Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 021420 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1020 AM EDT WED SEP 2 2015 .SYNOPSIS... VERY WARM WEATHER TODAY WITH TEMPS CLIMBING INTO THE UPPER 80S TO LOW 90S AWAY FROM THE SOUTH COAST. A WEAK COLD FRONT WILL SWEEP ACROSS NEW ENGLAND THURSDAY. CANADIAN HIGH PRESSURE BRINGS A TEMPORARY BREAK FROM THE HEAT AND HUMIDITY FRIDAY FOLLOWED BY A GRADUAL WARMING TREND LABOR DAY WEEKEND. OTHER THAN THE RISK OF SCATTERED THUNDERSTORMS THURSDAY DRY WEATHER PREVAILS. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1030 AM UPDATE... DAYTIME MIXING PROCEEDING ALLOWING FOR FOG TO BURN OFF. FAIRLY WARM AND DRY AIRMASS ALOFT /NEARLY +20C AT H85 PER CHATHAM/. SHOULD WARM UP EASILY INTO THE UPPER-80S TO LOW-90S. MAY NOT REMAIN CONSIDERABLY HUMID. AS WE SAW YESTERDAY...WITH DEEP-LAYER MIXING PROCEEDING...SAW DEWPOINTS DROP INTO THE 50S FOR SEVERAL LOCATIONS. LIKELY TO SEE A REPEAT TODAY. SO NO MUCH ADJUSTMENT WITH THE REAL-FEEL / HEAT INDEX VALUES. SEA-BREEZE CERTAINLY ALONG THE S-COAST...BUT COULD BE A BIT HARD TO COME BY ALONG THE E-COAST WITH SOME DECENT W-FLOW ALOFT. WOULD NOT BE SURPRISED IF WE SEE IT EDGE IN ALONG THE IMMEDIATE E-COAST. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... TONIGHT... ASIDE FROM A FEW BUILDING CI...CONDITIONS ONCE AGAIN REMAIN MOSTLY CLEAR AND WITH WEAK PRES GRADIENT...EXPECT ANOTHER NIGHT WITH RADIATIONAL COOLING POSSIBLE. SFC DWPTS WILL INCREASE THROUGH THE OVERNIGHT HOURS...SO EXPECT A SLIGHTLY HIGHER RISK FOR LATE NIGHT FOG DEVELOPMENT THAN PREVIOUS NIGHTS...PARTICULARLY IN GRASSY VALLEYS AND OTHER FOG PRONE LOCATIONS. MINS MAINLY IN THE LOW-MID 60S. THU... COLD FRONT WILL ALMOST BACKDOOR INTO THE REGION AS EASTERN TROF DEEPENS. NOT A GREAT SETUP FOR SHOWERS/STORMS...HOWEVER WITH PWATS INCREASING TO ABOUT 1 STD DEVIATION ABOVE EARLY SEPTEMBER NORMALS AND WEAK CONVERGENCE ALONG THE PASSING BOUNDARY...EXPECT AT LEAST A RISK SHOWERS ACROSS THE REGION THROUGH PEAK HEATING. T-STORM RISK IS SOMEWHAT IN QUESTION...DECENT MID LVL LAPSE RATES REMAIN IN PLACE AND INCREASED MOISTURE ALLOW FOR WIDER CAPE PROFILES THAN WED. SFC VALUES RANGE FROM ABOUT 1000J/KG TO 2000 FROM THE LESS ROBUST ECMWF TO THE WETTER/MORE UNSTABLE NAM. AS MENTIONED BEFORE...CONVERGENCE IS WEAK...AND SHEAR IS ALMOST NON- EXISTENT WITH BULK SHEAR VALUES STRUGGLING TO EXCEED THE 10-20KT RANGE. THEREFORE...INSTABILITY WILL BE THE ONLY THING TO DRIVE UPDRAFTS. ENOUGH FOR SOME THUNDERSTORMS...BUT ITS LIKELY TO LIMIT SEVERITY...WHICH CORRELATES WELL THE SWODY2 FROM SPC. STILL NOTING SOME 400-600J/KG HAIL CAPES THANKS TO THE WIDE CAPE PROFILES. SOMETHING TO WATCH AS WE APPROACH. HEAT AND HUMIDITY CONTINUES OTHERWISE...WITH HIGHS ONCE AGAIN BETWEEN THE MID 80S AND LOW 90S. