


Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
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304 FXUS61 KBOX 121848 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 248 PM EDT Sat Jul 12 2025 .SYNOPSIS... Seasonably warm and humid conditions continue this weekend. Chance for showers and thunderstorms across the interior into this evening, then trending drier for Sunday. A better chance for showers and thunderstorms then exists on Monday as a frontal system moves through. Increasing heat and humidity around the middle of next week, which then looks to break around Friday as a cold front brings yet another risk for showers and thunderstorms. && .NEAR TERM /THROUGH TONIGHT/... Key Points: * Continued warm and humid conditions Showers and thunderstorms were chained to the east slopes of the Berkshires this afternoon. Light SE flow across our region resulted in just enough upslope to trigger showers and thunderstorms in an otherwise mediocre environment. There is plenty of buoyancy, but very little shear. This makes it most likely that any thunderstorms rain on their own updraft, leading to shorter-lived storms. The risk is these storms were not moving much or fast. The main concern is downpours possibly leading to localized flash flooding. Already had to issue a Flash Flood Warning for portions of Hampshire and Franklin Counties. Past sunset, expecting stratus and fog to return to most locations across southern New England. It will remain quite muggy, so low temperatures tonight are perhaps a few degrees lower than what we had Saturday morning. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... Key Points * Dry with seasonably warm and humid conditions Sunday Not much change to the air mass Sunday and Sunday night. Thus, not anticipating much change to the forecast. Still thinking warm and humid conditions persist. Stratus and fog gradually dissipates after daybreak, then returns again after sunset. With a little more southerly flow, temperatures should be a little higher starting Sunday night. && .LONG TERM /MONDAY THROUGH SATURDAY/... Key Messages: * Better chance at more widespread showers/t-storms Monday. Threat for strong-severe storms low. * Very warm to hot during the middle of next week, with elevated heat indices around 95-100F. Heat headlines possible. * Becoming more unsettled late Thursday-Friday with increasing chances for showers/storms, especially Friday with a cold front. Details: Monday: Monday, a weak shortwave trough moves through the flow aloft. Overall, forcing is quite weak with a subtle passage of a front by Monday night. Daytime heating and the approaching wave will support marginal instability with MLCAPE values 100-1000 J/kg and MUCAPE values 200-1500 J/kg with the higher instability across western southern New England. Plenty of moisture with an axis of richer moisture positioned across the region, around 150-180% of normal. Enough ingredients here to support showers and thunderstorms in the afternoon-evening. Weaker winds aloft, will keep 0-6km bulk shear values low. As a result, the threat for severe/more organized storms will be low with regular thunderstorms more likely with brief gusty winds, heavy downpours. Can`t rule out a stronger storm or two, with gusty winds and small hail. Weaker winds aloft will yield slower storm motions, so we`ll have to watch for localized flash flooding potential in any storms. Highs temperatures will be in the low to mid 80s accompanied by higher humidity (65-75%). Tuesday-Thursday: Tuesday through Friday, a mid-level ridge builds over the regions. Temperatures aloft increase with 850mb temperatures peaking at around 20C in the Weds-Thurs timeframe. A good amount of moisture gets transported over the ridge by Wednesday adding humidity to the mix. Temperatures Tuesday through at least Thursday will range in the upper 80s to mid 90s with the exception of the immediate coast. With the the added element of higher humidity, it will feel more like mid to near 100 Wednesday and Thursday. Overall, there are no major disturbances embedded in the flow during that timeframe which will reduce the threat for widespread showers/thunderstorms. Ensemble members display potential for a few showers. Members are still spread across the board with timing and given the low coverage nature has been difficult to message in the forecast. Until better agreement on timing, no major adjustment have been made to the forecast. There will be a better signal for forcing later Thursday with corresponding increased chances for showers and thunderstorms. Thursday - Friday: A mid-level trough approaches the region, Thursday into Friday. This will shift the pattern to becoming more unsettled with increasing potential precipitation starting later Thursday. Ensemble members are still across the board when it comes the the precipitation chances and the timing leading to lower confidence this far out. A front will eventually push through on Friday with the main trough axis. This should bring the highest chances of seeing precipitation. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Today: Moderate confidence. With little change to the weather pattern, expecting low stratus and fog to lift and burn off between 14-17z, with the exception of the Cape and Islands where CIGS may remain low all day. VFR with pockets of MVFR again with lingering low level moisture. Chance for scattered showers and thunderstorms again this afternoon, although recent guidance has trended the activity further west. Went with prob30 for TSRA at western terminals for now, but future shifts may consider removing. Tonight: Moderate confidence. More IFR/LIFR Stratus builds north under light ESE flow. Sunday: Moderate confidence. IFR/LIFR stratus during the morning. VFR during the afternoon. KBOS Terminal...High confidence in TAF. IFR/LIFR CIGS through about 15z again, then VFR/MVFR through the afternoon. Low stratus deck likely again tonight. KBDL Terminal...High confidence in TAF. MVFR/IFR through about 13z, then CIGS gradually improve to VFR. Chance for thunderstorms again late this afternoon/evening, but the threat has trended further west. Outlook /Monday through Thursday/... Monday: Mainly VFR, with local MVFR possible. Chance SHRA, chance TSRA. Monday Night: VFR. Slight chance SHRA. Tuesday through Tuesday Night: VFR. Wednesday: VFR. Breezy. Wednesday Night: VFR. Slight chance SHRA. Thursday: Breezy. Chance TSRA, slight chance SHRA. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Today through Sunday...High confidence. Weak pressure gradient will keep winds/seas below Small Craft Advisory thresholds through Sunday: seas 2-4 ft with E winds over the southern waters and SE winds over the eastern waters up to 15 kts during the afternoon hours, remaining light in the overnight hours. Main concern for mariners will be areas of fog tonight that may redevelop Saturday night. Outlook /Monday through Thursday/... Monday through Wednesday: Winds less than 25 kt. Wednesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/Mensch NEAR TERM...Belk SHORT TERM...Belk LONG TERM...Mensch AVIATION...Belk/Mensch MARINE...Belk/Mensch