819
FXUS61 KBOX 012319
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
719 PM EDT WED JUL 1 2026
WHAT HAS CHANGED
NO SIGNIFICANT CHANGES TO THE FORECAST.
KEY MESSAGES
- DANGEROUS PROLONGED HEAT AND HUMIDITY CONTINUES THROUGH SAT
WITH MAX AFTERNOON HEAT INDICES IN THE 100 TO 115 DEGREE RANGE
WITH LITTLE RELIEF AT NIGHT. PEAK OF THE HEAT REMAINS THU INTO
FRI.
- WEST/NORTHWEST FLOW ALOFT MAY BRING A LOW CONVECTIVE/SEVERE
WEATHER RISK THROUGH FRI. HOWEVER, THE LACK OF A TRIGGER AND
SOME CAPPING MAY KEEP US MAINLY DRY. GREATEST RISK FOR
THUNDERSTORMS/SEVERE WEATHER POTENTIAL MIGHT WAIT UNTIL
INDEPENDENCE DAY WITH THE ACTUAL COLD FRONT.
DISCUSSION
KEY MESSAGE 1...DANGEROUS PROLONGED HEAT AND HUMIDITY CONTINUES
THROUGH SAT WITH MAX AFTERNOON HEAT INDICES IN THE 100 TO 115
DEGREE RANGE WITH LITTLE RELIEF AT NIGHT. PEAK OF THE HEAT
REMAINS THU INTO FRI.
RIDGING OVER THE MID SOUTH WILL SLOWLY MOVE EASTWARD TOWARDS THE
CAROLINAS AND VA THURSDAY AND FRIDAY. HEIGHTS RISE ACROSS THE AREA,
WITH 500MB HEIGHTS IN THE 590-592 DAM RANGE BY THURSDAY. THIS RANKS
WELL ABOVE THE 90TH PERCENTILE AMONG THE KBOS RAOBS, PER THE SPC
SOUNDING CLIMATOLOGY PAGE. EFI DATA ALSO CONTINUES TO SHOW PLENTY OF
EVIDENCE FOR AN ANOMALOUS HEAT WAVE.
HEAT INDICES CONTINUE TO HOVER BETWEEN 99-110 AWAY FROM THE SOUTH
COAST. THE HEAT AND HUMIDITY COMBINATION WILL BE AT ITS WORST IN THE
CT AND MERRIMACK RIVER VALLEYS, WHERE HEAT INDICES MAY GET UP TO 110-
114F IN SOME SPOTS THURSDAY. THE TEMPERATURES THEMSELVES WILL TOP
OUT AT 100-103F. EXTREME HEAT WARNING IN EFFECT THROUGH 8 PM EDT
SATURDAY FOR ALL OF SOUTHERN NEW ENGLAND EXCEPT THE CAPE AND
ISLANDS.
ALONG THE CAPE AND ISLANDS, COOLER WATERS WILL HELP KEEP THE LAND
SLIGHTLY COOLER, BUT THAT DOESN'T STOP THE HEAT/HUMIDITY
COMBINATION. HIGHS THURSDAY IN THE MID-TO-UPPER 80S, BUT THE HEAT
INDEX WILL SHOOT UP TOWARDS 95-98F. HEAT ADVISORY IN EFFECT FOR
BARNSTABLE AND DUKES COUNTIES UNTIL 8 PM EDT SATURDAY.
AT LEAST SIMILAR MID LEVEL TEMPS ARE FORECAST FRI, AROUND +22
TO +23C AT 850 MB. THAT PUTS UPPER 90S ON THE TABLE STILL, AND
FOR SOME OF THE TYPICAL WESTERLY WIND HOT SPOTS LIKE THE
MERRIMACK VALLEY TRIPLE DIGITS IS STILL POSSIBLE. WITH GREATER
CONVECTIVE CHANCES THOUGH TEMPS MAY TOP OUT IN THE MID TO UPPER
90S. WITH THE FORECAST DEWPOINTS INTO THE 70S IT WILL STILL FEEL
LIKE WELL OVER 100 DEGREES FOR MOST LOCATIONS. INTO SAT WITH
HEIGHTS FALLING, MID LEVEL TEMPS ALSO TICK DOWN. TEMPS AT 850 MB
STILL SUPPORT MID 90S WITH SOME LINGERING HUMIDITY/HIGH HEAT
INDICES AND HEADLINES LOOK GOOD.
NOT ONLY WILL THIS BE A DANGEROUS PROLONGED PERIOD OF HEAT,
THERE WILL BE LITTLE RELIEF AT NIGHT. LOW TEMPERATURES WILL ONLY
DROP INTO THE MIDDLE 70S IN MOST LOCATIONS AND 75 TO 80 DEGREES
IN THE URBAN CENTERS. IN FACT, BOSTON MAY NOT DROP BELOW 80
DEGREES DURING THE PEAK OF THE HEAT AND HUMIDITY THU NIGHT!
