195
FXUS61 KBOX 060624
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
224 AM EDT MON JUL 6 2020
SYNOPSIS
A WEAK COLD FRONT AND UPPER-LEVEL TROUGH WILL DEVELOP ISOLATED
SHOWERS AND THUNDERSTORMS THIS EVENING ACROSS NORTHEAST
MASSACHUSETTS. WEAK HIGH PRESSURE FOLLOWS MONDAY AND MOVES OFF
THE COAST TUESDAY. HOT AND HUMID CONDITIONS MOVE IN FOR THE
MIDDLE AND END OF NEXT WEEK WITH SCATTERED AFTERNOON/EVENING
THUNDERSTORMS WEDNESDAY THROUGH FRIDAY. HEAT ADVISORIES MAY BE
NEEDED. LOW PRESSURE PASSING TO OUR SOUTH SATURDAY COULD BRING
MORE WIDESPREAD SHOWERS AND THUNDERSTORMS TO THE REGION. WITH
ABUNDANT MOISTURE IN PLACE LATE IN THE WEEK, ANY STORMS COULD
PRODUCE LOCALLY TORRENTIAL RAINFALL.
NEAR TERM /UNTIL 6 AM THIS MORNING/
215 AM UPDATE:
ACTIVE LATE-EVENING TO AFTER-MIDNIGHT PERIOD WITH A HANDFUL OF
SEVERE STORMS AND A COUPLE SUPERCELLS WHICH AFFECTED SECTIONS OF
OF EASTERN AND NORTHEASTERN MA. WHILE THE SEVERE THREAT HAS
ENDED, STILL HAVE A FEW STRONG THUNDERSTORMS ASSOCIATED WITH
WEAK LOW PRES AND RELATED COLD FRONT ACROSS CAPE COD, NANTUCKET
SOUND AND THE EASTERN WATERS OFF CAPE COD. RADAR TRENDS ARE
GENERALLY ON THE DOWNSWING, THOUGH GOES GLM FLASH-EXTENT
DENSITIES AND CONVENTIONAL ENTLN LIGHTNING TRENDS CONTINUE TO
INDICATE ACTIVE AND FREQUENT IN-CLOUD AND OCCASIONAL CG
LIGHTNING. REFER TO LATEST SPS/MWS FOR CONVECTIVE THREATS.
FORTUNATELY, THESE STORMS ARE EXPECTED TO CLEAR INTO THE OUTER
WATERS WITHIN THE NEXT HOUR TO 90 MINUTES. RE-SHAPED POPS TO
BETTER REFLECT THESE TRENDS.
THEREAFTER, IT APPEARS PROBABLE THAT POST-FRONTAL NORTHERLY
FLOW WILL HELP TO DRAG AN AREA OF STRATUS FROM COASTAL ME/NH
SOUTHWARD INTO EASTERN MA, WHILE MUCH OF THE INTERIOR REMAINS
GENERALLY CLEAR. THOUGH CONVECTION BROUGHT A BRIEF LIFT TO LOW
CEILINGS ACROSS THE CAPE AND SOUTH COAST, THESE WILL ALSO FILL
BACK IN/LOWER.
NO CHANGES TO TEMPS WHICH STILL APPEAR ON TRACK.
SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/
MONDAY...
