NATIONAL WEATHER SERVICE BOSTON/NORTON MA
646 AM EDT WED JUL 24 2024
NEAR TERM /UNTIL 6 PM THIS EVENING/635 AM UPDATE
JUST A FEW LIGHT SHOWERS ACROSS SNE EARLY THIS MORNING WITHADDITIONAL SHOWER ACTIVITY AND A FEW STORMS FURTHER SOUTH ACROSS MID ATLC REGION AND OVER THE OCEAN WEAK SHORTWAVE WITHINTHE SW FLOW ALOFT WILL BE MOVING ACROSS THE REGION THIS AFTERNOON LEADING TO SCATTERED SHOWERS DEVELOPING AND POSSIBLY AT-STORM AREAL COVERAGE IS UNCERTAIN BUT BEST CHANCE OF RAINFALL WILL LIKELY BE NEAR THE SOUTH COAST ALONG THE NORTHERN GRADIENT OF HIGH PWAT AXIS BUT CONVECTION ALSO POSSIBLE FURTHERIN THE INTERIOR WHERE MARGINAL INSTABILITY WILL BE PRESENT OTHERWISE, SNE WILL BE ON THE COOL SIDE OF A STALLED BOUNDARY TOTHE SOUTH WITH EASTERLY FLOW RESULTING IN LOTS OF CLOUDS AND TEMPS IN THE 70S IT WILL BE RATHER HUMID WITH DEWPOINTS CLIMBING TO UPPER 60S AND LOWER 70S
PREVIOUS DISCUSSION
SYNOPTIC PATTERN REMAINS RELATIVELY UNCHANGED FROM TUESDAY WITH BROAD TROUGH CENTERED OVER SOUTHERN ONTARIO/GREAT LAKES AND A STATIONARY BOUNDARY IN THE VICINITY OF SOUTHERN NEW ENGLAND THERE REMAINS CONSIDERABLE MOISTURE IN THE LOWEST LEVELS OF THE COLUMN, WITH PATCHY DRIZZLE PRESENT ACROSS PORTIONS OF INTERIOR SOUTHERN NEW ENGLAND THIS MORNING
SHORTWAVE REMAINS ON TRACK TO EJECT OFF THE MID-ATLANTIC COAST, WITH THE NORTHERN FRINGES OF THE PRECIPITATION SHIELD NOW VISIBLE ON OUR RADAR SKIRTING THE SOUTH COAST OF LONG ISLAND; THOUGH REMAINING SOUTH OF THE ISLANDS FOR NOW OVERNIGHT GUIDANCE REMAINS A BIT INCONSISTENT WITH THE POSITION OF THE BOUNDARY AND THE NORTHERN EXTENT OF THE PRECIPITATION SHIELD, WHICH INTRODUCES UNCERTAINTY IN WHO WILL ACTUALLY SEE SHOWER ACTIVITY TODAY GENERAL THINKING IS THAT THE BEST CHANCE FOR SCATTERED SHOWERS THIS MORNING WILL OCCUR SE OF I-95, WITH SCATTERED SHOWERS DEVELOPING BETWEEN 17-21Z FOR PORTIONS OF THE INTERIOR AHEAD OF AN APPROACHING COLD FRONT
DID TREND THE FORECAST IN A DRIER DIRECTION TODAY GIVEN THE TENDENCY FOR GUIDANCE TO OVERESTIMATE THE NORTHERN EXTENT OF THE BOUNDARY OVER THE LAST SEVERAL FORECAST CYCLES IN LIGHT OF PWAT'S IN EXCESS OF 2" ALONG THE SOUTH COAST AND WARM CLOUD DEPTHS OVER 12-14K FT, THE THREAT FOR HEAVY RAIN HAS SHIFTED OFF THE COAST, WITH HREF 6HR PMM SHOWING LOCALIZED MAXIMA OF JUST 025" ACROSS THE ISLANDS THROUGH 18Z, PRETTY MUCH ELIMINATING THE CHANCE FOR URBAN/POOR DRAINAGE FLOODING TODAY IN SUM, TODAY WONT BE A WASHOUT FOR ANY PARTICULAR LOCATION
