886
FXUS61 KBOX 251920
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
320 PM EDT TUE MAR 25 2025
SYNOPSIS
LOW PRESSURE TRACKING SOUTH AND EAST OF NEW ENGLAND MAY BRING A
PERIOD OF RAIN TO THE CAPE/ISLANDS LATE TONIGHT INTO WEDNESDAY
MORNING. ANOTHER FAST MOVING DISTURBANCE MAY BRING A FEW SHOWERS
WEDNESDAY AFTERNOON AND EARLY EVENING WITH SNOW SHOWERS OVER HIGHER
ELEVATIONS. DRY AND SEASONABLE WEATHER RETURNS FOR THURSDAY.
ALTHOUGH WE DO GET A MAINLY DRY COLD FRONTAL PASSAGE FOR THURSDAY
NIGHT, BLUSTERY AND DRY WEATHER IS EXPECTED FOR LATE IN THE
WORKWEEK. AN OVERCAST AND MORE UNSETTLED WEATHER PATTERN THEN
DEVELOPS THIS WEEKEND WITH A QUASI-STATIONARY FRONTAL BOUNDARY NEAR
SOUTHERN NEW ENGLAND, WHICH WOULD BRING EITHER PERIODS OF LIGHT RAIN
AND/OR A WINTRY MIX. IT REMAINS ACTIVE INTO EARLY NEXT WEEK, WITH
MILD SOUTHERLY FLOW ALLOWING FOR PERIODS OF RAIN TO DEVELOP.
NEAR TERM /THROUGH WEDNESDAY/
KEY MESSAGES:
* A PERIOD OF LIGHT RAIN POSSIBLE ACROSS CAPE/ISLANDS LATE TONIGHT
AND WED MORNING.
* WIDELY SCATTERED SHOWERS DEVELOPING WED AFTERNOON
TONIGHT AND WEDNESDAY...
UPPER LOW SLIDES EAST FROM THE GT LAKES TONIGHT WITH SHORTWAVE
ENERGY ROUNDING THE BASE OF THE TROUGH RESULTING IN COASTAL LOW
MOVING OFF THE MID ATLC COAST. CONSENSUS OF THE GUIDANCE FAVORS AN
OFFSHORE TRACK SOUTH AND EAST OF THE BENCHMARK, BUT SOME DIFFERENCES
IN THE NW EXTENT OF THE QPF. GFS REMAINS ON THE SE ENVELOPE OF
SOLUTIONS WITH PRECIP REMAINING OFFSHORE. BUT ECMWF AND RGEM BRING
QPF ACROSS SE NEW ENG LATE TONIGHT INTO WED MORNING AND HREF HI-RES
MEMBERSHIP HAS ALSO TRENDING NW WITH QPF. ECMWF ENSEMBLES RATHER
BULLISH ON RAIN ACROSS SE NEW ENG WITH 60-80% PROBS OF QPF > 0.10"
OVER CAPE/ISLANDS. AND THERE ARE SEVERAL GEFS MEMBERS WITH AT LEAST
0.01" ACROSS SE NEW ENG WHICH IS FURTHER NW THAN DETERMINISTIC RUN.
THE KEY TO THE FORECAST IS THE POTENTIAL FOR AN INVERTED TROUGH TO
DEVELOP IN RESPONSE TO STRONG UPSTREAM UPPER TROUGH WHICH MAY BE
ENOUGH TO GET SOME RAIN EXPANDING ACROSS CAPE/ISLANDS LATE TONIGHT
AND WED MORNING, AND POSSIBLY AS FAR NW AS PORTIONS OF SE MA AND
COASTAL RI. WE TRENDED POPS HIGHER WITH CHANCE ALONG THE SOUTH COAST
INCREASING TO LIKELY OVER NANTUCKET. WHILE 850 MB TEMPS ARE FAIRLY
COLD, SURFACE TEMPS WILL BE IN THE MID-UPPER 30S SO EXPECT PTYPE TO
BE ALL RAIN, WITH POSSIBLY A BRIEF MIX WITH SNOW IF PRECIP GETS
FURTHER NW INTO SE MA.
RAIN WILL EXIT THE OUTER CAPE/ISLANDS BY LATE MORNING OR MIDDAY WED.