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... HIGHLIGHTS... * MILD DAYS/COOL NIGHTS AND LESS HUMID FRI AND SAT * WARMING TREND SUN AND MON * LOW RISK OF SHOWERS/T-STORMS NEXT TUESDAY SYNOPTIC OVERVIEW... BRIEF MID LEVEL TROUGH OVER NEWFOUNDLAND AND LABRADOR RESULTS IN 1027 MB SURFACE HIGH BUILDING SOUTHWARD FROM QUEBEC INTO NEW ENGLAND FRI AND SAT. THIS CANADIAN AIRMASS WILL YIELD MILD DAYS/COOL NIGHTS AND MUCH LOWER HUMIDITY FOR OUR REGION. HOWEVER UPPER AIR PATTERN IS PROGRESSIVE WITH LARGE AMPLITUDE RIDGE AND ASSOCIATED POSITIVE HEIGHT ANOMALY OF +2 STD DEVIATIONS CENTERED OVER ONTARIO FRI BUILDING EAST INTO QUEBEC AND NORTHERN NEW ENGLAND SUN AND MON. THIS WILL RESULT IN A WARMER AIRMASS ADVECTING INTO THE AREA WITH TEMPS CLIMBING BACK TO 85 TO 90 SUN AND MON...LIKELY LINGERING INTO TUE AS WELL. THIS RIDGING WILL KEEP THE NORTHERN STREAM JET AND ASSOCIATED FRONTAL PASSAGES WELL NW OF SOUTHERN NEW ENGLAND. THUS OTHER THAN POTENTIAL SHOWERS/T-STORMS THU DRY WEATHER PREVAILS MUCH OF THIS PERIOD. ENSEMBLES SUGGEST NORTHEAST RIDGE LIKELY BREAKS DOWN EARLY TO MIDDLE OF NEXT WEEK AS UPPER AIR PATTERN DEAMPLIFIES AND BECOMES MORE ZONAL. THIS MAY SUPPORT A FRONTAL PASSAGE AND RISK OF SHOWERS/T- STORMS IN THE TUE/WED TIME FRAME OF NEXT WEEK. DAILY DETAILS... THU NIGHT...LEFTOVER ISOLATED TO SCATTERED SHOWERS/T-STORMS POSSIBLE IN THE EVENING AS COLD FRONT IS SLOW TO DEPART. A FEW HEAVY DOWNPOURS POSSIBLE GIVEN PWATS NEAR 1.75 INCHES /+1 STD DEVIATIONS FROM CLIMO/ MODEST INSTABILITY AND WEAK WINDS ALOFT RESULTING IN SLOW MOVING STORMS. HOWEVER THE LACK OF DEEP LAYER SHEAR AND MARGINAL MID LEVEL LAPSE RATES SHOULD ALLOW CONVECTION TO WEAKEN RAPIDLY AFTER SUNSET. NOTICEABLE COOL DOWN 09Z-12Z FRI AS POST FRONTAL AIRMASS INVADES THE AREA FROM THE NORTHEAST. FRI...NOTICEABLE AIRMASS CHANGE /COOLER AND LESS HUMID/ AS 1025 MB SURFACE HIGH BUILDS INTO THE REGION. A GUSTY NE WIND WILL ACCOMPANY THE COOLER TEMPS WITH GUSTS UP TO 25 MPH ACROSS CAPE COD AND THE ISLANDS. SOME UNCERTAINTY REGARDING AREAL COVERAGE AND DURATION OF POST FRONTAL STRATO-CU CLOUDS. NAM HAS CLOUDS LINGERING LONGER THAN THE GFS. WILL HEDGE TOWARD A TREND OF INCREASING SUNSHINE AS FRI PROGRESSES WITH COLUMN DRYING FROM NORTH TO SOUTH. FRI NIGHT...MUCH COOLER WITH DRY AIRMASS/LIGHT WINDS AND CLEAR SKIES. SOME OF THE COLDER MOS DATA SETS