Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
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478 FXUS61 KGYX 151953 AFDGYX Area Forecast Discussion National Weather Service Gray ME 353 PM EDT Mon Jul 15 2024 .SYNOPSIS... Heat and humidity build for the next few days as high pressure strengthens off the Eastern Seaboard, with chances for scattered afternoon showers and thunderstorms each day. A cold front moves through late Wednesday through Thursday, bringing drier and somewhat cooler conditions for the end of the week and going into the weekend with high pressure building in from the west. && .NEAR TERM /THROUGH TUESDAY/... Visible satellite imagery this afternoon shows some diurnally driven cumulus across the area with some cirrus streaming over southern NH. The latest RAP13 pressure analysis shows a sfc trough moving across southern New England, which is helping to spark scattered showers and thunderstorms over Central Massachusetts. Latest CAMs suggest most of this activity should drift east and south of NH over the next couple of hours but it is possible some additional storms develop within the outflow boundaries associated with the ongoing convection. It will otherwise continue to be a hot and humid afternoon and early evening with just an isolated shower or storm. Any storm will be capable of producing locally gusty winds and briefly heavy rainfall. Our attention tonight will be focused on a gradually weakening MCS/MCV that is currently moving across western NY state. This system is progged to continue moving east-northeastward this evening and through tonight before arriving towards VT within an hour or so either side of 10 PM. Latest CAMs indicate a continued weakening trend as it arrives in our area by or a little after midnight with the main focus moving into southern Quebec. The environment will remain somewhat favorable though through the night for strong to locally severe storms as the h8 LLJ strengthens, increasing the 0-6km shear to around 35 kts with around 1500 J/KG of MUCAPE to work with. As a result, while the threat for overnight convection and possible strong to severe storms is low it cannot be completely ruled out as CAMs tend to struggle with these types of setups. Strong to locally damaging winds, heavy rainfall, and frequent lightning would be the primary threats. It will otherwise be a warm and muggy night with lows into the upper 60s to lower 70s. Patchy fog will be possible overnight as well. && .SHORT TERM /TUESDAY NIGHT/... Hot and humid conditions will persist on Tuesday with high temperatures into the lower to middle 90s south of the mountains. Cooler temperatures will be common across the far north, mountains, and along the Mid-Coast/islands. A Heat Advisory has been issued for most locations south of the mountains and away from the Mid-Coast with heat indices into the 95-100 degree range during the afternoon. Additional scattered showers and storms are possible during the afternoon and evening as a s/w crosses over the region. Any storms will be capable of becoming strong to severe with damaging winds the primary threat. The Storm Prediction Center has placed most of NH into a MRGL risk for severe storms. Storms diminish Tuesday night paving the way to another warm and muggy night with lows primarily into the 70s. Fog will be possible once again, especially in locations the receive earlier rainfall. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Models have been fairly consistent over the last few days for breaking the heat wave come Wed night and Thursday as a more localized -NAO sets up over Greenland and the Atlantic poleward of 50 N. This does help break down the ridge, but there is so much warm over central and western Canada that there really isn`t much of source to cool things down, but itll be more along the lines of less warm, with temps running normal or a little above. However, once we clear the hot air out, it will be mainly dry Friday into early next week, with daytime temps mostly in the 80s, and overnight light in the mid 50s to mid 60s. Wednesday shot be the last hot and humid days, and while we will probably need another heat advisory in S NH and SW ME, there are still questions as to how quickly clouds/SHRA/TSRA move in ahead of the front, and thus, how will warm it will be in points N and E. As for the front, there still questions with its timing as we will have to see how it reacts to the wave interacting with it Tuesday night, and then again a second wave that moves through late Wed night or Thu, and where and when the second one develops will be dependent on the first. So, while some SHRA/TSRA will be possible Wed afternoon, especially in the mtns, the bulk of any convection will likely be Wed night, and precip amts will depend on what happens with the front. Its unlikely that we will clear the high humidity out of here Wed night, although mins will be a little lower especially in the mtns, generally in the 60s. Thu will also depend on what happens with the front, but, as we often see with cold fronts in the summer, if it doesnt get through before dark, it will likely not mix down until nest morning, and because we may rain overnight into Thu morning, may not see the drier air mix down until later in the day, so, while it ill not be as hot but itll still be humid. The good news is, we should see the effect of that cold front by Thu night with clearing and lower humidity, with mins in the mid 50s in the mtns to 60 to 65 in the S. Friday through the weekend will be dry and sunny. More comfortable RH are expected Fri with highs 75-80 in the mtns and low to mid 80s in the S and lows Sat morning in the mid 50s to low 60s. Sat and Sunday will be a few degrees warmer, with highs mostly in the 80, but will start to see the RH creep up a bit by Sunday. Monday looks dry and warm as well. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... Short Term...VFR conditions dominate tonight through Tuesday night outside of any FG, which could result in IFR to LIFR restrictions. The greatest potential for this will be at KHIE, KLEB, and KRKD. Scattered SHRA and TSRA are possible late tonight and again Tuesday afternoon and evening with locally strong winds and +RA the primary threats. No LLWS is expected outside of any TSRA. Long Term...Some valley fog possible lingering into Wed morning, but should return to VFR through the rest of the day. Sct TSRA will develop inland during the afternoon as a front approaches and move through Wed night. This is the best to see several hours or more of flight restrictions as fog settles in behind any rain that does fall. Flight restrictions could linger into Thu morning, but should see improvement to VFR during the afternoon. Thu night through the weekend will be mainly VFR, the only exception being late night valley fog. && .MARINE... Short Term...South-southwesterly winds will persist through Tuesday night. Although winds will primarily remain below 25 kts, a few gusts to near 25 kts will be possible at times. Scattered showers and storms will remain possible, some of which will contain locally stronger winds. Seas will be at 2-4 ft, highest outside of the bays. Marine fog will be possible at times. Long Term...Generally winds/seas stay below SCA levels through the coming week, but could approach SCA gusts/seas Wed night into early Thu. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Heat Advisory until 8 PM EDT this evening for MEZ012-018>020- 023-033. Heat Advisory from noon to 8 PM EDT Tuesday for MEZ012-018>024- 033. NH...Heat Advisory until 8 PM EDT this evening for NHZ004-006- 008>010-012>015. Heat Advisory from noon to 8 PM EDT Tuesday for NHZ004-006- 008>015. MARINE...None. && $$ NEAR TERM...Tubbs SHORT TERM...Tubbs LONG TERM...Cempa