440 FXUS61 KBOX 071142 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 742 AM EDT Mon Jul 7 2025 .SYNOPSIS... Higher than normal heat and humidity expected today with a Heat Advisory in place. Unsettled weather makes a return late today into tonight, continuing off and on through much of next week. Tuesday some isolated severe storms are possible as well as heavy downpours and localized flash flooding. Cooler weather expected mid to late week. && .NEAR TERM /THROUGH TONIGHT/... Key Messages... * Mild this morning with patchy fog for the south coast and islands. * Warmer than normal today and very humid. * Isolated showers and thunderstorms in the afternoon, mainly for western CT and MA. Have begun to see satellite and surface ob evidence of fog/low stratus mentioned by the previous forecaster making its way slowly north/inland into the south coast/coastal plain of MA and southern RI. Hi-res guidance continues to indicate this should be confined south of the MA Pike, if that far north; model soundings indicate that these low clouds could be confined to the Cape/islands and the immediate coastline which I think is most likely. Even after sunrise, hi-res guidance indicates it may be hard to mix out these low clouds even through the afternoon. Elsewhere, though, a mix of clouds and sun is expected today as weak mid level ridging keeps things mostly quiet/dry to start. Toward the latter half of the day a shortwave approaches SNE which will act on abundant/anomalous moisture (PWAT plume of 2+ inches) to produce scattered showers and thunderstorms, most likely in western MA and CT. Forcing is quite weak for any storms, as are bulk shear values and mid level lapse rates. This means that while we have lower confidence of exactly where thunderstorms will form, any that do should not be severe. They will, however, have the low chance for heavy downpours and localized flash flooding. The greater concern, though, comes on Tuesday with the arrival of better forcing ahead of the cold front. Heat and humidity remain, and it is within the realm of possibility that the Heat Advisory will need to be expanded into Tuesday for some areas. However, confidence is not high enough that the same locations that saw the highest apparent temps on previous days will experience temps necessitating an extension at this time. Tonight we remain in the warm, muggy environment keeping lows very mild, limited by the elevated dewpoints, in the low 70s. Fog and low stratus will likely be more widespread with near zero dewpoint depressions. Showers are possible overnight, mainly over southeastern New England associated with convergence around a weak surface low. && .SHORT TERM /TUESDAY/... Key Messages... * Showers and thunderstorms Tuesday. * Isolated strong to severe storms possible with heavy downpours and potential for localized flash flooding. Tuesday the unsettled weather will be more widespread across southern New England as synoptic and mesoscale forcing for ascent increase with passing of a mid level vort max and approaching surface cold front. Temperatures in the upper 80s/low 90s with dewpoints in the 70s will contribute to instability on the order of 1500-2000 J/kg of CAPE. However, other parameters are less favorable for severe weather, namely mid level lapse rates near 5-5.5 C/km and 0-6km bulk shear <25kts. Even so, can`t rule out an isolated strong to severe storm producing damaging wind gusts. The greater risk given the weak steering flow and abundant aforementioned moisture/skinny CAPE profiles will be heavy downpours leading to flash flooding. The area remains within a Marginal Risk (level 1 of 4) of excessive rainfall leading to flash flooding Tuesday, especially Tuesday afternoon and evening. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Key Messages... * Periodic chances of unsettled weather each day through at least Friday. * Seasonable to even cooler than average temps by late week. A steady stream of moisture is directed into New England with PWATs near 2 inches clear through at least Thursday. This together with quasi-zonal flow and periodic mid level disturbances moving through the mid level flow will lead to chances for showers and thunderstorms essentially each day through at least Friday. Following that there are hints of a mid level ridge approaching for the weekend, but too soon to nail down timing on this feature. What`s more certain is the return to seasonal to cooler than average temperatures by Thursday into the weekend courtesy of onshore/easterly flow combined with a cooler airmass aloft. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 12Z update... Today...Moderate confidence. MVFR to IFR along the south coast of RI and MA scattering out 12-14z. Cape/Islands struggle to improve today, gradually improving into the early afternoon. SSW to SW winds 10-15 kts, gusts 20-24 kts by early afternoon. Isolated showers and few thunderstorms may develop after 16z, but low confidence on where any storms will form. Tonight...Moderate confidence. IFR cigs expand from the south coast into most terminals by 06-10z. Winds light. Tuesday...Moderate confidence. VFR. W winds 5-10 kts. Scattered SHRA/TSRA with heavy downpours likely in the afternoon and evening. KBOS Terminal...Moderate confidence in TAF. Low clouds develop to the south early this morning, but are unlikely to reach the terminal. BKN mid-level ceilings Monday with SW winds with gusts around 20 kts in the afternoon. Low chance for an isolated shower/storm makes it east to to BOS after 18z. KBDL Terminal...Moderate confidence in TAF. Forecast confidence is moderate beyond 10z with the potential for lower ceilings. Isolated -SHRA/-TSRA possible after 16z. Outlook /Tuesday Night through Friday/... Tuesday Night through Wednesday Night: Mainly VFR, with local IFR possible. Chance SHRA, slight chance TSRA. Thursday through Thursday Night: Mainly VFR, with areas IFR possible. Chance SHRA, slight chance TSRA. Friday: Mainly VFR, with local IFR possible. Slight chance SHRA, slight chance TSRA. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Today and tonight: High confidence. After a brief lull this morning, SW winds increase in the afternoon to 10-15 kts with gusts 20-25 kts on southern waters, 25-30 kts on the eastern waters. Will likely need a SCA for the north outer waters zone. Seas 2-3 ft, increasing to 2-4 ft on the outer waters late in the day. Seas increase to 5 ft for the southern outer waters after overnight into Tuesday. Tuesday: High confidence. SW winds 15-20 kts with seas 2-4 ft on the eastern waters, 3-6 ft on the southern waters. Outlook /Tuesday Night through Friday/... Tuesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, chance of thunderstorms. Wednesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, slight chance of thunderstorms. Wednesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers, slight chance of thunderstorms. Thursday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers. Thursday Night through Friday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, slight chance of thunderstorms. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Heat Advisory until 8 PM EDT this evening for CTZ002>004. MA...Heat Advisory until 8 PM EDT this evening for MAZ003>007- 010>019-026. RI...Heat Advisory until 8 PM EDT this evening for RIZ001>004. MARINE...None. && $$ SYNOPSIS...BW NEAR TERM...BW SHORT TERM...BW LONG TERM...BW AVIATION...BW/McMinn MARINE...BW