339
FXUS61 KBOX 071829
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
229 PM EDT TUE JUL 7 2020
SYNOPSIS
A FRONTAL BOUNDARY SOUTH OF OUR REGION WILL RESULT IN DRY AND
COMFORTABLE WEATHER TODAY. THIS FRONT LIFTS NORTH OF OUR REGION
TONIGHT WITH A FEW SHOWERS, BUT ITS MAIN IMPACT WILL BE TO DELIVER
SUMMERLIKE WARMTH AND HUMIDITY THE REST OF THE WEEK INTO THE
WEEKEND. SHOWERS/THUNDERSTORMS WILL BE POSSIBLE EACH DAY WITH SOME HEAVY
DOWNPOURS, BUT MUCH OF THIS TIME WILL ALSO FEATURE DRY WEATHER.
A STRONGER SYSTEM LATE FRIDAY INTO SATURDAY BRINGS HEAVY RAIN
AND POTENTIAL FLOODING ISSUES.
NEAR TERM /UNTIL 8 PM THIS EVENING/
215 PM UPDATE...
GORGEOUS DAY FOR EASTERN MA INTO MUCH OF RI (ALTHOUGH LOW CLOUDS
IMPACTING RI BEACHES) WITH SUNSHINE THRU HIGH CLOUDS, TEMPS
75-80 ALONG WITH COMFORTABLE HUMIDITY AS DEW PTS RANGE FROM
55-60. HOWEVER FARTHER TO THE WEST ACROSS CT INTO WESTERN-
CENTRAL MA, STRATO-CU PERSISTING AND RESULTING IN MAINLY
OVERCAST CONDITIONS, ALTHOUGH TEMPS HAVE CLIMBED INTO THE MID TO
UPPER 70S. FEELS WARM TOO WITH DEW PTS IN THE CT RIVER VALLEY IN
THE LOW TO MID 60S.
NOT EXPECTING ANY PRECIP THRU SUNSET AS WAA PATTERN IS VERY WEAK
WITH 925 AND 850 MB WINDS FAIRLY LIGHT. THUS PLEASANT WEATHER
INTO THIS EVENING, HOWEVER LOW CLOUDS OVER THE RI COASTAL WATERS
WILL BEING TO ADVANCE ONSHORE AS BOUNDARY LAYER COOLS TOWARD
SUNSET. S-SE WINDS WILL REMAIN FAIRLY LIGHT AND DEW PTS WILL
REMAIN IN THE UPPER 50S TO LOWER 60S EXCEPT MID 60S ACROSS CT
INTO WESTERN-CENTRAL MA.
SHORT TERM /8 PM THIS EVENING THROUGH 6 PM WEDNESDAY/
* A FEW STRONG TO SEVERE THUNDERSTORMS WITH HEAVY RAIN POSSIBLE
WEDNESDAY AFTERNOON/EVENING ACROSS WESTERN & NORTHERN MA
TONIGHT...
THE HIGH PRESSURE SYSTEM MOVES SOUTHEAST OF THE CANADIAN MARITIMES
TONIGHT. THIS WILL ALLOW A RETURN SOUTHERLY FLOW OF INCREASING LOW
LEVEL MOISTURE. THERE WILL BE AN INCREASE IN ELEVATED INSTABILITY
AND WITH JUST ENOUGH OF A SOUTHERLY LLJ A FEW SHOWERS WITH PERHAPS A
RUMBLE OR TWO OF THUNDER WILL BE POSSIBLE. CERTAINLY NOT A WASHOUT,
BUT THE RISK EXISTS FOR A FEW SHOWERS PARTICULARLY AFTER MIDNIGHT.
WE SHOULD ALSO SEE LOW CLOUDS AND SOME PATCHES OF FOG DEVELOP
TONIGHT WITH THE INCREASING LOW LEVEL MOISTURE. OVERNIGHT LOW TEMPS
SHOULD ONLY DROP INTO THE MIDDLE TO UPPER 60S.