KEY MESSAGE 2...WEST/NORTHWEST FLOW ALOFT MAY BRING A LOW
CONVECTIVE/SEVERE WEATHER RISK THROUGH FRI. HOWEVER, THE LACK OF
A TRIGGER AND SOME CAPPING MAY KEEP US MAINLY DRY. GREATEST
RISK FOR THUNDERSTORMS/SEVERE WEATHER POTENTIAL MIGHT WAIT UNTIL
INDEPENDENCE DAY WITH THE ACTUAL COLD FRONT.
THE OVERALL UPPER PATTERN SUPPORTS CONTINUED WEST TO NORTHWEST
FLOW ALOFT THRU THE END OF THE WEEK. WITHIN THAT FLOW THERE IS
LITTLE SYNOPTIC FORCING FOR ASCENT THAT IS LIKELY TO CONTRIBUTE
TO THUNDERSTORMS DEVELOPMENT. IN ADDITION, MOST AFTERNOONS WILL
FEATURE AT LEAST A SMALL CAP AS THE INFLUENCES OF THE OHIO
VALLEY HIGH PRESSURE CREATES A LITTLE SUBSIDENCE INVERSION
LOCALLY.
FOR CERTAIN WE ARE LOOKING AT ROBUST HEAT AND HUMIDITY THAT
WILL CONTRIBUTE TO HIGH CAPE VALUES FRI AND POSSIBLY EVEN SAT.
GIVEN THE OVERALL LACK OF SYNOPTIC FORCING IF ANY THUNDERSTORMS
DO DEVELOP THEY SHOULD REMAIN ISOLATED. HOWEVER THEY COULD
QUICKLY BECOME SEVERE DUE TO THE INSTABILITY LEVELS. WITH SHEAR
BEING A LIMITING FACTOR, ANY STORMS ARE LIKELY TO COLLAPSE AS
QUICKLY AS THEY INTENSIFY. THE MAIN HAZARD WOULD BE DOWNBURST
WINDS. UPPER LEVEL HEIGHTS BEGIN TO FALL FRI AND THUS WEAKEN THE
CAPPING MORE THAN OTHER DAYS. THIS COULD PROVIDE THE BEST
OPPORTUNITY FOR THUNDERSTORMS TO BE MORE WIDESPREAD IN COVERAGE.
NBM POP INCREASES A LITTLE FRI, ESPECIALLY ALONG THE COAST AND
THRU THE CT RIVER VALLEY, AND EVEN MORE INTO SAT. I WOULD NOT BE
SURPRISED TO SEE THAT NEED TO COME UP A BIT AS CAMS START TO
GET IN RANGE. SHEAR IS FORECAST TO RAMP UP FRI INTO SAT AND AS A
RESULT THIS IS LIKELY THE BEST WINDOW FOR ORGANIZED SEVERE
WEATHER CHANCES. MACHINE LEARNING GUIDANCE IS IN AGREEMENT WITH
FRI/SAT BEING THE MOST LIKELY DAYS TO CENTER THE SEVERE WEATHER
THREAT OVER SOUTHERN NEW ENGLAND. WITH EXTREME HEAT STILL
ONGOING, HAIL WILL BE A LOWER RISK THAN TYPICALLY, AND LARGELY
UNIFORM WIND DIRECTION WILL ALSO LIMIT ANY TORNADO POTENTIAL. SO
STILL EXPECTING THAT DAMAGING WINDS ARE THE PRIMARY HAZARD TO
WATCH.
AVIATION /00Z THURSDAY THROUGH MONDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
00Z TAF UPDATE...
THIS EVENING THROUGH THURSDAY...HIGH CONFIDENCE OUTSIDE OF
DECAYING SHRA/TSRA AT KBOS LATE TONIGHT, IN ADDITION TO FOG
OVER THE CAPE AND ISLANDS THIS EVENING.
VFR CONDITIONS WILL DOMINATE THROUGH THURSDAY. LIGHT SOUTHWEST
WINDS DEVELOP TONIGHT AS SEABREEZES COLLAPSE AND WILL GUST 15 TO
20 KNOTS THU AFTERNOON. TSRA OVER NY AT THIS HOUR ARE FORECAST
TO CONTINUING TOWARDS SOUTHERN NEW ENGLAND WHILE WEAKENING THRU
MIDNIGHT. CURRENT TIME OF ARRIVAL PUTS THEM IN THE VICINITY OF
NORTHEAST MASS AND THEN BOS BETWEEN 05Z AND 07Z. I WILL ADD A
SHORT DURATION PROB30 TO COVER THIS LOW CONFIDENCE OUTCOME. I
ALSO CANNOT RULE OUT SOME AFTERNOON SHRA/TSRA ACROSS ANY PART OF
SOUTHERN NEW ENGLAND THU, BUT CONFIDENCE IN LOCATION AND TIMING
IS LOW.
