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. --579FXUS61 KGYX 172015AFDGYXArea Forecast DiscussionNational Weather Service Gray ME415 PM EDT Fri May 17 2024.SYNOPSIS...
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A weak trough will approach northern areas this eveningbringing scattered showers to the mountains. Low pressure movingup the East Coast will spread light showers into Maine andeastern New Hampshire Saturday. High pressure strengthens overthe region early next week with dry conditions and above normaltemperatures. Scattered showers return by late Wednesday intoThursday as a cold front approaches and then crosses the region.
-- End Changed Discussion --&&.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Impacts:*No significant weather impacts expectedMany areas warmed well into the 70s today which has resulted inan expansive cumulus field over most of the area, the exceptionbeing the coast where the seabreeze has kept things more stable.Current radar shows storms are starting to pop up in northernSomerset county and just over the International Border and Iwould still expect some to pop up in the Western Maine Mountainsand northern New Hampshire before today`s heating is done. Arumble of thunder with these is not out of the question as SPCmesoanalysis suggests upwards of 500 J/kg of surface based CAPEin that area. Otherwise, we will just be watching cloudsincrease as a trough approaches from the west, currently justgetting into New York based on satellite. These increasingclouds should largely keep low temperatures in upper 40s and low50s. As far as fog tonight, went with the persistence thinkingas I don`t see a reason that some patchy fog wouldn`t develop inthe valleys again tonight with winds light and low levelmoisture increasing. This will be especially true for the coastas an area of low pressure moves up the East Coast now lookingclose enough to push some decent moisture into the coastalplain, so kept marine fog in the forecast which may be able topush just inland into immediate coastal areas like Portland andRockland, but not much further.
-- End Changed Discussion --&&.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
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Impacts:* No significant weather impacts expectedLow pressure off at sea now looks like it will pass closeenough to spread showers into Maine and eastern parts of NewHampshire. Unfortunately, 12Z guidance did not provide much moreconfidence in the probability of precipitation. We willcertainly have clouds as we will be getting moisture advectionfrom both sides with the trough moving in from the west and lowpressure pushing it in from the east. Models do agree that thismoisture being advected in from the low will drive PWATs up near1.25". However, they greatly disagree on if we will actuallyget much rain out it. Mesoscale models have trendedsignificantly wetter over Maine with just a few scatteredshowers backing into New Hampshire. Global models have continuedto be unexcited and throw just a few light showers at theimmediate coast. Due to this uncertainty, I continued with amiddle of the road approach using the likely PoP coverage of themesoscale models for coastal and interior areas as it seemslike that will be the best chance to see at least some lightshowers. With that being said, I went very conservative withQPF, siding more with the global models, as the mesoscalemodels, that tend to over do it in these regimes, were spittingout 0.5" to 1" amounts across the Midcoast and interior. At thistime it seems more likely that these will be lighter showersthat would be more like .10" to 0.25" with the higher amountsbeing realized in those areas near the coast that see morenumerous showers. High temperatures will likely only just getinto the 60s away from the coast, with areas along theConnecticut River Valley standing the best chance to see highertemperatures in the upper 60s as they would be the first to seeskies clearing as the low pressure system pulls away.With subsidence behind the trough, its likely patchy fog willdevelop again Saturday night as areas clear out, especially inareas that saw rain. As a result, low temperatures look to onlydrop into the upper 40s and low 50s areawide.
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Overview: Two main pressure systems will influence conditionsover the area through the long term. First will be high pressurethat maintains quiet weather overhead for the second half ofthe weekend and into early next week. Second is approaching lowpressure and trough that could bring a round of widespreadrainfall to the area as well as the chance for somethunderstorms into midweek. Temperatures are forecast to risefor early in the week, perhaps by 10 to 15 degrees above normalfor southern portions of the area.Details: Ridging sits over the area Sunday with more stableconditions. While precipitation isnt expected, there willremain moisture in the low levels that is expected to leave muchof the area cloudy. Cant rule out drizzle considering some ofthe profiles looking saturated in the low levels, but any sortof lift is limited as well. Will hold off on drizzle wording fornow, but would expect at least some patchy drizzle into themorning and perhaps again in the evening. These conditions willleave temperatures mild, but went slightly lower than the meanconsidering the chance for cloud cover. Some breaks will bepossible on western side of the mountains, particularly in theafternoon, so left expected highs here closer to the mean (upper60s to around 70). With clouds expected to remain overnight,lows are also mild falling to around 50.Moisture layer will have thinned by the time Monday rollsaround, and currently forecast thinning clouds into theafternoon. This should be a good start to a warming trend forearly next week with highs pushing into the mid to upper 70s.The warmer temps arent expected until Tuesday/Wednesday whenreturn flow from exiting high really combines to push 850mbtemps above 10C.Well above normal temperatures are possible Tuesday andWednesday next week. The area will be in between weathersystems, with high pressure sliding east and incoming troughfrom the west. This should emphasize SW flow through much of thecolumn, resulting in good WAA. This would mean temps pushinginto the 80s for at least southern areas. NBM probabilities hintat temps perhaps exceeding 85 degrees up the CT River Valleyand interior southern NH, but areal extent outside of thoselocations isnt consistent.Another topic for mid week will be the return of forcing,moisture, and instability. Surface low pressure is forecast totrack up towards James Bay by Wednesday night, with anassociated warm front lifting through the region and cold frontexiting the eastern Great Lakes. This will create some favorableconditions for rounds of showers, but also some thunder. Thereremains differences in guidance to hone in on exacttiming/impacts, but can say the environment will be moreunsettled here especially on the heels of the warm/hotconditions. The front should pass off the coastal waters towardsFriday morning, with slightly cooler temps into next weekend.
-- End Changed Discussion --&&.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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Short Term...Mainly VFR this evening with some localizedrestrictions in fog at valley terminals and possibly coastalterminals as well. Fog will dissipate Saturday morning, butceilings will also be lowering so improvements may only be madeto MVFR. This will be the case through the day Saturday beforeskies clear again overnight Saturday. Again there will be achance for localized fog, but ceilings will be trending towardVFR for Sunday.Long Term...Ceiling restrictions expected Sunday, with mainlyMVFR and some IFR for much of the area. These remain overnightinto Monday morning, but begin to improve towards VFR into theafternoon. Low confidence in fog/vis restrictions at this time,but can`t rule out drizzle Sunday. VFR conditions Tues into Wed,perhaps some overnight valley fog.
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Short Term...SCA conditions begin to develop tonight as lowpressure moving over the eastern waters pushes 5 ft swell intothe area with winds not exceeding criteria. These elevated seaslook to last through Saturday night and begin subsiding Sundaymorning. Winds will be primarily northeasterly through thisperiod with gusts around 15-20 kts.Long Term...Wave heights remain around 5ft Sunday, but will bedecreasing overnight into Monday as high pressure takes upresidence. This should lead to sub-SCA impacts to wind/waves,but could also see some fog over water develop as warmertemperatures enter the region into early next week.
-- End Changed Discussion --&&.GYX WATCHES/WARNINGS/ADVISORIES...
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ME...None.NH...None.MARINE...Small Craft Advisory from 2 AM Saturday to 10 AM EDT Sunday for ANZ150-152-154.
-- End Changed Discussion --&&$$NEAR/SHORT TERM...BaronLONG TERM...Cornwell