Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 082254 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 653 PM EDT TUE JUL 8 2014 .SYNOPSIS... VERY WARM TO HOT WEATHER WILL CONTINUE THROUGH WEDNESDAY WITH A FEW THUNDERSTORMS POSSIBLE...BUT DRY WEATHER WILL DOMINATE. MUCH LOWER HUMIDITY AND SEASONABLE WEATHER RETURNS THURSDAY INTO SATURDAY AS HIGH PRESSURE BUILDS IN BEHIND A COLD FRONT. THE HIGH PRESSURE SYSTEM WILL MOVE OFF THE COAST EARLY NEXT WEEK ALLOWING HUMIDITY TO RETURN ALONG WITH THE RISK OF A FEW SHOWERS/THUNDERSTORMS. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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***SEVERE THUNDERSTORM WATCH WESTERN MA/NORTHERN CT THROUGH MIDNIGHT*** ***A LINE OF STRONG TO SEVERE THUNDERSTORMS MAY WORK INTO WESTERN NEW ENGLAND AFTER 10 PM AND WEAKEN AS IT MOVES INTO EASTERN NEW ENGLAND*** 650 PM UPDATE... A LINE OF SEVERE THUNDERSTORMS WAS WORKING ACROSS WESTERN NY AND PENNSYLVANIA EARLY THIS EVENING...WHILE IT REMAINED QUIET ACROSS OUR REGION. THE MAIN UNCERTAINTY IS HOW WELL THIS ACTIVITY WILL HOLD TOGETHER AS IT ENTERS OUR REGION. THE MESOSCALE MODELS HAVE BEEN IN GOOD AGREEMENT THAT THIS LINE WILL WORK INTO OUR WESTERN ZONES AFTER 10 PM. THE MAIN QUESTION IS WILL THE STORMS STILL BE STRONG TO SEVERE WHEN THEY ENTER OUR REGION. WE NORMALLY LIKE TO SEE STEEP MID LEVEL LAPSE RATES IN PLACE FOR A SIGNIFICANT SEVERE WEATHER THREAT INTO THE OVERNIGHT HOURS...WHICH IS MISSING IN THIS CASE. HOWEVER...WERE DEALING WITH 0 TO 6 KM SHEAR VALUES ON THE ORDER OF 40 KNOTS. THIS CAN SOMETIMES LEAD TO A STRONG TO DAMAGING WIND THREAT EVEN WITH CAPES DROPPING BELOW 1000 J/KG. THEREFORE...A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR WESTERN MA AND NORTHERN CT THROUGH MIDNIGHT. THE MAIN THREAT WILL BE STRONG TO DAMAGING STRAIGHT LINE WIND GUSTS IF WE CAN MAINTAIN ENOUGH CAPE IN WESTERN NEW ENGLAND. BRIEF TORRENTIAL RAINFALL WILL ALSO BE POSSIBLE. ACTIVITY MAY EVENTUALLY FIND ITS WAY INTO OUR EASTERN ZONES IN A WEAKENED STATE...BUT CAN/T RULE OUT A FEW THUNDERSTORMS. FINALLY...LOW CLOUDS AND FOG SHOULD DEVELOP TONIGHT ALONG THE SOUTHEAST NEW ENGLAND COAST...WHICH IS SUPPORTED BY ALL THE LATEST GUIDANCE. WILL ALSO HAVE TO WATCH FOR A TOUCH OF ELEVATED CONVECTION DEVELOPING TOWARDS 12Z NEAR CAPE/ISLANDS ON THE NOSE OF THE LOW LEVEL JET.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... WEDNESDAY AND WEDNESDAY NIGHT... ANOTHER VERY WARM TO HOT DAY ON TAP FOR THE REGION. ONCE AGAIN HIGHS ARE EXPECTED TO TOP OUT IN THE UPPER 80S AND LOWER 90S. IT WON/T BE QUITE AS HUMID AS THE PAST FEW DAYS AS LOW LEVEL MOISTURE BEGINS TO MIX OUT. LOW CONFIDENCE ON CONVECTIVE POTENTIAL WEDNESDAY AFTERNOON AND EVENING. WILL PROBABLY SEE ABOUT 1000 TO 1500 J/KG OF CAPE...BUT NOT AS MUCH AS THE LAST TWO DAYS WITH LESS LOW LEVEL MOISTURE. 