UPPER LOW AND IMPRESSIVE COLD POOL ALOFT MOVE INTO NEW ENG DURING
THE AFTERNOON WITH 500 MB TEMPS DROPPING TO -36C. ANY MORNING SUN
AWAY FROM THE COAST WILL GIVE WAY TO INCREASING STRATO-CU. WE WILL
HAVE A DEEP AND VERY WELL MIXED BOUNDARY LAYER INTO THE MID LEVELS
WITH 0-3KM LAPSE RATES APPROACHING DRY ADIABATIC WHICH WILL LIKELY
LEAD TO SOME CONVECTIVE SHOWERS DEVELOPING ACROSS SNE IN THE
AFTERNOON. SHOWERS MAY BE IN THE FORM OF SNOW SHOWERS OVER HIGHER
ELEVATIONS AND MAY CONTAIN SOME GRAUPEL. DESPITE DEEP BOUNDARY
LAYER, NOT A LOT OF WIND ALOFT WITH SOUNDINGS SHOWING POTENTIAL FOR
20 MPH GUSTS. HIGHS WED WILL BE MOSTLY IN THE 40S TO AROUND 50 IN
THE COASTAL PLAIN, BUT TEMPS WILL FALL INTO THE 30S TO LOWER 40S
WITH ANY SHOWERS.
SHORT TERM /WEDNESDAY NIGHT/
UPPER LOW EXITS TO THE EAST DURING THE EVENING FOLLOWED BY RISING
HEIGHTS. A FEW SHOWERS MAY LINGER ACROSS SE MA AND CAPE/ISLANDS IN
THE EVENING, OTHERWISE TREND WILL BE FOR CLEARING SKIES AS DRIER AIR
MOVES INTO THE REGION. DECENT PRESSURE GRADIENT ACROSS THE REGION
WILL KEEP WINDS STRONG ENOUGH (NW 5-15 MPH) TO LIMIT RADIATIONAL
COOLING. LOWS WILL DROP INTO THE MID-UPPER 20S INTERIOR AND LOWER
30S NEAR THE COAST.
LONG TERM /THURSDAY THROUGH TUESDAY/
KEY MESSAGES:
* BLUSTERY AND DRY WITH LOWER RELATIVE HUMIDITIES THU-FRI
* OVERCAST AND UNSETTLED PATTERN THIS WEEKEND WITH A WAVY FRONTAL
BOUNDARY NEAR OR OVER SOUTHERN NEW ENGLAND, BUT LOW CONFIDENCE ON
TEMPERATURES AND PRECIP TYPE DETAILS. STEADY LIGHT RAIN/DRIZZLE
FOR ALL AND/OR A RAIN-TO-WINTRY-MIX BOTH ON THE TABLE BUT THESE
WILL HINGE ON SURFACE TEMPERATURES.
* REMAINS ACTIVE INTO EARLY NEXT WEEK, WITH OVERCAST BUT MILD ENOUGH
FOR PLAIN RAIN.
DETAILS:
THURSDAY AND FRIDAY:
HIGH PRESSURE AT SURFACE ON THURS WITH RATHER COLD POCKET OF AIR
ALOFT WILL FAVOR MOSTLY SUNNY, DRY AND BREEZY CONDITIONS WITH
DEWPOINTS EXPECTED TO MIX OUT DURING THE DAYTIME HRS. WESTERLY
BREEZES AROUND 20-25 MPH DURING THE DAYTIME AND WITH TEMPS IN THE
UPPER 40S TO LOW 50S, RHS MAY TUMBLE INTO THE MID 20S IN THE
INTERIOR TO THE 30-35 PERCENT RANGE FOR THE COASTS.
ANOTHER PASSING SURFACE COLD FRONT THEN MOVES IN FOR THURS NIGHT
INTO EARLY ON FRI. THE PRECEDING AIRMASS IS RATHER DRY AND THE
COARSER-RES MODEL QPF AT THIS TIME RANGE IS PRETTY SPARSE. WOULDN'T
RULE OUT A PASSING SHOWER BUT IT MAY BE TOO DRY TO SUPPORT ANY
PRECIP, ALTHOUGH A PERIOD OF ENHANCED CLOUD COVER SEEMS TO BE A GOOD
BET. RATHER CHILLY LOWS IN THE UPPER 20S TO THE MID 30S WITH NW
WINDS KICKING UP BEHIND THE COLD FRONT BY EARLY FRI AM.