WEDNESDAY...
IT WILL BE WARM ON WEDNESDAY, BUT MORE IMPORTANTLY BECOME RATHER
HUMID WITH DEWPOINTS NEAR 70. AFTERNOON HIGH TEMPS SHOULD REACH INTO
THE 80S, BUT HEAT INDICES WILL REACH THE LOWER 90S IN SOME
LOCATIONS.
WE MAY SEE A FEW SHOWERS WEDNESDAY MORNING IN THE WARM ADVECTION
PATTERN, BUT NOT EXPECTING A WASHOUT. THE BIGGER CONCERN WILL BE
FROM WEDNESDAY AFTERNOON AND EVENING ACROSS WESTERN AND NORTHERN MA.
GIVEN THE HIGH DEWPOINTS IN PLACE, WE SHOULD SEE 1500 TO 2500 J/KG
OF CAPE DEVELOP. A SHORTWAVE WILL ALSO BE DROPPING DOWN IN NORTHWEST
FLOW ALOFT, WHICH WILL TRIGGER SCATTERED SHOWERS AND THUNDERSTORMS
ACROSS NORTHERN NEW ENGLAND. THE BETTER EFFECTIVE BULK SHEAR AND
HIGHER UPDRAFT HELICITY VALUES COURTESY OF THE HREF MODEL ARE TO THE
NORTH OF OUR REGION. THIS IS WHERE THE HIGHEST RISK FOR STRONG TO
SEVERE THUNDERSTORMS EXIST.
THAT BEING SAID, WESTERN AND NORTHERN MA ARE CERTAINLY NOT OUT OF
THE WOODS. EFFECTIVE SHEAR OF 25 KNOTS AND CAPES POTENTIALLY
EXCEEDING 2000 J/KG IS CERTAINLY ENOUGH FOR A FEW STRONG TO SEVERE
WEDNESDAY AFTERNOON AND EVENING ACROSS WESTERN AND NORTHERN MA. MAIN
RISK WOULD BE LOCALIZED STRONG TO DAMAGING WIND GUSTS. IN ADDITION,
PWATS APPROACHING 2 INCHES WOULD RESULT IN A HEAVY RAIN/LOCALIZED
STREET FLOODING THREAT WITH THE STRONGEST STORMS. WE WILL HAVE TO
EXAMINE THE TRENDS OF THE HIGH RESOLUTION CAMS AS THERE IS SOME
UNCERTAINTY ON TIMING AND HOW FAR SOUTH THIS THREAT WILL GET.
NONETHELESS, IT CERTAINLY WILL NEED TO BE MONITORED.
LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/
HIGHLIGHTS...
* HOT AND HUMID CONDITIONS CONTINUE
* SCATTERED SHOWERS AND THUNDERSTORMS ON THURSDAY
* WIDESPREAD, HEAVY RAIN FRIDAY INTO SATURDAY
DETAILS...
A WEAK HIGH PRESSURE RIDGE KEEPS THE HOT AND HUMID AIRMASS IN PLACE
ON THURSDAY AHEAD OF A DEEPER SHORTWAVE AND CLOSED UPPER LOW OFF THE
COAST OF THE CAROLINAS WHICH WILL BRING WIDESPREAD HEAVY RAIN FRIDAY
INTO SATURDAY. ALOFT THE MID LEVEL TROUGH LAGS BEHIND THE COASTAL
LOW, KEEPING SHOWER AND THUNDERSTORM CHANCES IN THE FORECAST THROUGH
AT LEAST THE WEEKEND.
THURSDAY SOUTHERLY FLOW AROUND THE OFFSHORE HIGH KEEPS TEMPERATURES
ABOVE NORMAL (IN THE UPPER 80S TO NEAR 90) WITH OPPRESSIVE HUMIDITY
(LOW 70S). GIVEN THIS, WE'LL HAVE ENOUGH INSTABILITY AND MOISTURE FOR
SCATTERED SHOWERS AND THUNDERSTORMS, EVEN THOUGH FORCING IS LACKING.
