943 FXUS61 KBOX 301512 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 1112 AM EDT Fri Jun 30 2023 .SYNOPSIS... Expect a mostly dry and warm Friday and Saturday, with temperatures from the low to mid-80s. Humidity returns Sunday, Monday and Independence Day along with the risk of scattered showers & thunderstorms, but not expecting a washout with many hours of dry weather each day. Trending drier next Wednesday and Thursday, but warmer than normal temperatures may finally make their arrival in southern New England. && .NEAR TERM /UNTIL 8 PM THIS EVENING/... Highlights... 10 AM Update... Fog is still lingering in the CT river valley, but for areas without fog, diurnal cumulus clouds is already starting to form. Areas that have broken out of the fog have seen temps rise rapidly this morning with Bedford and Norwood already approaching 80F. High res guidance continues to keep the region dry this afternoon outside of an isolated shower. Any showers that do form will be light and short lived due to significant mid level dry air. && .SHORT TERM /8 PM THIS EVENING THROUGH 6 PM SATURDAY/... Highlights... * Could see some drizzle or a couple showers over the Cape & Islands tonight, along with the return of low-stratus clouds. * Saturday looks to be the pick of the weekend with a mostly dry afternoon and seasonably warm temperatures. Tonight: Low-stratus likely redevelops over the outer Cape and the Islands once again, can not rule out drizzle or perhaps an isolated shower here. Otherwise, tonight will be mostly dry across the rest of the region. Overnight low temperatures are in the low to mid-60s. Saturday: Low amplitude mid-level ridge to the west of our region and subtle height rises should allow for a pleasant day. Clouds cover does increase later into the day as higher PWATs are advected into southern New England. By no means are we expecting any washouts, but similar to the past few days a rouge shower can not be ruled out. Afternoon temperatures are a few degrees warmer Saturday afternoon with highs in the low to mid-80s, while those going to the beach have temperatures a few degrees cooler in the upper-70s. It will feel muggy as dewpoints climb during the afternoon into the mid-60s. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Highlights... * Humidity returns Sun, Mon & Tue (July 4th), with scattered showers & t-storms too but not a washout with many hours of dry weather * Drier weather Wed & Thu but highs may reach upper 80s/lower 90s Details... Saturday night & Sunday... Shortwave trough moving across the eastern Great Lakes will induce a modest southerly LLJ late Saturday night into Sunday. This will result in a fairly rapid change in elevated stability indices. Most of the guidance indicates Showalter Indices dropping from around 10 to below zero within a 6 hour window. While timing remains uncertain...modest forcing with the rapid change in stability parameters should result in a round or two of scattered showers and perhaps a few elevated thunderstorms. Not expecting a washout...but the showers may contain pockets of brief torrential rainfall with Pwats climbing to around 2 inches. A fair amount of clouds and scattered showers should hold high temps in the upper 70s to the lower 80s on Sunday...but it will be rather humid. Monday and Tuesday (July 4th)... Shortwave trough will approach from the west on Monday and probably cross the region sometime Tuesday (July 4th). Surface trough approaching from the west on Monday coupled with modest jet dynamics/instability should trigger scattered showers and thunderstorms...particularly during the afternoon and evening. The potential is there on Tuesday (July 4th) as well...but that will depend upon the speed of the surface/pre-frontal trough. A slower passage would result in an increased risk for additional scattered showers and thunderstorms...while a faster passage would limit this potential especially across our western sections. It is too early to make that determination at this point. All we can say at this time is that scattered showers and thunderstorms are possible Mon & Tue. While a washout is not expected...both the CIPS Severe Analogs and the Colorado State Machine Learning Probs continue to indicate at least a low risk of severe weather. This is certainly reasonable with a modest upper level jet/instability and potential for 70+ dewpoints. A localized flood threat will also exist with these storms given Pwats near 2 inches. Time will tell if this is realized...but certainly something we will need to watch closely. High temperatures both Monday and Tuesday (July 4th) mainly in the 80s but it will be quite humid especially on Monday. Wednesday and Thursday... The upper trough will have pushed east of the region by Wednesday and Thursday. This should favor mainly dry weather but we may finally see above normal temperatures. In fact...GEFS/EPS indicate slightly above normal height fields and 2 meter temperature anomalies. Given that we will likely see more sunshine by Wednesday and Thursday...high temperatures in the upper 80s to the lower 90s may finally arrive. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 15z TAF Update...no change from 12z TAFs - VFR, dry runways and light and variable winds, except ESE for coastal terminals. Earlier discussion below. ---------------------------------------------------------------- Today...High confidence. Any lingering IFR-LIFR conditions in patchy dense ground fog will improve to VFR by 14z/15z. Otherwise...nothing more than a brief localized spot shower this afternoon. Winds out of the S except for eastern coastal spots where localized sea breezes develop between 13z to 15z. Tonight...Moderate confidence. IFR-LIFR conditions develop towards the Cape/Islands in low clouds and fog...some of which will be locally dense. Across the rest of the region...VFR this evening but expect areas of IFR- LIFR conditions in ground fog to develop some of which may be locally dense in the typical spots. Saturday...High confidence. VFR. Brief spot shower possible across the interior during the afternoon. Light south winds. BOS Terminal...High confidence in TAF. South wind, should sea breeze by 13-14z. BDL Terminal...High confidence in TAF. Outlook /Saturday Night through Tuesday/... Saturday: VFR. Slight chance SHRA. Saturday Night: Mainly VFR, with local MVFR possible. Chance SHRA. Sunday: MVFR/IFR conditions possible. Chance SHRA, isolated TSRA. Sunday Night: Mainly VFR, with areas IFR possible. Chance SHRA, isolated TSRA. Monday: Mainly VFR, with areas MVFR possible. Chance SHRA, isolated TSRA. Monday Night through Independence Day: Mainly VFR, with local IFR possible. Chance SHRA, isolated TSRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Through Friday Night...High confidence. This morning stratus and fog with 1/4 to 3SM visibility especially across the southern waters, but also into portions of the eastern outer waters. The stratus burns off mostly before developing/advecting back in Fri night into early Sat. Winds out of the S at 5-10 kts. Saturday...High confidence. Areas of morning stratus and fog, which should burn off by late morning. Chance of a shower during the afternoon, otherwise a dry day with winds and seas below SCA criteria. Outlook /Saturday Night through Tuesday/... Saturday Night through Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers. Sunday Night through Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, isolated thunderstorms. Monday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers, isolated thunderstorms. Independence Day: Winds less than 25 kt. Chance of rain showers, isolated thunderstorms. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Air Quality Alert until 11 PM EDT this evening for CTZ002>004. MA...Air Quality Alert until midnight EDT tonight for MAZ002>004- 008>012. RI...None. MARINE...None. && $$ SYNOPSIS...Frank/Dooley NEAR TERM...Frank/Dooley/KP SHORT TERM...Dooley LONG TERM...Frank AVIATION...Frank/Nocera/Dooley MARINE...Frank/Dooley