SUGGEST U40S ARE POSSIBLE IN THE TYPICAL COOLER SPOTS /MVY...I495 CORRIDOR OF EASTERN MA AND INTERIOR VALLEYS OF CT AND MA/. GIVEN SETUP FOR RADIATIONAL COOLING HAVE BLENDED IN THIS COOLER GUIDANCE. SAT...AFTER A COOL START ABUNDANT SUNSHINE RESULTS IN TEMPS REBOUNDING TO NEAR NORMAL WITH HIGHS IN THE U70S AND L80S. COMFORTABLE HUMIDITY CONTINUES WITH DEW PTS REMAINING IN THE 50S. SUNDAY AND MONDAY...MID LEVEL RIDGE CENTERED OVER ONTARIO BUILDS EASTWARD INTO QUEBEC AND NORTHERN NEW ENGLAND. THIS RESULTS IN WARMING TREND WITH TEMPS CLIMBING TO 85-90 AWAY FROM THE COASTLINE. DRY WEATHER CONTINUES. TUESDAY...WARM WEATHER MAY LINGER BUT ENSEMBLES AND DETERMINISTIC GUIDANCE BOTH HINT AT A FRONTAL PASSAGE POSSIBLE AND YIELDING THE RISK OF SHOWERS/T-STORMS. A MODEL BLEND OF POPS OFFERS SLIGHT CHANCE /15%/...WHICH SEEMS REASONABLE AT THIS TIME RANGE. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY/...HIGH CONFIDENCE. 15Z UPDATE... TODAY AND TONIGHT...VFR. IFR-VLIFR FOG WILL ONCE AGAIN BE POSSIBLE AT TYPICALLY PRONE TERMINALS. THURSDAY... VFR. AFTERNOON SHRA/TSRA. TEMPO MVFR IMPACTS. MAIN THREAT +RA. PERHAPS SOME BREEZY WINDS OUT OF THE N AND/OR HAIL SHOULD ANY TSRA BECOME STRONG. THINKING ISOLATED IMPACTS. LOW CONFIDENCE. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. HAVE SE ORIENTED SEA BREEZE BEGINNING LATER...ENDING EARLIER THAN USUAL. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY...HIGH CONFIDENCE. THU NIGHT THROUGH SUNDAY...MAINLY VFR. EXCEPTIONS WILL BE MARGINAL MVFR-VFR CIGS THU NGT INTO FRI MORNING...THEN CLEARING. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY/...HIGH CONFIDENCE. 1030 AM UPDATE...NO MAJOR CHANGES. MAINLY QUIET BOATING WEATHER PREVAILS INTO THU. SEAS BELOW 4 FT AND WINDS GENERALLY AT OR BELOW 20 KT. SOME LATE NIGHT FOG POSSIBLE TONIGHT. THURSDAY...SOME ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE ACROSS THE WATERS WITH LOCALLY ROUGH CONDITIONS. OTHERWISE EXPECT QUIET BOATING WEATHER TO PREVAIL. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY...MODERATE TO HIGH CONFIDENCE. THU NIGHT/FRI...A BURST OF NE WINDS 20 TO 25 KT LATE THU NIGHT INTO FRI MORNING...STRONGEST WINDS EASTERN MA WATERS ALONG WITH LARGEST SEAS. SAT/SUN...LEFTOVER E SWELLS ERODE/DECAY SAT AND GIVE WAY TO LIGHT WINDS AS HIGH PRES BUILDS OVERHEAD. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/DOODY NEAR TERM...NOCERA/DOODY/SIPPRELL SHORT TERM...DOODY LONG TERM...NOCERA AVIATION...NOCERA/DOODY/SIPPRELL MARINE...NOCERA/DOODY

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