SURFACE WAVE NEAR CAPE COD EARLY EXITS OUT TO SEA WITH WEAK HIGH
PRESSURE BUILDING INTO THE MARITIMES. THIS YIELDS A LIGHT N-NE FLOW
INTO THE REGION, PROVIDING COOLER TEMPS FOR EASTERN MA WITH HIGHS
ONLY IN THE 70S FOR THE IMMEDIATE COASTLINE INCLUDING BOSTON. THIS
NORTHEAST FLOW IS VERY SHALLOW WITH 925 MB TEMPS WARMING TO +22C
OVER WESTERN CT. THIS WILL SUPPORT HIGHS IN THE 80S ACROSS RI INTO
CENTRAL MA AND TOPPING OUT AROUND 90 IN THE CT RIVER VALLEY
INCLUDING HARTFORD. NOT QUITE AS HUMID AS TODAY WITH DEW PTS IN THE
LOW TO MID 60S EXCEPT UPPER 50S IN WESTERN MA. DRY WEATHER FOR MOST
OF THE REGION, THE ONLY EXCEPTION IS OVER WESTERN CT/MA WHERE AN
ISOLATED SHOWER/T-STORM POSSIBLE GIVEN CLOSER TO DEEPER
MOISTURE/INSTABILITY AND LOW LEVEL CONVERGENCE FROM WARM FRONT
ACROSS EASTERN NY.
MONDAY NIGHT...
MAINLY DRY AND LESS HUMID AS 1023 MB MARITIME HIGH BUILDS SOUTHWARD
INTO GULF OF ME AND CAPE COD.
LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/
HIGHLIGHTS
* HEAT AND HUMIDITY RETURNS FOR THE MIDDLE AND SECOND HALF OF THE
WEEK - COULD REACH 'HEAT ADVISORY' STATUS.
* TROPICAL MOISTURE TO INFLUENCE SOUTHERN NEW ENGLAND LATE WEEK INTO
NEXT WEEKEND.
TUESDAY
A QUASI-STATIONARY FRONT WILL SLOWLY DRIFT FROM SOUTH TO NORTH
ACROSS SOUTHERN NEW ENGLAND. THIS WILL GIVE US THE CHANCE FOR
THUNDERSTORMS DURING THE AFTERNOON HOURS. CAPE VALUES, ESPECIALLY
ACROSS WESTERN MA/CT, ARE FORECASTED TO BE BETWEEN 500 AND 1200
J/KG. ADDITIONALLY, IT DOESN'T APPEAR TO BE A WASHOUT OF A DAY, BUT
AN ISOLATED HEAVY DOWNPOUR OR TWO ARE POSSIBLE AS PWAT VALUES ARE
BETWEEN 1.50" AND 2.00".
WEDNESDAY THOUGH THURSDAY
WE BEGIN TO CRANK UP THE HEAT FOR THE MID-WEEK. TEMPERATURES AT
850MB REACH +15C TO +17C. MIXING TO THOSE HEIGHTS, TEMPERATURES AT
THE SURFACE SHOULD REACH WELL INTO THE UPPER 80S TO LOW 90S ACROSS
MA/RI/CT. DEWPOINTS WILL ALSO BECOME UNCOMFORTABLE - REACHING THE
LOW 70S. THIS WILL GIVE US A HEAT INDEX (APPARENT TEMPERATURE) IN
THE MIDDLE AND UPPER 90S, WHICH MAY REQUIRE A 'HEAT ADVISORY'.
SIMILAR TO LAST WEEK, DIURNAL HEATING AND SUFFICIENT SBCAPE BETWEEN
1000 AND 1500 J/KG WILL ALLOW FOR POP-UP THUNDERSTORMS.
FRIDAY THROUGH NEXT WEEKEND
AS OF 2 PM SATURDAY THE NATIONAL HURRICANE CENTER GAVE AN AREA OF
STORMS OFF THE COAST OF LOUISIANA A 40 PERCENT CHANCE OF TROPICAL
FORMATION OVER THE NEXT FIVE DAYS. SO FAR, THE GUIDANCE SUGGESTS IT
WILL MOVE ACROSS NORTHERN FLORIDA AND UP THE EAST COAST. THE EURO
BRINGS THIS AREA OF LOW PRESSURE UP TOWARDS SOUTHERN NEW ENGLAND
EARLIER SATURDAY, WHILE THE GFS IS MORE PROGRESSIVE, HAVING THE
ARRIVAL ON FRIDAY. WHAT MODELS DO AGREE ON IS THAT THERE WILL BE
ANOMALOUSLY HIGH PWAT VALUES - AROUND 2.00" TO 2.50". THAT IS
BETWEEN 2 TO 3 STANDARD DEVIATIONS ABOVE AVERAGE. WITH THE
POSSIBILITY OF HEAVY RAIN FOR AN EXTENDED PERIOD OF TIME, THE THREAT
FOR FLOODING WILL BE MONITORED. BESIDES THE THREAT FOR HEAVY
RAINFALL - SWELLS WILL INCREASE OFF SHORE FOR FRIDAY INTO MUCH OF
NEXT WEEKEND. CONFIDENCE REMAINS MODERATE FOR THIS PERIOD OF THE
FORECAST.
