


Area Forecast Discussion
Issued by NWS Portland, ME
Issued by NWS Portland, ME
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336 FXUS61 KGYX 080611 AFDGYX Area Forecast Discussion National Weather Service Gray ME 211 AM EDT Tue Jul 8 2025 .SYNOPSIS... The heat winds down today, with hot temperatures mainly confined to York county and the Seacoast. A front finishes crossing the area this afternoon and evening providing the forcing for showers and storms. Showers and storms today are capable of producing heavy rain, and pose a localized flash flood risk for locations that see repeated rounds of them. Chances for afternoon showers and storms stay in the forecast through the rest of the week. Temperatures will be cooler for the second half of the week. && .NEAR TERM /THROUGH TODAY/... Impacts and Key Messages: * Heat indices will reach the mid 90s again in southeastern New Hampshire. * Localized flash flooding is possible along the coastal plain tomorrow afternoon as tropical moisture will aid in the development of heavy rain. Isolated amounts greater than 2" are possible in areas that see repeated rounds of heavy showers/storms. Heat: The frontal boundary remains hung up north of the mountains which will allow for one more day of hot and humid conditions in southeastern New Hampshire where high temperatures are likely to climb into the low 90s. With dewpoints still around 70F south of the front, this will feel more like the upper 90s. The Heat Advisory remains in effect with no changes. Locations outside of the heat advisory, should start to feel the effects of the frontal passage as drier and cooler air fills in behind the front,or the cooling effects of thunderstorms. This will make for a stark temperature contrast across the area, with locations north of the mountains in the 70s and locations to the south in the low to mid 80s. The southern Maine Coast likely will see temperatures in the upper 80s to near 90, which may approach heat indices in the mid 90s, but this is also the area where confidence is higher for heavy rain and thunderstorms so it might not last as long and therefore I do not plan to expand the Heat Advisory. Thunderstorms: Modest CAPE approaching 1000 J/kg will develop as a result of daytime heating and be supportive for thunderstorms this afternoon as the frontal boundary slowly sinks southward, but weak shear (only around 20 kts) and lapse rates (only around 5.5-6 C/km) should keep them loosely organized and sub severe. Heavy Rain: This is the most concerning threat for this afternoon as tropical moisture from the remnants of former TC Chantal become entrained along the frontal boundary, driving PWATs up near 2" over the coastal plain. Forecast soundings show potential for very efficient warm rain processes as warm cloud depths exceed 12kft. Forecast soundings are also supportive of back building and training storms with Corfidi vectors around 5 kts, and with mid level flow only around 20kts or less, these storms won`t be the quickest movers. Current 1 hr Flash Flood Guidance is still on the high end on the coastal plain (around 2.5-3"/hr) so any one storm isn`t as likely to cause issues. However, 3 hr flash guidance is only a bit higher (3-3.5") and I feel like this could be achieved fairly easily at any location that experiences training of storms. Hi-res guidance has been suggesting isolated bullseyes of 3"+, mainly targeting the Maine coast, but there is plenty of uncertainty in where exactly training might set up. With the uncertainty in exact location and what looks like a more isolated flash flooding threat, don`t see a need for a widespread Flash Flood Watch. We can handle areas of concern with short fuse warnings. WPC does have much of the I-95 corridor up to Portland, in a Slight Risk ERO. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY/... Impacts and Key Messages: * No significant weather impacts expected Tonight: The front looks to finally clear the coast tonight which will bring heavy showers to an end, with some lingering light showers possible through the night as the region gets more under a broad troughing pattern. The actual remnants of former TC Chantal will make a close pass in the early hours of Wednesday morning which may bring some additional showers into southern New Hampshire, but there is uncertainty between models on just how far north these will come. Otherwise, low temperatures look to drop into the low to mid 60s which should feel much more pleasant compared to the last few nights. Wednesday: Broad troughing over the region will support a chance for scattered showers during the day Wednesday and maybe some rumbles of thunder as latest CAMs suggest a couple hundred joules of CAPE may develop. Otherwise it looks like a pleasant summer day with high temperatures in the mid to upper 70s. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Evening Update...No significant changes to the long term period with the inclusion of the latest NBM. Chances of showers and afternoon thunderstorms remain in the forecast late week as a trough swings through. Global models are beginning to hint at the potential for a drier weekend with deep layer ridging potentially building in. The beginning of next week looks unsettled as another trough approaches the region. Previous Discussion... The second half of the week and next weekend will feature cooler temperatures and unsettled weather. High temperatures look to be in the 70s Thursday and Friday as ensemble guidance suggests a weak mid-level trough moves in from the west. Some weak forcing and daytime destabilization may allow for some diurnally driven showers and thunderstorms to form on Thursday and Friday afternoons. Thunderstorm chances look to be the highest on Thursday, especially in the CT River Valley and locations north of the mountains. The 500mb trough will slowly loosen over the weekend, with some warmer high temperatures on tap to start next week. Saturday and Sunday, highs look to be near 80F most places, with lower 80s early next week. Next weekend looks mostly dry, though a shower or two can`t be ruled out. More unsettled weather is possible to start off next week. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... Short Term...Showers and thunderstorms are possible at all terminals this afternoon, but confidence is highest at AUG, PWM, and RKD so that is where they are included in the TAFs at this time. Once showers and storms clear the area Tuesday night, fog is likely to develop, especially in areas that saw rain during the day. After any fog burns off Wednesday morning, the remainder of Wednesday should see VFR prevail with just some scattered showers and an isolated storm, during the afternoon that may cause a brief restriction. Long Term...Generally VFR is expected through most of the extended, though scattered showers and thunderstorms in the second half of the week could allow for some brief restrictions. && .MARINE... Short Term...Wind gusts and seas remain below SCA criteria through Wednesday. Winds will shift onshore with the passage of a front tonight. Long Term...2-4ft seas are expected through the second half of the week, with easterly winds at 5-12kts expected. No SCA issuance expected for the time period. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for NHZ010-012>014. MARINE...None. && $$ NEAR TERM...Baron/Legro SHORT TERM...Baron/Legro LONG TERM...Baron/Palmer