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/* THREAT FOR ISOLATED DOWNPOURS AND THUNDERSTORMS OVERNIGHT TONIGHT FOR WESTERN MA/NORTHERN CT BETWEEN ~03-07Z AHEAD OF APPROACHING COLD FRONT
* DECREASING POTENTIAL FOR ISOLATED SEVERE STORMS ON THURSDAY; POTENTIAL FOR A "SHUTOUT" THANKS TO STABILIZING CLOUD COVER
TONIGHT
TROUGH SHIFTS EAST TONIGHT ALONG WITH A COLD FRONT THAT WILL BRING THE CHANCE FOR SCATTERED DOWNPOURS AND PERHAPS A RUMBLE OF THUNDER TONIGHT TO THE WESTERN HALF OF OUR CWA OVERALL, IT APPEARS THAT THE MOST WIDESPREAD SHOWERS AND ISOLATED STORMS WILL OCCUR LATE TONIGHT, BETWEEN 03-07Z WITH RESIDUAL HEALTHY PWATS AND DEEP WARM CLOUD DEPTHS, COULD SEE LOCALIZED DOWNPOURS CAPABLE OF DROPPING A QUICK HALF INCH OF RAIN ACROSS WESTERN MA, THOUGH THE PROSPECT OF RAIN EAST OF THE CONNECTICUT RIVER VALLEY LOOKS DISMAL GIVEN THE VERY ISOLATED RISK FOR LOCALIZED DOWNPOURS, DID NOT CONSIDER ISSUING A FLOOD WATCH FOR ANY PORTION OF THE REGION
PATCHY FOG LOOKS LIKELY TONIGHT, ESPECIALLY ALONG THE COAST, AS WINDS SHIFT MORE SOUTHERLY OVERNIGHT
THURSDAY
IN CONTRAST TO PREVIOUS UPDATES, THE RISK FOR WIDELY SCATTERED THUNDERSTORMS HAS DECREASED TOMORROW, WITH MOST IF NOT ALL HREF MEMBERS TRENDING TOWARDS A SHUTOUT DURING THE DAYLIGHT HOURS OF THURSDAY WHILE THERE APPEARS TO BE AMPLE FORCING WITH THE APPROACHING FRONT/HEIGHT FALLS AND MODEST INSTABILITY OF NEAR 1000J/KG, MID LEVEL LAPSE RATES ARE QUITE POOR, AROUND 5C/KM IN ADDITION TO POOR LAPSE RATES, EXPECTING IT TO BE QUITE CLOUDY FOR THE BETTER PART OF THE DAYLIGHT HOURS UNTIL THE FRONT LEADS TO RAPID CLEARING TOMORROW EVENING, WHICH WILL INHIBIT DESTABILIZATION AND STORM DEVELOPMENT GIVEN CONFLICTING SIGNALS, DO ESTIMATE THAT GUIDANCE LIKE THE HRRR, WHICH ESSENTIALLY SHOWS A SHUT OUT TOMORROW, IS A BIT TOO CONSERVATIVE IN SHOWER AND STORM COVERAGE, HAVE AGAIN TRENDED THE FORECAST DRIER FOR THE PERIOD SHOWERS LOOK TO BE WIDELY SCATTERED TO ISOLATED WITH PERHAPS A FEW EMBEDDED THUNDERSTORMS IF CLEARING OCCURS EARLIER THAN FORECAST OVERALL, THINK THE SEVERE THREAT IS RATHER LOW, BUT CAN'T RULE OUT ISOLATED STORMS CAPABLE OF GUSTY WINDS; CORROBORATED BY THE CSU MACHINE LEARNING PROBS SHOWING A 5% RISKOF DAMAGING WINDS SPC CONTINUES TO MAINTAIN A "GENERAL THUNDER" RISK FOR OUR REGION, ATTRIBUTING THE LACK OF SEVERE POTENTIAL TO THE AFOREMENTIONED CLOUD COVER WILL NOTE THAT THEGFS REMAINS THE "WET" OUTLIER FOR THURSDAY, MAINTAINING IT'S ESTIMATE OF MORE WIDESPREAD SCATTERED SHOWERS AND THUNDERSTORMS
LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/KEY POINTS
* DRY AND SEASONABLE CONDITIONS FRI WITH A WARMING TREND THIS WEEKEND* HEAT AND HUMIDITY BUILDS EARLY NEXT WEEK
THURSDAY NIGHT AND FRIDAY
COLD FRONT NEAR THE COASTAL PLAIN THU EVENING WILL MOVE OFF THE COAST BY MIDNIGHT LOW RISK FOR A FEW SHOWERS AND PERHAPS A T-STORM NEAR THE SOUTH COAST IN THE EVENING WITHIN THE MOISTURE AXIS AHEAD OF THE FRONT, THEN A DRYING TREND WILL TAKE PLACE OVERNIGHT WITH CLEARING SKIES AND DECREASING HUMIDITY AS THE FRONT MOVES OFFSHORE
POST-FRONTAL AIRMASS ON FRIDAY WITH SEASONABLE TEMPS AND SCT-BKN DIURNAL CU DEVELOPING OVERALL A MOSTLY SUNNY DAY WITH SEASONABLE TEMPS 80-85 AND NEAR NORMAL HUMIDITY FOR LATE JULY WITH DEWPOINTS UPPER 50S AND LOWER 60S
SATURDAY THROUGH TUESDAY
AN EXTENDED PERIOD OF MAINLY DRY WEATHER IS ANTICIPATED THIS WEEKEND INTO EARLY NEXT WEEK AS HIGH PRES TAKES CONTROL HOWEVER, WILL HAVE TO WATCH A WEAKNESS IN THE UPPER FLOW OFF THE NEW ENG COAST DOWNSTREAM OF THE BUILDING RIDGE SUN AND MON LATEST ENSEMBLE GUIDANCE IS OVERWHELMINGLY DRY DURING THIS TIME SO WILL MAINTAIN A DRY FORECAST FORECAST CONFIDENCE DECREASES TUE DUE TO TIMING UNCERTAINTY WITH NEXT APPROACHING SHORTWAVE AND ASSOCD MOISTURE INCREASE MAJORITY OF ENSEMBLES KEEP IT DRY TUE FOR NOW
WARMING TEMPS SAT AND SUNDAY WELL INTO THE 80S BUT WITH MANAGEABLE HUMIDITY, THEN THERE IS A SIGNAL FOR INCREASING HEAT AND HUMIDITY EARLY NEXT WEEK, ESPECIALLY AWAY FROM THE COAST AS TEMPS ALOFT WARM HOWEVER, THE UPPER LEVEL LOW JUST OFFSHORE SUN-MON MAY LEAD TO ONSHORE FLOW AND SOMEWHAT COOLER TEMPS ALONG THE COAST
AVIATION /12Z WEDNESDAY THROUGH SUNDAY/FORECAST CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENTMODERATE - 30 TO 60 PERCENTHIGH - GREATER THAN 60 PERCENT
12Z TAF UPDATE:
TODAY MODERATE CONFIDENCE
MAINLY MVFR-IFR CIGS WILL PERSIST TODAY, POSSIBLY IMPROVING TO A BRIEF PERIOD OF VFR IN THE CT VALLEY BUT IFR EXPECTED TODOMINATE IN EASTERN MA LATER IN THE AFTERNOON SCATTEREDSHOWERS
TONIGHT MODERATE CONFIDENCE