FOR FRI...HIGH PRESSURE AGAIN REBUILDS BACK INTO THE REGION,
ALTHOUGH WITH BLUSTERY TO GUSTY NORTHWEST WINDS AND AGAIN GOOD
MIXING OF GUSTS AND LOWER DEWPOINTS TO THE SURFACE. WITH
TEMPERATURES IN THE 50S, MAY AGAIN SEE RHS FALL INTO THE 25 TO 35
PERCENT RANGE DURING THE DAYTIME HOURS. THUS, BOTH DAYS LATE IN THE
WEEK COULD BE ONES WHICH COULD HAVE SOME FIRE WEATHER CONCERNS GIVEN
THE COMBO OF LOWER RHS AND GUSTY CONDITIONS.
THE WEEKEND:
RATHER ACTIVE WEATHER PATTERN SHAPING UP FOR SOUTHERN NEW ENGLAND IN
THIS FORECAST PERIOD AS A WAVY FRONTAL BOUNDARY WITH AN ASSOCIATED
WEST TO EAST SHARP THERMAL BOUNDARY DRAPED IN THE VICINITY OF
SOUTHERN NEW ENGLAND. A MUCH COLDER AIRMASS RESIDES TO THE NORTH OF
THIS FRONTAL BOUNDARY, WHILE THE AIRMASS SOUTH OF IT LOOKS TO BE
QUITE WARM. ALTHOUGH REASONABLE CONFIDENCE EXISTS ON PERSISTENT
OVERCAST CONDITIONS THIS WEEKEND AS AT LEAST SHALLOW MOISTURE IS
LIKELY TO BE TRAPPED UNDERNEATH A STRONG THERMAL INVERSION, DETAILS
REGARDING POPS AS WELL AS THE LOW-LEVEL THERMAL STRUCTURE AND
SURFACE TEMPS IS LOW CONFIDENCE AND HIGHLY UNCERTAIN. THIS
UNCERTAINTY LENDS ITSELF TO POTENTIAL HIGH/LOW TEMPERATURE BUSTS AND
MULTIPLE POTENTIAL WEATHER SCENARIOS RANGING FROM A MILD RAIN AND/OR
DRIZZLE THROUGHOUT, TO A LONGER-DURATION RAIN TO WINTRY MIXED PRECIP
EVENT FOR SOME IN SOUTHERN NEW ENGLAND, OR SOMETHING IN BETWEEN.
THESE DETAILS WILL HINGE GREATLY ON SURFACE TEMPS. THIS UNCERTAINTY
IS BEST SEEN IN THE SPREAD BETWEEN THE NBM 10TH AND 90TH PERCENTILE
TEMPERATURES PARTICULARLY FOR SATURDAY NIGHT FOR LOCATIONS NORTH OF
THE MASS PIKE, WHICH RANGE FROM 10TH-PERCENTILE VALUES IN THE LOW
30S TO 90TH PERCENTILE VALUES IN THE MID 50S!
APPROACH FOR THIS FORECAST WAS TO LEAN SOMEWHAT COOLER AND TOWARD
LESS OF A LARGER DIURNAL RANGE THAN NBM SHOWS ON TEMPS, ALTHOUGH NOT
AS COLD AS SOME OF THE COLDEST GUIDANCE, WITH POPS IN THE HIGH
CHANCE TO LIKELY RANGE. THIS SHOWS MOSTLY LIGHT RAIN TO START ON
SAT, THEN INTRODUCES MORE OF A SNOW/RAIN MIX (WHICH COULD BE MORE IN
THE FORM OF TYPES OTHER THAN SNOW OR RAIN) NEAR AND NORTH OF I-90
FOR SAT NIGHT, BEFORE GRADUALLY MODIFYING TO PLAIN RAIN IN ALL AREAS
FOR SUN. THIS SOLUTION AT LEAST HINTS AT THE POTENTIAL FOR TEMPS
COLD ENOUGH FOR SOME WINTRY WEATHER, ALTHOUGH TODAY'S 12Z GUIDANCE
DID SHOW MORE MILDER AIR INTO SOUTHERN NEW ENGLAND THAN PREVIOUS
RUNS. ULTIMATELY DETAILS ON SURFACE TEMPERATURES WILL DICTATE WHAT
PRECIP TYPES WE DO SEE, AND THAT'S CURRENTLY TOO UNCERTAIN TO LOCK
IN AT THIS POINT IN TIME.
