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. --136FXUS61 KGYX 081117AFDGYXArea Forecast DiscussionNational Weather Service Gray ME717 AM EDT Thu Aug 8 2024.SYNOPSIS...High pressure builds in tonight and brings dry conditionsthrough Thursday. Another frontal system and tropical moisturewill bring heavy rain and a localized flood threat Friday intoSaturday. An unsettled weather pattern looks to continue throughat least mid-week as upper level troughs swing through theregion.&&.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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715 AM Update...Valley fog, especially in NH continues thismorning but will lift by 13z. Otherwise, a mostly sunny day isin store with temperatures in the 70s for most zones.A fair weather day is expected today with dry weather andtemperatures near average. A thunderstorm or two could sneaknorthward across the MA border around 00z this evening, butotherwise, we expected dry weather.
-- End Changed Discussion --&&.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...A warm frontal boundary will sharpen up well to our southtonight as the remnants of Debby moves northward into theAppalachians. The best forcing for ascent will be a mid levelfrontogenetical zone across northern zones and if there is anyorganized heavy rain overnight it will likely be in the northernmountains near the Canadian border. Otherwise, south of thethere, ridging will likely keep forcing for ascent relativelyweak with less rain expected.During the day of Friday, deeper-level ridging should stillkeep much of the heavy rain associated with the remnants ofDebby to our west. We can`t rule out a few showers andthunderstorms with heavy rainfall rates but for the most partmost locations should just see showers with the heaviest beingacross the Whites where a significant upslope wind component inthe lower levels may allow for more efficient rainfallprocesses.The main brunt of forcing for ascent will move through the regionFriday night and Saturday morning in the midst of significanttropical moisture (PWATS greater than 2 inches). The good thingis that it appears as that our CWA will not be involved with asignificant precursor rain event. We`ll be dealing with arelatively fast frontal passage in a very high PWAT air mass.This may portend to isolated to scattered flash flood events andperhaps even a couple thunderstorm wind events or even anisolated tornado as low level helicity increases to greater than250 J/Kg and sig tornado parameters increase to around 2 justahead of the front. The front moves offshore Saturday morningwith the rain ending and subsequent drying the rest of the day.&&.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...Unsettled weather will continue through the remainder of theextended forecast period as an upper level trough looks toapproach on Sunday night. The global models also hint at asecond trough mid week with variations in timing. Have kept withNBMs low chance PoPs as this messages the uncertainty in showerpotential and coverage well at this time range.&&.AVIATION /11Z THURSDAY THROUGH MONDAY/...Short Term...VFR conditions will dominate tonight throughThursday evening. The exception will be at valley TAF sitesincluding KHIE, KLEB, and KCON where valley fog is likely topersist through around 12Z today, resulting in IFR to LIFRrestrictions. Winds will be light and variable tonight beforebecoming southeasterly at 10-15 kts on Thursday afternoon.Ceilings will then gradually lower on Thursday night withscattered SHRA possible, especially after 04Z Friday. No LLWS isexpected.Long Term...Friday will start MVFR, but as the day goes on andceilings lower we will start to see more IFR. Friday night intoSaturday morning will feature low lower ceilings as heavy rainshowers traverse the area. Isolated thunderstorms are possibleduring this time as well. Ceilings return to VFR later in theday Saturday and prevail through Monday. Southerly winds couldbe gusting 20-25 kts Friday night into Saturday.&&.MARINE...Short Term...Winds and seas to remain below thresholds hazardousto small crafts as high pressure settles over the waters.Long Term...Winds and waves will be rising above SCA criteriabeginning Friday night. Sustained winds Friday night intoSaturday look to be 15-20 kts with gusts 25-30kts. Winds will besoutherly through the day Saturday, shifting westerly by Sundaymorning. Winds calm below SCA criteria Saturday night, but seaswon`t come down until Sunday night.&&.HYDROLOGY...WPC continues a slight risk for flash flooding in the Day 2 EROhighlighting some tropical moisture from Debby lifting into NewEngland Friday through Saturday morning. A frontal boundarynorth of the remnant storm will be a focus for heavy rainfallover the Northeast, regardless of the ultimate track of Debby`sremnant circulation. However, the timing and location of thisfrontal boundary is still somewhat uncertain. Widespread soakingrainfall is still expected, but with the track shiftingwestward it makes the flash flood threat more localized to areasin the White Mountains where SEly upslope flow will aid in warmrain processes.&&.GYX WATCHES/WARNINGS/ADVISORIES...ME...None.NH...None.MARINE...None.&&$$NEAR TERM...EksterSHORT TERM...EksterLONG TERM...Baron/Ekster