AVIATION /06Z MONDAY THROUGH FRIDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
06Z TAF UPDATE:
OVERNIGHT THRU 12Z: HIGH CONFIDENCE IN TRENDS, MODERATE ON
TIMING.
LOCAL TSRA/+TSRA FOR CAPE COD TERMINALS AND ADJACENT WATERS TO
BUILD EAST THRU 07-0730Z WITH FREQUENT LIGHTNING, MVFR-IFR
VISBY RAIN AND OCCASIONAL BRIEF WIND GUSTS.
OTHERWISE, FOR THE REST OF THIS PERIOD...ALONG/WEST OF PVD/ORH,
VFR TO PREVAIL. EXPECTING DEGRADED FLIGHT CATEGORIES /SUB-VFR
ELSEWHERE. IFR- LIFR STRATUS EITHER RE-ASSERTS ITSELF (FOR THE
CAPE/ACK TERMINALS) OR BUILDS SOUTHWARD FROM ME/NH IN PREVAILING
NORTHERLY FLOW (FOR BVY-BOS-BED-OWD). 4-6 SM BR POSSIBLE IN
MIST. IFR-LIFR BR/FG ON THE CAPE. CONFIDENCE ON TIMING IFR-LIFR
BUILDING SOUTH FROM NH/ME IS NO BETTER THAN MODERATE, BUT
THINKING SOONER THAN LATER.
TODAY: HIGH CONFIDENCE IN TRENDS, MODERATE ON TIMING AND ON
DEVELOPMENT/EXTENT OF TSRA IN FAR SOUTHWEST.
RESTRICTED CONDITIONS EASTERN AIRPORTS TO IMPROVE BY MID-
MORNING, EXCEPT LATE-AM/EARLY-PM ACROSS THE CAPE AIRPORTS AND
ACK. SHOULD SEE ENSUING VFR FOR ALL AFTER 18Z, THOUGH POTENTIAL
FOR TSRA NEAR VICINITY OF WARM FRONT AFTER 20Z. BEST CHANCE
FROM A HFD-IJD LINE SOUTH/WEST, BUT NORTHWARD EXTENT COULD BE
AS FAR AS BAF-CEF. NOT OF THE REALM OF POSSIBILITY THAT TSRA
HERE COULD BE STRONG, BUT BETTER CHANCES FOR STRONGER TSRA
FURTHER SOUTHWEST. N TO NE WINDS 4-8 KT WILL VEER TO E LATE,
WITH ESE WINDS ACROSS CT NEAR VICINITY OF WARM FRONT.
TONIGHT: MODERATE CONFIDENCE.
POSSIBLE SUB-VFR VISBY SHOWERS/T-STORM BUILDING NORTH EARLY IN
THE PERIOD FROM ORH WEST. FLOW TO TURN SE ON PERIPHERY OF WARM
FRONT AND HIGH PRESSURE OVER THE MARITIMES, WHICH SHOULD ALLOW
FOR RETURNING MVFR-LIFR STRATUS LAYER TO ADVANCE BACK NW FOR
MOST. LOW TO MODERATE CONFIDENCE ON TIMING, BUT THINKING AFTER
06Z.
TUESDAY: MODERATE CONFIDENCE.