KBOS TERMINAL...HIGH CONFIDENCE IN TAF OUTSIDE OF THE PROB30 FOR
DECAYING SHRA.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.
OUTLOOK /FRIDAY THROUGH MONDAY/...
FRIDAY: VFR. BREEZY.
FRIDAY NIGHT: VFR.
INDEPENDENCE DAY THROUGH SUNDAY: VFR. SLIGHT CHANCE SHRA,
SLIGHT CHANCE TSRA.
SUNDAY NIGHT: VFR. CHANCE SHRA, SLIGHT CHANCE TSRA.
MONDAY: MAINLY VFR, WITH LOCAL IFR POSSIBLE. CHANCE SHRA,
SLIGHT CHANCE TSRA.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
TODAY THROUGH THURSDAY...HIGH CONFIDENCE.
BERMUDA HIGH PRESSURE WILL RESULT IN A PERSISTENT SW FLOW ACROSS OUR
WATERS. SW WINDS WILL GUST TO 25 KNOTS AT TIMES TODAY THROUGH
THURSDAY AND LONG FETCH WILL RESULT IN SEAS BUILDING TO 3 TO 6 FEET
ACROSS OUR SOUTHERN WATERS. THEREFORE...WE HAVE CONTINUED SMALL
CRAFT HEADLINES FOR OUR SOUTHERN WATERS INTO THURSDAY.
OUTLOOK /FRIDAY THROUGH MONDAY/...
FRIDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING 5 FT.
FRIDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT. SLIGHT CHANCE OF RAIN SHOWERS.
INDEPENDENCE DAY: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN
SHOWERS.
SATURDAY NIGHT: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN
SHOWERS, SLIGHT CHANCE OF THUNDERSTORMS.
SUNDAY: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN SHOWERS.
SUNDAY NIGHT: WINDS LESS THAN 25 KT. CHANCE OF RAIN SHOWERS.
MONDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
CHANCE OF RAIN SHOWERS.
CLIMATE
RECORD HIGH TEMPERATURES:
JULY 1:
KBOS: 98/1872
KBDL: 101/1964
KPVD: 97/1964
KORH: 94/1913
JULY 2:
KBOS: 98/1963
KBDL: 99/1966
KPVD: 98/1941
KORH: 97/1901
JULY 3:
KBOS: 102/1911
KBDL: 102/1966
KPVD: 98/2002
KORH: 96/1911
JULY 4:
KBOS: 104/1911
KBDL: 99/1911
KPVD: 99/1919
KORH: 102/1911
RECORD HIGH MINIMUM TEMPERATURES:
JULY 1:
KBOS: 73/1958
KBDL: 73/1968
KPVD: 71/1968
KORH: 72/2018
JULY 2:
KBOS: 76/2002
KBDL: 73/2018
KPVD: 75/1941
KORH: 73/1963
JULY 3:
KBOS: 80/2002
KBDL: 73/2018
KPVD: 78/2002
KORH: 72/2002
JULY 4:
KBOS: 77/2002
KBDL: 74/2018
KPVD: 77/2002
KORH: 73/2018
JULY 5:
KBOS: 81/1999
KBDL: 77/1999
KPVD: 78/1999
KORH: 73/1999
BOX WATCHES/WARNINGS/ADVISORIES
CT...EXTREME HEAT WARNING UNTIL 8 PM EDT SATURDAY FOR CTZ002>004.
AIR QUALITY ALERT UNTIL 11 PM EDT THIS EVENING FOR CTZ002>004.
MA...EXTREME HEAT WARNING UNTIL 8 PM EDT SATURDAY FOR MAZ002>021-
026.
AIR QUALITY ALERT UNTIL 11 PM EDT THIS EVENING FOR MAZ004>024-
026.
HEAT ADVISORY UNTIL 8 PM EDT SATURDAY FOR MAZ022-023.
RI...EXTREME HEAT WARNING UNTIL 8 PM EDT SATURDAY FOR RIZ001>007.
AIR QUALITY ALERT UNTIL 11 PM EDT THIS EVENING FOR RIZ001>008.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THURSDAY FOR ANZ231>235-
237.
SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ236.
SMALL CRAFT ADVISORY UNTIL 1 AM EDT FRIDAY FOR ANZ254>256.
DISCUSSION...BOATMAN/LEGRO
AVIATION...LEGRO
MARINE...BOATMAN
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