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. --724FXUS61 KGYX 131937AFDGYXArea Forecast DiscussionNational Weather Service Gray ME337 PM EDT Thu Jun 13 2024.SYNOPSIS...
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A cold front will cross the region on Friday...bringing thescattered showers and thunderstorms to the region. Cooler anddrier air will build in for the weekend. Next week...a largeridge of high pressure will build towards the northeasternUnited States with warming temperatures. An extended period ofsignificant heat is expected to develop by Tuesday and continuethrough the remainder of the week with most location seeing hightemperatures in the 90s.
-- End Changed Discussion --&&.NEAR TERM /THROUGH TONIGHT/...
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High clouds gradually increase overnight tonight as a coldfront approaches. The clouds and southerly flow help to keeplows mainly in the 60s overnight. Some showers from thisafternoon`s convection begin to push into northern areas aftermidnight, and will slowly diminish in coverage as they movetoward the coastline through the daylight hours tomorrowmorning. A few thunderstorms are also possible overnight towardthe Canadian border, but these are also expected to weaken asthey move southeastward.
-- End Changed Discussion --&&.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
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The front gradually moves through the area during the daytimetomorrow. Morning showers give way to a mix of sun and clouds,allowing temps to warm into the upper 70s to low 80s south ofthe mountains with increasing dew points. Southeastern NH standsthe best chance to warm into the mid 80s with a bit moresunshine. Across the mountains, more showers and a fewthunderstorm begin to develop again by the early afternoon.These then progress southeastward through the day with thefront.The best chance for some strong to severe storms continues tobe across southeastern and southern New Hampshire, where thegreatest heating and shear look to combine. Some isolated strongto severe storms are also likely elsewhere across the coastalplain during the mid afternoon, but it looks like the front willbe clearing the coastline too early in the afternoon to causemore of a concern. Some heavy rainfall is also possible,especially across southeastern New Hampshire where a couplerounds of storms are possible, and could cause some localizedissues that will need to be monitored.Showers and a few thunderstorms gradually diminish along thecoastline through the evening and into the overnight hours asthe front moves offshore. A developing area of low pressurepassing offshore helps to slow the front a bit and keeping theshowers near the coast through the overnight, so only gradualclearing is expected by daybreak on Saturday. Cooler and drierair begins to make its way into northern areas tomorrow night,with lows dropping to near 50 degrees.
-- End Changed Discussion --&&.LONG TERM /SATURDAY THROUGH THURSDAY/...
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...Multi Day Heat Expected Next Week...High Impact Weather Potential: Multiple days of heat indices inexcess of 95 to 100F beginning Tuesday likely continuing through theend of the week. The potential exists for heat indices in excess of105F especially over southern NH and SW ME.--Pattern and Summary--The long term period opens with a mobile longwave trough overheadwhich will move east of the region by Sunday. Beyond this...asignificant pattern change is in the works...with longwave troughingdigging down the west coast of North America which will help pushwestern US ridging to the east. The result will be a building ridgeacross the eastern half of the United States on Tuesday with thisridge locking in place over the northeast for the middle and latterportions of the week. This ridge looks to be rather impressive forany time of the summer...not to mention mid June...with H5 returnintervals approaching or exceeding 30 years by Wednesday andThursday and nearing the top end of the GYX sounding climatology.Thus...the primary forecast concern for the long term will center ontemperatures rather than precipitation as the proximity of the ridgenext week will likely preclude much in the way of rainfall whiletemperatures will potentially near record highs centered around thefirst day of astronomical summer.--Daily Details--Saturday - Sunday: One last stretch of dry and seasonable weather isexpected to open the period this weekend as offshore cold frontpushes east on Saturday with Canadian high pressure buildingoverhead for Sunday. The ensemble guidance envelope includes somemembers that have a few showers along the coast as the frontalboundary slows over the Gulf of Maine...but expect the day tofeature morning clearing...seasonable temperatures /highs in theupper 60s in the mountains to the upper 70s across southern NH/ anddramatically lower dewpoints than on Friday. This sets up a goodradiational cooling night Saturday night with 40s common across thearea. Expect some of the northern valleys will dip again into theupper /and perhaps middle/ 30s. Sunny weather expected for Father`sDay with T8s in the upper single digits suggesting highs in the 70sto around 80 from north to south.Monday: High pressure settles south of Maritime Canada with deeplayer ridging building towards the region from the west will allowreturn flow to strengthen...with temperatures building to star theweek. Monday looks seasonably mild with nearby high pressure /weakgradient/ indicating a robust sea breeze with highs along the coastin the 70s...and temperatures reaching the lower to middle 80sinland.Tuesday - Thursday: T8s push into the upper teens by Tuesday withsome potential to push above 20C by Thursday...which represents a 1in 10 year to 1 in 30 year event for this time in June. Fullymixed...+20C suggests mid 90s which is well-captured by the NBM forWednesday/Thursday. This is right in the vicinity of daily recordsfor this period /for example...CON for Tuesday, Wednesday, andThursday is 98F/. A slightly more southerly trajectory to thegradient should allow the immediate coast to stay cooler on Tuesday/ 70s to lower 80s / with a seabreeze but by Wednesday and Thursdaythe gradient turns more westerly with the heat pushing to the coast.Dewpoints begin the period in the lower 60s on Tuesday...and theninto the mid/upper 60s by Wednesday-Thursday with some ensemblemembers going higher than this. While a few ensemble members have aconvective complex trying to push into our area at some point in theextended...this has little ensemble support and conceptually doesn/tfit given our proximity to the center of the ridge. Thus...willmaintain a dry forecast through the period.
-- End Changed Discussion --&&.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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Short Term...VFR prevails through the overnight, with some MVFRceilings and scattered showers reaching LEB and HIE during theearly daylight hours. Periods of MVFR and showers continue atLEB and HIE much of the day, while the remaining terminals seebrief restrictions with showers and a few thunderstorms in themid to late afternoon. Showers linger across coastal terminalsinto the evening, and then VFR returns Friday night. Some valleyfog may bring restrictions late tomorrow night.Long Term...Any lingering showers should depart the regionearly Saturday...with VFR conditions and northwesterly winds10kts before winds diminish Saturday night with light winds/VFRconditions Sunday through Tuesday.
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Short Term...South-southwesterly winds freshen ahead of anapproaching cold front tonight, with marginal SCA conditionsdeveloping after midnight. SCA conditions continue tomorrow,then the front crosses the waters tomorrow evening with showersand thunderstorms. High pressure begins to build across thewaters by late tomorrow night.Long Term...High pressure builds over the waters this weekendbefore settling south of the waters early next week. Given thissetup, winds/waves are expected to remain below SCA levelsthrough the long term period.
-- End Changed Discussion --&&.GYX WATCHES/WARNINGS/ADVISORIES...ME...None.NH...None.MARINE...Small Craft Advisory from 1 AM to 8 PM EDT Friday for ANZ150- 152-154.&&$$SYNOPSIS...ArnottNEAR TERM...ClairSHORT TERM...ClairLONG TERM...ArnottAVIATION...Arnott/ClairMARINE...Arnott/Clair