A COLD FRONT MAY COME CLOSE ENOUGH TO HELP BUT LOOKS TO STALL
SOMEWHERE TO OUR NW. WIND FIELDS AREN'T SUPPORTIVE OF VERY ORGANIZED
CONVECTION, BUT CAN'T RULE OUT A STRONG TO SEVERE STORM OR TWO.
EYES THEN TURN TO THE FRIDAY/SATURDAY TIME PERIOD WHERE, IF GUIDANCE
IS ANY INDICATION, SIGNIFICANT RAINFALL IS LIKELY. THIS IS THANKS TO
A COASTAL LOW SLIDING UP FROM THE CAROLINAS, PULLED NORTH AHEAD OF
THE TROUGH DIGGING INTO THE GREAT LAKES. THIS HAS THE POTENTIAL TO
BRING SHOWERS AND THUNDERSTORMS WITH GUSTY WINDS AND VERY HEAVY
DOWNPOURS. CONFIDENCE IN RAINFALL AMOUNTS AND PLACEMENT IS LOW,
DEPENDING HEAVILY ON THE EVENTUAL LOW TRACK. HOWEVER, HEAVY RAINFALL
LOOKS FAIRLY CERTAIN WITH THIS SYSTEM GIVEN A VERY POTENT TAP OF
TROPICAL MOISTURE...PWATS MAY CROSS INTO THE 2.5-3 INCH RANGE! THAT
WOULD BE 2-4 STANDARD DEVIATIONS ABOVE NORMAL FOR MID JULY AND WOULD
LEAD US TO START THINKING ABOUT THE POSSIBILITY OF SOME FLOODING
ISSUES. TEMPERATURES COOL A BIT FROM THURSDAY, INTO THE LOW TO MID
80S.
CONFIDENCE THEN DROPS A GOOD DEAL IN HOW THINGS PLAY OUT. AFTER THIS
SYSTEM IT LOOKS TO STAY UNSETTLED THROUGH EARLY NEXT WEEK. THE
LIKELY SCENARIO IS THAT THE LOW LIFTS OFF INTO THE MARITIMES WHILE
THE MID LEVEL TROUGH AND COLD POOL ALOFT LAG BEHIND, KEEPING SHOWER
AND THUNDERSTORM CHANCES AROUND FOR SUNDAY AHEAD OF YET ANOTHER
DISTURBANCE AROUND MONDAY.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
18Z UPDATE...
THRU 00Z...SOME UNCERTAINTY REGARDING TIMING OF IFR CIGS OVER RI
WATERS COMING ONSHORE THIS EVENING.
VFR AND DRY THRU 00Z. S-SE WINDS REMAIN FAIRLY LIGHT. MVFR/IFR
CIGS OVER THE RI COASTAL WATERS WILL BEGIN TO ADVANCE ONSHORE
AS SUNSET APPROACHES AND TEMPS BEGIN TO COOL. SOME UNCERTAINTY
REGARDING TIMING OF THESE LOW CLOUDS.
AFTER 00Z...MODERATE CONFIDENCE.
TRENDING TOWARD MVFR/IFR AS THE NIGHT PROGRESSES. ISOLATED OR
WIDELY SCATTERED SHOWERS. PROBABILITY OF -TSRA IS VERY LOW.
S-SE WINDS BECOMING S-SW WITH TIME.
WEDNESDAY...MODERATE CONFIDENCE.
MORNING IFR/MVFR IN ISOLATED/SCATTERED SHOWERS GIVES WAY TO
MVFR/VFR CONDITIONS. ISOLATED/SCATTERED TSRA IN THE AFTERNOON
WITH HIGHEST PROBABILITY IS NORTHERN MA, ESPECIALLY WESTERN MA
INTO NW CT. A FEW STRONG STORMS POSSIBLE. SW WINDS 10-15 KT BUT
GUSTS UP TO 20 KT POSSIBLE ESPECIALLY SOUTHEAST MA.
