area /with a wave of low pressure potentially forming onthe front/ the GGEM ensemble as well as today/s 12Z NAM that areflatter with the front largely coming through dry. While this spreadin the ensemble guidance suggests caution going with nearlycategorical PoPs over southern areas as shown in the NBM...feel thatthe pattern overall is one that would support precipitation givenmodest mid level wave and PWATs in the warm sector 1.5-1.75".Thus...will continue forecast messaging of likelies. Timing doesnot favor severe weather potential given a lack of instability...butthe kinematics will be there...so any speeding up of the cold frontcould introduce severe thunderstorm potential. The shortwave doeslook to move through quickly...which limits the overall hydrothreat.Thursday through Saturday: High pressure builds into the regionThursday as low pressure moves into the Canadian maritimes...movingoverhead Friday and then offshore for Saturday. This should providefor a dry end to the week through at least the first half ofSaturday. Temperatures fall back towards seasonal normsThursday...and even a few degrees cooler for Friday with drierCanadian air allowing afternoon dewpoints on Friday to fall into the40s. Temperatures begin to rebound on Saturday ahead of the nextfrontal system.Saturday Night - Sunday: There is rather good ensemble agreement foranother frontal passage late Saturday/Saturday night. Currentexpected timing wouldn/t be conducive to a significant severeweather threat...but residual instability and a rather impressivemoisture plume /PWATs push back above 2"/ indicates keeping an eyeon this period in later forecast for potential hydro issues. Showersmay linger into Sunday with temperatures at or slightly aboveseasonal norms.Monday: High pressure builds back into the region to end theforecast period with another push of Canadian air bringing drier andcooler conditions to end the forecast period.&&.AVIATION /02Z TUESDAY THROUGH SATURDAY/...Short Term...A period of MVFR is expected at most terminalslate this afternoon and this evening as weak sfc boundary movethrough and shifts winds to the N. These should break up shortlyafter midnight but before daybreak. Valley fog is possible atpossible at both KHIE/KLEB, although it will depend on howquickly each of those clear out. Vfr is expected on Tuesday.Long Term...VFR Tuesday night and Wednesday. A cold frontpassing through the region Wednesday night will bring thegreatest threat for restrictions in showers and possiblethunderstorms. During this period...MVFR/IFR restrictions arepossible...with fog also possible by Thursday morning. VFRdaytime Thursday-Saturday&&.MARINE...Short Term...SCA remains up for the open waters E of Casco Baymainly for seas, but could be some N winds gust to near 25 ktbriefly late tonight. Otherwise winds/seas will fall SCA levelson Tuesday.Long Term...Marginal SCA conditions in southerly winds onWednesday and Wednesday night ahead of an approaching coldfront. The next threat for SCAs does not arrive until lateSaturday.&&.GYX WATCHES/WARNINGS/ADVISORIES...ME...None.NH...None.MARINE...Small Craft Advisory until 5 AM EDT Tuesday for ANZ150-152.&&$$NEAR TERM...Cempa/CornwellSHORT TERM...CempaLONG TERM...Arnott