0 TO 6 KM SHEAR IS QUITE IMPRESSIVE FOR JULY STANDARDS ON THE ORDER OF 40 TO 50 KNOTS. HOWEVER...DRY MID LEVEL AIR MAY SIGNIFICANTLY LIMIT UPDRAFT AND CONVECTIVE POTENTIAL. WHILE WE NEVER BASE A FORECAST ON QPF...BELIEVE THIS IS ONE BIG REASON WHY THE MODELS SHOW VERY LITTLE OF IT. WITH ALL THAT SAID...GIVEN VERY HIGH SHEAR AND FRONTAL BOUNDARY SLOWLY WORKING INTO THE REGION THINK WE WILL SEE ISOLATED STORMS BUT WITH LIMITED AREAL COVERAGE. ANY STORM THAT IS ABLE TO DEVELOP COULD BE STRONG TO SEVERE SO STILL NEED TO KEEP A CLOSE EYE ON POTENTIAL. SHOULD SEE DRIER AIR WORK IN BEHIND THE COLD FRONT DURING WEDNESDAY NIGHT...ENDING THE RISK FOR ANY CONVECTION IN MOST AREAS. THE EXCEPTION MAY BE THE SOUTH COAST/CAPE AND ISLANDS...WHERE SCATTERED SHOWERS AND THUNDERSTORMS MAY DEVELOP ON THE NOSE OF THE LOW LEVEL JET AND FRONTAL BOUNDARY PUSHING INTO THE REGION. && .LONG TERM /THURSDAY THROUGH TUESDAY/... HIGHLIGHTS... * FAIR WEATHER THU AND FRI WITH LOWER HUMIDITY. * SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS LATE SAT/EARLY SUN ALONG WITH THE RETURN OF A MORE HUMID AIRMASS. * BETTER CHANCE OF SHOWERS AND THUNDERSTORMS LATE SUN THROUGH TUE WITH LOCALIZED FLASH FLOODING THE MAIN CONCERN AT THIS TIME. * SEASONABLE TEMPERATURES THROUGH THE PERIOD. OVERVIEW AND MODEL PREFERENCES... AT THE MID LEVELS...A RIDGE OVER WESTERN NOAM AND A MORE PERSISTENT RIDGE OVER THE DAVIS STRAIGHT WILL SUPPORT A MEAN TROUGH INVOF HUDSONS BAY THROUGH THE PERIOD. THIS TROUGH WILL EVOLVE INTO AN ANOMALOUS DEEP /-2 TO -3 SD/ CUT-OFF LOW OVER SOUTHERN CANADA IN THE MON-TUE TIMEFRAME. BOTH GFS AND EC OPERATIONAL RUNS AND THEIR RESPECTIVE ENSEMBLES ARE IN FAIRLY GOOD AGREEMENT ON THIS FEATURE... ALTHOUGH THE OPERATIONAL RUNS ARE A BIT MORE AMPLIFIED AND FURTHER SOUTH. THERE IS UNCERTAINTY WITH REGARD TO THE TIMING AND AMPLITUDE OF SHORTWAVE ENERGY ROTATING THROUGH THIS TROUGH...ESPECIALLY LATE SAT INTO EARLY SUNDAY. THE EC/ECENS INDICATES A DEEPER SHORTWAVE MOVING THROUGH THE AREA WHILE THE GFS SHOWS A WEAKER SHORTWAVE... ALTHOUGH SOME OF THE INDIVIDUAL GEFS ENSEMBLE MEMBERS DO SUPPORT THE EC/ECENS SOLUTION. THE NEXT FEATURE IS A COOL FRONT THAT IS PROGGED TO MOVE THROUGH THE REGION ON TUESDAY. DETAILS... THURSDAY...COOL FRONT SHOULD BE IN THE VICINITY OF CAPE COD CANAL AROUND 12Z...BUT MAY BE SLOW TO EXIT...DUE TO FLOW ALOFT BEING INITIALLY PARALLEL TO IT. THIS MAY CAUSE CLOUDS AND SHOWERS TO LINGER ACROSS COASTAL AREAS EARLY IN THE DAY BUT EXPECT A GRADUAL CLEARING TREND AS THE FRONT MAKES SLOW PROGRESS OFFSHORE. THE FLOW REMAINS CYCLONIC ALOFT...BUT WITH A MUCH DRIER AIRMASS FILTERING INTO THE REGION...EXPECT IT TO BE A DRY DAY OTHERWISE. FRIDAY...A WEAK SHORTWAVE MOVES THROUGH EARLY IN THE MORNING BUT THE COLUMN IS DRY SO NOT EXPECTING ANY PRECIP. WEAK RIDGING THEN BUILDS IN ALOFT DURING THE DAY...AND WITH HIGH PRESSURE CENTERED OVER THE REGION AT THE SURFACE...EXPECTING A DRY DAY. SEA-BREEZES LOOK LIKELY ALONG COASTAL AREAS DUE TO A WEAK GRADIENT. SATURDAY AND SUNDAY...HIGH PRESSURE RIDGE MOVES OFFSHORE AND RETURN FLOW WILL LEAD TO A MORE HUMID AIRMASS BEGINNING SATURDAY. LATE SAT AND INTO SUNDAY...A SHORTWAVE IS PROGGED TO MOVE THROUGH...LEADING TO THE CHANCE OF SHOWERS AND THUNDERSTORMS DURING THIS TIMEFRAME. HOWEVER THE TIMING AND AMPLITUDE OF THIS FEATURE IS UNCERTAIN. MONDAY THROUGH TUE... SEVERAL SHORTWAVE DISTURBANCES WILL ROTATE THROUGH AN ANOMALOUSLY DEEP CUT-OFF LOW IN SOUTHERN CANADA WITH SEVERAL ROUNDS OF SHOWERS AND THUNDERSTORMS POSSIBLE. ALTHOUGH SEVERE WEATHER POTENTIAL AT THIS TIMEFRAME IS HIGHLY UNCERTAIN... THIS TYPE OF PATTERN DOES FAVOR FLASH FLOODING...SO THIS POTENTIAL WILL NEED TO BE MONITORED. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH WEDNESDAY NIGHT/... TONIGHT...MODERATE CONFIDENCE. MAINLY VFR CONDITIONS EXPECTED OUTSIDE OF CONVECTION TO THE NORTHWEST OF I-95. HOWEVER...LOW CLOUDS AND FOG WERE IN THE PROCESS OF DEVELOPING ALONG THE SOUTHEAST NEW ENGLAND COAST...SO EXPECT IFR CONDITIONS TO DEVELOP IN THOSE LOCATIONS. AS FOR CONVECTION...A LINE OF STRONG TO POSSIBLY SEVERE THUNDERSTORMS MAY BE ENTERING OUR BDL/BAF TERMINALS AFTER 2Z. IF THEY CAN HOLD TOGETHER...BRIEF TORRENTIAL RAIN AND LOCALLY STRONG WIND GUSTS WILL BE POSSIBLE. WHILE A FEW THUNDERSTORMS MAY SURVIVE THEIR WAY TO THE COASTAL PLAIN...ACTIVITY SHOULD AT LEAST WEAKEN AND BECOME DISORGANIZED. WEDNESDAY AND WEDNESDAY NIGHT...MODERATE CONFIDENCE. LOW CLOUDS AND FOG ALONG SOUTHEAST NEW ENGLAND COAST MAY BURN OFF TEMPORARILY DURING THE LATE MORNING AND AFTERNOON...BUT SHOULD REFORM WED NIGHT. ACROSS THE REST OF THE REGION MAINLY VFR OUTSIDE A FEW SPOT THUNDERSTORMS THIS AFTERNOON AND EVENING. KBOS TAF...HIGH CONFIDENCE IN TAF. LOW PROBABILITY OF A THUNDERSTORM THIS EVENING. KBDL TAF...HIGH CONFIDENCE IN TAF. A LINE OF STRONG THUNDERSTORMS MAY WORK INTO THE REGION AFTER 2Z. OUTLOOK...THURSDAY THROUGH SUNDAY... THURSDAY...MODERATE CONFIDENCE. VFR...EXCEPT MVFR/IFR POSSIBLE IN LOW CLOUDS...SHRA/TSRA EARLY ALONG THE SOUTH AND EAST COASTS. FRIDAY THROUGH SUNDAY...LOW CONFIDENCE. VFR...EXCEPT MVFR/IFR POSSIBLE IN SHRA/TSRA OVER THE FAR NORTHWEST INTERIOR..
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&& .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...MODERATE TO HIGH CONFIDENCE. GUSTY SOUTHWEST WINDS WILL CONTINUE INTO THE EVENING ACROSS SOME OF OUR NEAR SHORE WATERS...SO THESE SCA HEADLINES WILL CONTINUE INTO PART OF THE EVENING. MEANWHILE...ACROSS THE SOUTHERN OPEN WATERS LONG SOUTHWEST FETCH WILL ALLOW PERSISTENT 4 TO 7 FOOT SEAS INTO AT LEAST WEDNESDAY EVENING. IN ADDITION...AREAS OF FOG ARE EXPECTED LATE TONIGHT INTO WED MORNING AND DEVELOP AGAIN WEDNESDAY NIGHT ACROSS THE SOUTHERN WATERS. THERE ALSO IS A LOW RISK OF A STRONG THUNDERSTORM OR TWO WITH GUSTY WINDS ACROSS THE EASTERN WATERS THIS EVENING. OUTLOOK...THURSDAY THROUGH SUNDAY... THURSDAY...MODERATE CONFIDENCE. A COOL FRONT WILL BE MOVING THROUGH THE WATERS EARLY IN THE DAY WITH A CHANCE SHOWERS AND THUNDERSTORMS. SEAS WILL BE AT SCA THRESHOLDS /5-6 FEET/ BUT DECLINING THROUGH THE DAY. FRIDAY THROUGH SUNDAY...HIGH CONFIDENCE. HIGH PRESSURE BUILDS INTO THE REGION...EXCEPT WINDS AND SEAS BELOW SCA THRESHOLDS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT WEDNESDAY FOR ANZ231>234. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ230- 236-251. SMALL CRAFT ADVISORY UNTIL 6 AM EDT THURSDAY FOR ANZ235-237. SMALL CRAFT ADVISORY UNTIL 8 PM EDT WEDNESDAY FOR ANZ250. SMALL CRAFT ADVISORY UNTIL 8 AM EDT THURSDAY FOR ANZ254>256. && $$ SYNOPSIS...FRANK NEAR TERM...FRANK SHORT TERM...FRANK LONG TERM...FRANK/FRANCK AVIATION...FRANK/FRANCK MARINE...FRANK/FRANCK

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