DRY CONDITIONS, THOUGH CONTINUED MOIST SE FLOW/WINDS SHOULD
MAINTAIN SUB- VFR CONDITIONS. WHILE SOME GUIDANCE ALLOWS BRIEF
VFR INTERVALS, TRENDED CEILINGS MORE PESSIMISTICALLY. COULD SEE
SHRA/POSSIBLE TSRA FROM BDL- WST SOUTHWEST BUT LOW- PROB.
KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. BRF VFR TO TREND
IFR/MVFR OVERNIGHT. THINKING SCATTERING OUT TO VFR AFTER AM
PUSH.
KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. POSSIBLE VCTS/TSRA
AFTER 20Z, THOUGH BETTER CHANCE HFD-IJD SOUTH.
OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/...
TUESDAY: MAINLY MVFR, WITH AREAS VFR POSSIBLE. BREEZY. CHANCE
SHRA, CHANCE TSRA.
TUESDAY NIGHT: MAINLY IFR, WITH LOCAL MVFR POSSIBLE. BREEZY.
CHANCE SHRA, CHANCE TSRA, PATCHY BR.
WEDNESDAY: MVFR/IFR CONDITIONS POSSIBLE. BREEZY. CHANCE SHRA,
CHANCE TSRA.
WEDNESDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. BREEZY.
SLIGHT CHANCE SHRA, SLIGHT CHANCE TSRA, PATCHY BR.
THURSDAY: MAINLY VFR, WITH AREAS MVFR POSSIBLE. BREEZY. CHANCE
SHRA, CHANCE TSRA.
THURSDAY NIGHT: MAINLY VFR, WITH AREAS MVFR POSSIBLE. CHANCE
SHRA.
FRIDAY: MAINLY MVFR, WITH LOCAL VFR POSSIBLE. BREEZY. CHANCE
SHRA, CHANCE TSRA.
MARINE
755 PM UPDATE...
TONIGHT... WEAK LOW PRESSURE FORMS ON A FRONT OVER SOUTHERN NEW
ENGLAND. LIGHT S-SE WINDS AHEAD OF THE FRONT ALONG WITH LOW CLOUDS
AND PATCHY FOG. CHANCE OF A T-STORM OVER NORTHEAST MA WATERS.
MONDAY...WEAK LOW EXITS INTO GEORGES BANK WITH LIGHT N-NE WINDS OVER
MA/RI WATERS. DRY WEATHER AND ANY VSBY RESTRICTIONS IN THE MORNING
IMPROVE IN THE AFTERNOON.
MONDAY NIGHT...1023 MB HIGH OVER THE MARITIMES PROVIDES DRY/TRANQUIL
WEATHER.
OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/...
TUESDAY: WINDS LESS THAN 25 KT. CHANCE OF RAIN SHOWERS, CHANCE
OF THUNDERSTORMS, PATCHY FOG. AREAS OF VISIBILITY 1 TO 3 NM.
TUESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT. CHANCE OF RAIN SHOWERS, PATCHY FOG. VISIBILITY 1 TO 3 NM.
WEDNESDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT. CHANCE OF THUNDERSTORMS, SLIGHT CHANCE OF RAIN SHOWERS,
PATCHY FOG. VISIBILITY 1 TO 3 NM.
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. LOCAL VISIBILITY 1 TO
3 NM.
THURSDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
THURSDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS
APPROACHING 5 FT. CHANCE OF RAIN SHOWERS.
FRIDAY: WINDS LESS THAN 25 KT. AREAS OF ROUGH SEAS. CHANCE OF
RAIN SHOWERS, CHANCE OF THUNDERSTORMS.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...NONE.
SYNOPSIS...NOCERA/GAUCHER/GAF
NEAR TERM...NOCERA/LOCONTO
SHORT TERM...NOCERA
LONG TERM...GAUCHER/GAF
AVIATION...LOCONTO
MARINE...NOCERA/LOCONTO/GAUCHER/GAF
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