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. --239FXUS61 KGYX 282314AFDGYXArea Forecast DiscussionNational Weather Service Gray ME714 PM EDT Fri Jun 28 2024.SYNOPSIS...High pressure over the region tonight will push south and eastof New England on Saturday with a warm front lifting through thearea by late in the day. This will result in increasing chancesfor showers by late Saturday with rain and embeddedthunderstorms Saturday night. Rain will taper off early Sundayahead of an approaching cold front with the potential foradditional showers and thunderstorms Sunday afternoon. Highpressure arrives early next week bringing a period of quietweather and seasonable temperatures.&&.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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715 PM Update... A rather pleasant Summer evening continuesacross the region with mainly clear skies and warm temperatures.Latest satellite imagery indicates the cirrus shield is stillrather far away in VT and Quebec and therefore given the low dewpoints and weakening winds, temperatures will likely fallrather abruptly over the next few hours. Will continue tomonitor these cloud trends and the associated impacts toovernight lows.Previously...High Impact Weather Potential: None.Pattern: The shortwave trough responsible for ushering in a muchcooler and drier airmass is now moving east of the region as seen onearly afternoon GOES 16 water vapor imagery. Surface high pressurenow over southern New England will slowly sag south and eastoffshore with the flow aloft slowly backing ahead of the nextshortwave arriving into the Great Lakes region. Overall this spellsa quiet night weather-wise with the focus of the forecast being oncloud cover and overnight lows.Through this evening: Temperatures should quickly drop in the dryairmass with some high clouds overhead. 8pm temperatures will dipbelow 60 in the mountains while remaining in the 60s to the south.Tonight: High pressure settles south and east of the area overnightas warm advection pattern sets up in the return flow as the H8 ridgeaxis passes to our east. The result will be top-down saturationwith mid and upper level cloudiness increasing. The result will besomewhat warmer temperatures with lows generally in the 50s acrossthe area under light winds.
-- End Changed Discussion --&&.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...High Impact Weather Potential: Locally heavy rain possible Saturdaynight.Pattern: Low pressure north of the western Great Lakes earlySaturday will move north and east through the short term forecastperiod remaining well north of New England through Saturday night.Saturday: Southwesterly flow continues to strengthen during the dayas surface warm front approaches the region from the southwest. Topdown saturation will continue through the morning with ample dry airremaining below H85. By late in the day...there is good short termmesoscale ensemble agreement that some showers will work into thenorthern zones given continued isentropic ascent in the area ofdeepest moisture. No convection expected with no instability towork with through evening. Despite warm advection...the southerlymarine-influenced flow along with increasing clouds will not yieldany significant warming of surface temperatures with highs againaround 70 in the mountains and in the lower 70s to the south. Someof the mesoscale guidance is hinting at the midcoast through theCapitol region also struggling to reach 70.Saturday Night: Robust...broad LLJ at H8 crosses the New EnglandSaturday night with MUCAPE plume overspreading the region as thewarm front finally drives through northern New England. This occursin the presence of significant deep moisture...with PWATs around 2"pushing above the 30 year climatology values. Deep forcing is a bitmore questionable. There is a weak mid level vort max in thepresence of weak height falls with modest right entrance region jetforcing moving overhead overnight in advance of the surface coldfront. Thus...despite increasing warm cloud depths in the presenceof significant moisture...the overall ensemble signals for heavyrainfall have decreased over the past 24 hours...favoring areasacross northern New York. A consensus forecast approach favors basin-wide average QPF of 0.5 to 1"...which also lines up well with themost recent runs of the HRRR and NAM Nest. Certainly some potentialfor locally heavy downpours given the environment focused over themountains matching well with the day 2 marginal excessive rainfalloutlook from WPC. Temperatures will be much warmer than the nightprevious as the warm front lifts through the region with southern NHlikely to remain in the upper 60s...with upper 60s to lower 60selsewhere across northern New Hampshire and western Maine.&&.LONG TERM /SUNDAY THROUGH FRIDAY/...I suppose its safe to say we have worked our way into a typicalsummer pattern as 500 MB ridging take residence S of the Mason-Dixon line, and troughs in north-shifted jet stream. Aregenerally flatter and more mobile. We start off a little on thecool side but the trend will be fore warming to near and abovenormal 850 MB temps by mid to late week. The tricky part is whatbecomes of the closed low that shifts to our SE late in theweek and whether it acts as a block to allow S_SW flow tosettle, making for another round of hot/humid weather or keepflow more zonal which will lead to more typical summer wx. Asfor chances of shra/tsra, beyond Sunday, we do see some of wavemove to our N around Wed-Thu.On Sunday will see a cold front, trailing fro low pressuremoving just N of the St. Lawrence valley cross the CWA. 12Z Euroshows a generally less dynamic system aloft associated with thefront, but there should be a surge in low level moisture andinstability ahead of it Sunday morning, so cannot rule outSHRA/TSRA, although less certainty about the potential forsevere that day. Behind the front, we do a surge of cooler air,and very dry air at least for Mon-Tue, with highs a little belownormal on Monday, but nice otherwise, and warming back to nearnormal on Tuesday. Wed will be warmer still with a bit ofincrease in humidity, but should stay dry most of the day.Wednesday night and Thursday are the next chance of precip, buttheres still a lot of uncertainty with this weaker system.&&.AVIATION /23Z FRIDAY THROUGH WEDNESDAY/...Short Term...Summary: High pressure builds south and east of the region tonightwith southerly winds strengthening on Saturday as clouds slowlylower. A warm front crosses Saturday evening with deterioratingconditions in rain and embedded thunderstorms.Restrictions: VFR conditions expected to dominate through the daySaturday. Showers with embedded thunderstorms arrive Saturday nightwith conditions deteriorating to MVFR/IFR CIGS and MVFR VSBYS.Winds: Northwest winds 10g18kts will diminish through this eveningbefore going calm/light-variable for the overnight. For the day onSaturday winds turns southerly and strengthen to 10g18kts for theday. Winds remain southerly around 10kts for Saturday night.LLWS: LLWS is not expected through Saturday. Saturday night...astrengthening low level jet will result in LLWS throughout theregion.Lightning: No lightning is expected through Saturday. Showers withembedded thunderstorms are expected across the terminals Saturdaynight.Long Term...Mainly VFR Sun-Wed, although some restrictionspossible in SHRA/TSRA Sunday. Also valley fog possible atKHIE/KLEB Sun and Mon night.&&.MARINE...Short Term...Quiet conditions over the waters through earlySaturday as high pressure crests over the waters. Southerlywinds strengthen Saturday afternoon and Saturday night with SCAslikely necessary for this period.Long Term...SW flow ahead of cold front will allow for SCA condson Sunday, but these4 drop off Sun night, and stay below SCAlevels through mid-week.&&.GYX WATCHES/WARNINGS/ADVISORIES...ME...None.NH...None.MARINE...Small Craft Advisory from noon Saturday to 4 PM EDT Sunday for ANZ150>154.&&$$NEAR TERM...TubbsSHORT TERM...ArnottLONG TERM...Cempa