EARLY NEXT WEEK:
REMAINS UNSETTLED AS SLOW-MOVING FRONTAL SYSTEM OVER THE GREAT
PLAINS MOVES EASTWARD THROUGH THE NORTHEAST STATES. ALTHOUGH A MILD
SOUTHWESTERLY FLOW / WARM SECTOR AIRMASS BUILDS OVER SOUTHERN NEW
ENGLAND, LOOKS MOSTLY CLOUDY TO OVERCAST WITH PERIODS OF RAIN (POPS
HIGH CHANCE TO LIKELY).
AVIATION /19Z TUESDAY THROUGH SUNDAY/
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THROUGH 00Z...
VFR WITH SCT-BKN CIGS 5-6 KFT. W WIND GUSTS TO 25 KT.
TONIGHT AND WEDNESDAY...HIGH CONFIDENCE.
MAINLY VFR. LOWERING CIGS AROUND 5K FT TOWARD CAPE/ISLANDS LATE
TONIGHT AND WED MORNING WITH INCREASING RISK FOR A PERIOD OF
LIGHT RAIN. BRIEF LOWER CONDITIONS TO MVFR POSSIBLE. SCT-BKN
CIGS AROUND 5K FT DEVELOPING IN THE AFTERNOON ACROSS SNE WITH A
FEW SHOWERS POSSIBLE. W WIND 8-10 KT WITH G15-20 KT POSSIBLE.
WEDNESDAY NIGHT...HIGH CONFIDENCE.
VFR. NW WIND 5-15 KT.
BOS TAF...HIGH CONFIDENCE.
BDL TAF...HIGH CONFIDENCE.
OUTLOOK /THURSDAY THROUGH SUNDAY/...
THURSDAY THROUGH FRIDAY: VFR. BREEZY.
FRIDAY NIGHT: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. CHANCE RA.
SATURDAY: MAINLY VFR, WITH AREAS MVFR POSSIBLE. CHANCE RA.
SATURDAY NIGHT: MVFR/IFR CONDITIONS POSSIBLE. CHANCE RA, SN
LIKELY.
SUNDAY: MAINLY IFR, WITH AREAS MVFR POSSIBLE. BREEZY. RA
LIKELY.
MARINE
FORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
TONIGHT THROUGH WEDNESDAY NIGHT: HIGH CONFIDENCE.
DIMINISHING WINDS THIS EVENING WITH SEAS SUBSIDING BELOW 5 FT. W-SW
WIND 10-15 KT WED SHIFTING TO NW 15-20 KT WED NIGHT WITH SEAS
REMAINING BELOW SCA. A PERIOD OF RAIN IS LIKELY ACROSS SOUTHERN AND
SE WATERS LATE TONIGHT AND WED MORNING.
OUTLOOK /THURSDAY THROUGH SUNDAY/...
THURSDAY THROUGH THURSDAY NIGHT: WINDS LESS THAN 25 KT. AREAS
OF SEAS APPROACHING 5 FT.
FRIDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS UP
TO 25 KT. AREAS OF SEAS APPROACHING 5 FT.
FRIDAY NIGHT: WINDS LESS THAN 25 KT. CHANCE OF RAIN.
SATURDAY THROUGH SATURDAY NIGHT: WINDS LESS THAN 25 KT. AREAS
OF SEAS APPROACHING 5 FT. CHANCE OF RAIN.
SUNDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. CHANCE OF RAIN.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR
ANZ230>234-236-251.
SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ235-
237.
SMALL CRAFT ADVISORY UNTIL 4 AM EDT WEDNESDAY FOR ANZ254>256.
SYNOPSIS...KJC/LOCONTO
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...LOCONTO
AVIATION...KJC/LOCONTO
MARINE...KJC/LOCONTO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page