MVFR/IFR LIKELY WITH NE/N WINDS SCATTERED SHOWERS WILL COME TOAN END QUICKLY AFTER SUNSET BUT CANT RULE OUT SOME LINGERINGDRIZZLE FOG DEVELOPMENT VERY LIKELY, ESPECIALLY ALONG THE SOUTHCOAST AND ACROSS THE ISLANDS
THURSDAY MODERATE CONFIDENCE EARLY MORNING IFR/LIFR WILLLIFT TO VFR BY MID MORNING COLD FRONTAL PASSAGE LATER THURSDAYWILL LEAD TO A WIND SHIFT WITH SCATTERED TSRA CONFIDENCE IS LOWIN TSRA REACHING THE COASTLINE
KBOS TAF MODERATE CONFIDENCE IN TAF
VARIABLE CIGS TRENDING TO MVFR-IFR UNCERTAINTY REGARDING A BRIEF WINDOW OF IMPROVEMENT TO VFR AROUND 16Z THIS MORNING, THOUGH WITH E/ENE WINDS WILL BE TOUGH TO SUSTAIN LONG TERM IMPROVEMENT AT THE TERMINAL IFR REDEVELOPS THIS EVENING SHOWERACTIVITY LIKELY STAYS TO THE SE OF THE TERMINAL BUT THE BEST CHANCE FOR RUNWAY- WETTING RAIN COMES BETWEEN ~17-21Z THIS AFTERNOON
KBDL TAF MODERATE CONFIDENCE IN TAF MVFR TO IFR THIS MORNINGWITH IMPROVEMENT TO VFR LATE MORNING AND EARLY AFTERNOON WILLSEE CONDITIONS DETERIORATE TO IFR AGAIN OVERNIGHT WITH FOGDEVELOPMENT LIKELY SHOWERS POSSIBLE LATE THIS AFTERNOON BUT THESTEADIEST RAIN WILL STAY WELL SOUTH OF THE TERMINAL
OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/
VFR
MARINEFORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENTMEDIUM - 30 TO 60 PERCENTHIGH - GREATER THAN 60 PERCENT
THROUGH TONIGHT HIGH CONFIDENCE
STATIONARY BOUNDARY DRAPED ACROSS THE SOUTHERN WATERS WILL PROVIDE A SOURCE FOR SHOWER AND STORMS TODAY ALONG WITH PERIODS OF POOR VISIBILITY WINDS FROM THE ESE TO SE WITH SPEEDS 10 TO 15 KNOTSAND SEAS BETWEEN 2 AND 4 FEET WIND SHIFT OCCURS LATE WEDNESDAYEVENING INTO THURSDAY MORNING AS A WEAK FRONT MOVES ACROSS THE WATERS, WIND SHIFT FROM SE TO SW, WIND SPEEDS LESS THAN 10 KNOTSWITH SEAS 3 TO 4 FEET
TOMORROW HIGH CONFIDENCE
MARINE FOG/STRATUS WILL LINGER FOR A GOOD PORTION OF THURSDAYMORNING WITH MORE SOUTHERLY WINDS ISOLATED SHOWER ORTHUNDERSTORM POSSIBLE ALONG A COLD FRONT, WITH RAPID CLEARINGEXPECTED BEHIND THE FRONT AS WINDS SHIFT MORE TO THE WEST SEASREMAIN BELOW SCA CRITERIA BETWEEN 2-4FT
OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/
THURSDAY NIGHT: WINDS LESS THAN 25 KT AREAS OF SEASAPPROACHING 5 FT SLIGHT CHANCE OF RAIN SHOWERS, ISOLATEDTHUNDERSTORMS
FRIDAY THROUGH SUNDAY: WINDS LESS THAN 25 KT
BOX WATCHES/WARNINGS/ADVISORIESCTNONEMANONERINONEMARINENONE
SYNOPSISKJC/KSNEAR TERMKJC/KSSHORT TERMKSLONG TERMKJCAVIATIONKJC/KSMARINEKJC/KS