WEDNESDAY NIGHT...MODERATE CONFIDENCE.
ANY EVENING STORMS DIMINISH WITH MAINLY A DRY NIGHT THEREAFTER.
MAINLY VFR BUT LOW PROBABILITY OF MVFR/IFR IN SPOTS. LIGHT SW
WINDS CONTINUE.
KBOS TERMINAL...HIGH CONFIDENCE IN TAF THRU ABOUT 03Z THEN SOME
UNCERTAINTY WHEN AND IF MVFR CIGS ARRIVE ALONG WITH HOW
WIDESPREAD SHOWERS WILL BECOME TONIGHT.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF. SOME UNCERTAINTY IF TSRA
THREAT ACROSS NY/MA/VT/NH WILL EXTEND SOUTHWARD INTO CT.
OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/...
WEDNESDAY NIGHT: VFR. SLIGHT CHANCE SHRA, ISOLATED TSRA.
THURSDAY THROUGH THURSDAY NIGHT: VFR. CHANCE SHRA, SLIGHT
CHANCE TSRA.
FRIDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. BREEZY. CHANCE
SHRA, SLIGHT CHANCE TSRA.
FRIDAY NIGHT: MAINLY VFR, WITH AREAS IFR POSSIBLE. BREEZY. SHRA
LIKELY, SLIGHT CHANCE TSRA.
SATURDAY: MAINLY VFR, WITH LOCAL IFR POSSIBLE. BREEZY. CHANCE
SHRA, ISOLATED TSRA.
MARINE
TODAY THROUGH WEDNESDAY...HIGH CONFIDENCE.
HIGH PRESSURE OVER THE CANADIAN MARITIMES TODAY WILL SHIFT FURTHER
SOUTHEAST THROUGH WEDNESDAY. THE RESULT WILL BE SE WINDS OF 10 TO 15
KNOTS SHIFTING TO THE SW ON WEDNESDAY. GUSTS TO AROUND 20 KNOTS ARE
POSSIBLE THIS AFTERNOON AND PERHAPS SOME NEARSHORE 20 TO 25 KNOT
GUSTS WED AFTERNOON. THIS MAY RESULT IN SOME CHOPPY SEAS, BUT
BIGGEST CONCERN WILL BE THE RISK FOR A FEW STRONG T-STORMS WED
AFTERNOON AND EVENING ACROSS OUR EASTERN MA WATERS. SOME PATCHY FOG
IS EXPECTED ACROSS THE SOUTHERN WATERS EARLY THIS MORNING AND
PARTICULARLY OVERNIGHT INTO WEDNESDAY MORNING.
OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/...
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY
APPROACHING 5 FT. SLIGHT CHANCE OF RAIN SHOWERS, ISOLATED
THUNDERSTORMS.
THURSDAY: WINDS LESS THAN 25 KT.
THURSDAY NIGHT: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN
SHOWERS, ISOLATED THUNDERSTORMS.
FRIDAY: WINDS LESS THAN 25 KT. LOCAL ROUGH SEAS. RAIN SHOWERS
LIKELY, SLIGHT CHANCE OF THUNDERSTORMS.
FRIDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF ROUGH SEAS. RAIN
SHOWERS LIKELY, SLIGHT CHANCE OF THUNDERSTORMS.
SATURDAY: WINDS LESS THAN 25 KT. AREAS OF ROUGH SEAS. CHANCE OF
RAIN SHOWERS, ISOLATED THUNDERSTORMS.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...NONE.
SYNOPSIS...FRANK/BW
NEAR TERM...FRANK/NOCERA
SHORT TERM...FRANK
LONG TERM...BW
AVIATION...NOCERA/BW
MARINE...FRANK/BW
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