Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 082016 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 416 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/... ***BEST SHOT FOR ORGANIZED SHOWER/THUNDERSTORM ACTIVITY WILL BE AFTER 10 PM IN OUR WESTERN ZONES*** SPC MESO-ANALYSIS SHOWING MLCAPE VALUES NEARING 1500 J/KG ALONG WITH 0 TO 6 KM SHEAR VALUES ON THE ORDER OF 30 TO 40 KNOTS. MOST OF THE SCATTERED SHOWERS/THUNDERSTORMS THAT HAVE DEVELOPED SO FAR HAVE BEEN TO OUR NORTH AND WEST OF OUR REGION....WHERE BETTER FORCING RESIDES. HOWEVER...SOME OF THE MESOSCALE MODELS DO SHOW A FEW THUNDERSTORMS WORKING ACROSS OUR REGION THROUGH EARLY EVENING. GIVEN INSTABILITY/WIND FIELDS CERTAINLY THE RISK FOR A FEW STRONG TO SEVERE THUNDERSTORMS IF THEY ARE ABLE TO FORM IN OUR REGION. WHILE THE ACTIVITY CAN/T BE RULED OUT ANYWHERE...BEST SHOT APPEARS TO BE OUR NORTHWEST ZONES CLOSER TO THE BETTER FORCING. THE MAIN THREATS WITH ANY ACTIVITY WILL BE ISOLATED STRONG TO DAMAGING STRAIGHT LINE WIND GUSTS...BUT ANY DISCRETE CELLS WOULD BE CAPABLE OF PRODUCING HAIL. GIVEN PWATS BETWEEN 1.50 AND 2 INCHES...LOCALLY HEAVY RAINFALL WILL BE THE MAIN CONCERN. ALL IN ALL...ANY STORM THAT DEVELOPS IN OUR REGION THROUGH EARLY EVENING MAY BECOME SEVERE GIVEN THE ENVIRONMENT. HOWEVER...AREAL COVERAGE MAY BE QUITE LIMITED GIVEN THE LACK OF FORCING. THE BIGGER CONCERN FOR MORE WIDESPREAD ACTIVITY WILL BE LATER TONIGHT /AFTER 10 PM/ IN OUR WESTERN ZONES WITH THE CLUSTER OF SHOWERS/THUNDERSTORMS CURRENTLY OVER THE EASTERN GREAT LAKES. MOST OF THE SHORT TERM MODELS MOVE THIS ACTIVITY EAST...BUT IT PROBABLY WON/T GET INTO OUR WESTERN ZONES UNTIL AFTER 02Z. WE NORMALLY LIKE TO SEE STEEP MID LEVEL LAPSE RATES IN PLACE FOR A SIGNIFICANT SEVERE WEATHER THREAT INTO THE OVERNIGHT HOURS. IN THIS CASE THAT IS MISSING...BUT WE DON/T WANT TO COMPLETELY LET OUR GUARD DOWN GIVEN 0 TO 6 KM SHEAR STRENGTHENING TO OVER 40 KNOTS. SO WE CAN/T RULE OUT A FEW STRONG TO SEVERE STORMS ENTERING OUR WESTERN ZONES DURING THE LATE EVENING HOURS...BUT THE HIGHER RISK FOR SEVERE WEATHER WILL BE WEST OF OUR REGION. ACTIVITY MAY EVENTUALLY FIND ITS WAY INTO OUR EASTERN ZONES IN A WEAKENED STATE...IF IT CAN SURVIVE. 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. && .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 NIGHT 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 /20Z TUESDAY THROUGH SUNDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH WEDNESDAY NIGHT/... THIS AFTERNOON INTO TONIGHT...MODERATE CONFIDENCE. TO THE NORTHWEST OF I-95 MAINLY VFR CONDITIONS EXPECTED OUTSIDE OF ANY CONVECTION. TO THE SOUTHEAST OF I-95...IFR CONDITIONS EXPECTED TO DEVELOP IN LOW CLOUDS AND FOG ON SOUTHWEST WINDS TONIGHT. AS FOR CONVECTIVE POTENTIAL...A FEW ISOLATED THUNDERSTORMS ARE POSSIBLE THROUGH EARLY EVENING.. BETTER SHOT AFTER 2Z THIS EVENING WHEN A LINE OF SHOWERS/THUNDERSTORMS MAY APPROACH OUR WESTERN ZONES. LOCALLY STRONG WIND GUSTS AND HEAVY RAIN ARE STILL POSSIBLE. ACTIVITY SHOULD WEAKEN AS IT MOVES EAST. 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.. && .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...FRANCK AVIATION...FRANK/FRANCK MARINE...FRANK/FRANCK

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