Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 291347 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 947 AM EDT FRI AUG 29 2014 .SYNOPSIS... HIGH PRESSURE CENTERED OVER THE GREAT LAKES WILL BUILD OVER NEW ENGLAND WITH DRY WEATHER AND LOW HUMIDITY TODAY AND SATURDAY. ROUGH SURF AND RIP CURRENTS WILL DIMINISH BY TONIGHT. A FRONT WILL SLOWLY PUSH ACROSS NEW ENGLAND LATE SUNDAY AND MONDAY BRINGING A PERIOD OF SHOWERS AND SCATTERED THUNDERSTORMS. SOME SHOWERS AND A FEW THUNDERSTORMS MAY LINGER INTO TUESDAY. WARM...DRY CONDITIONS LOOK TO SET UP BY LATE NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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10 AM UPDATE... NO MAJOR CHANGES TO PREVIOUS FORECAST. 12Z OBSERVED SOUNDINGS AT CHATHAM AND UPSTREAM AT ALBANY NY REVEAL STRONG MID LEVEL SUBSIDENCE INVERSION...COURTSEY OF 1023 MB HIGH OVER SOUTHERN QUEBEC. GIVEN THE CANADIAN ORIGINS OF THIS AIRMASS IT WILL BE COOLER THAN NORMAL TODAY WITH HIGHS MAINLY IN THE 70S. HOWEVER PLENTY OF LATE AUG SUNSHINE WILL PROVIDE PLEASANT CONDITIONS. EARLIER DISCUSSION BELOW. ================================================================= PREVIOUS DISCUSSION... HIGH PRESSURE BUILDS OVER NEW ENGLAND AT THE SURFACE AND ALOFT WHILE YESTERDAY/S UPPER TROUGH MOVES OFF THROUGH THE MARITIMES. WHILE THERE WILL BE SOME LINGERING PRESSURE GRADIENT THIS MORNING...THIS SHOULD BECOME LIGHT AS THE HIGH MOVES OVERHEAD. THE LIGHT GRADIENT WILL ALLOW FOR SEA BREEZES DEVELOPING LATER THIS MORNING AND THIS AFTERNOON ALONG ALL COASTLINES. CROSS SECTIONS OF RELATIVE HUMIDITY SHOW A LAYER OF HIGH MOISTURE ALSO LINGERING BETWEEN 800 AND 850 MB. MIXING WILL REACH TO AT LEAST THE BASE OF THAT LAYER. EXPECT ANOTHER ROUND OF DIURNAL CUMULUS...BUT WITH INCREASING SUBSIDENCE THE SKY COVER SHOULD BE LESS THAN YESTERDAY. TEMPS AT 850 MB WILL BE 8-10C WHICH SUPPORTS MAX SFC TEMPS IN THE 70S...POSSIBLY NEAR 80 IN A FEW WARM SPOTS SUCH AS THE LOWER CT VALLEY. SEA BREEZES WILL BUFFER COASTAL TEMPS...WATER TEMPS ARE IN THE 60S EAST OF MASS AND AROUND 70 ALONG THE SOUTH COAST. SO COASTAL TEMPS SHOULD BE IN THE 60S AND LOWER 70S. A 5 FOOT SOUTH SWELL LINGERS ON THE SOUTHERN WATERS THIS MORNING...BUT SHOULD BE TRENDING LOWER THROUGH THE DAY. WE WILL CONTINUE THE HIGH SURF ADVISORY THROUGH THE MORNING BUT BRING THE ENDING TIME FORWARD TO 2 PM.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... HIGH PRESSURE MOVES OFFSHORE TONIGHT AND REMAINS IN PLACE TO OUR EAST ON SATURDAY. THIS WILL BRING INCREASING FLOW FROM THE SOUTH...EXCEPT SOUTHEAST NEAR THE EAST MASS COAST. DEW POINTS WILL START TO RISE...BUT THIS TREND MAY HOLD OFF UNTIL THE FLOW PICKS UP ON SATURDAY. AT THAT POINT...DEW POINT VALUES WILL CLIMB THROUGH THE 50S TO NEAR 60 BY SATURDAY EVENING. TONIGHT... THE LIGHT WIND/FAIR SKIES WILL ALLOW ANOTHER COOL NIGHT TONIGHT WITH SURFACE TEMPS IN THE UPPER 40S AND 50S. THIS WILL BE CLOSE ENOUGH TO SATURATION FOR PATCHY FOG. BEST CHANCES WOULD BE IN THE CT VALLEY AND IN THE LOW SPOTS OF EASTERN MASS. SATURDAY... SUNSHINE THROUGH CIRRUS ON SATURDAY WILL MEAN A PLEASANT DAY. THE SUNSHINE WILL BE FILTERED A LITTLE...BUT TEMPS IN THE MIXED LAYER WILL BE A LITTLE MILDER THAN TODAY. SO SFC TEMPS SHOULD BE AT LEAST THE SAME AS TODAY AND PROBABLY A LITTLE MILDER. BASED ON A MIXED LAYER TO 900 MB OR A LITTLE ABOVE...WE WENT WITH MAX TEMPS 75 TO 80. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... OVERVIEW AND MODEL PREFERENCES... NOTING OVERALL CHANGES ON THE MEDIUM RANGE MODELS TOWARD A BROAD RIDGING PATTERN DEVELOPING ACROSS THE EASTERN SEABOARD...MORE OF A TYPICAL SUMMER PATTERN THOUGH LATE IN THE SEASON...AS OPPOSED TO THE LONG WAVE TROUGHING THAT HAS BEEN ACROSS THE EAST OVER THE LAST SEVERAL MONTHS. WILL CONTINUE WITH TREND OF BROAD TROUGHING TO START OFF THIS PORTION OF THE FORECAST...THEN TRANSITION TOWARD NEARLY ZONAL NORTHERN TIER UPPER FLOW WHICH THE MODELS/ENSEMBLES HAVE BEEN ADVERTISING OVER THE LAST FEW NIGHTS. MODEL SOLUTION DIFFERENCES IN THE STEERING CURRENTS WORK IN BEGINNING EARLY NEXT WEEK...SO SOME QUESTION AS TO TIMING OF SURFACE SYSTEMS TO THE EASTERN SEABOARD. LEANED TOWARD A BLEND OF AVAILABLE GUIDANCE THROUGH LATE MONDAY... WHICH SHOWED GOOD RUN TO RUN CONSISTENCY OVER THE LAST SEVERAL DAYS. FOR TUESDAY AND BEYOND...WENT CLOSER A BLEND OF THE EC/GEFS ENSEMBLE MEANS. WITH SOLUTION TIMING ISSUES...HAVE LOWER CONFIDENCE DURING THIS TIMEFRAME. DETAILS... SATURDAY NIGHT THROUGH SUNDAY NIGHT... LARGE SURFACE HIGH SLOWLY PUSHES E OF NEW ENGLAND DURING THIS TIMEFRAME. LOOKS LIKE THIS WILL BE SLOW TO CLEAR THE COAST...SO HAVE CARRIED DRY CONDITIONS. PERSISTENT SW WINDS WILL BRING IN MORE HUMIDITY TOWARD THE REGION ESPECIALLY ON SUNDAY AHEAD OF AN APPROACHING FRONT. DEWPTS FORECASTED TO INCREASE TO THE MID 60S TO AROUND 70 DEGS DURING SUNDAY. WILL SEE PATCHY FOG DEVELOP SAT NIGHT MAINLY AFTER MIDNIGHT WITH LOWS IN THE LOWER-MID 60S. A FRONTAL SYSTEM WILL SHIFT SLOWLY E DURING SUNDAY...SO WILL SEE CLOUDS INCREASING AS WELL AS THE HUMIDITY. WILL START TO SEE SHOWERS AND SOME SCT THUNDERSTORMS PUSH INTO WESTERN AREAS DURING THE AFTERNOON...WITH THE BEST SHOT FOR PRECIP DURING SUN NIGHT. MODELS SIGNALING A SHARP INCREASE IN PWATS AS WELL...ON THE ORDER OF 2.1 TO 2.3 INCHES...WHICH RUNS CLOSE TO 3 SD ABOVE NORMAL FOR EARLY SEPTEMBER BY SUN NIGHT. SO...WILL PROBABLY SEE SOME HEAVY DOWNPOURS WITH SOME OF THESE SHOWERS AND STORMS. PRETTY GOOD INSTABILITY ALSO MOVING ACROSS WITH K INDICES IN THE LOWER-MID 30S...ALONG WITH A BAND OF BELOW ZERO SHOWALTER INDICES CROSSING THE REGION SUN NIGHT. HIGHS ON SUNDAY WILL BE STEAMY...IN THE LOWER-MID 80S...WITH LOWS SUN NIGHT BETWEEN 65 AND 70 DEGREES. MONDAY... FRONT CROSSES THE REGION AS IT WASHES OUT...BUT MOISTURE LINGERS ACROSS THE REGION ALONG WITH THE HIGH HUMIDITIES. KEPT CHANCE POPS GOING DURING THE DAY INTO EVENING HOURS MAINLY DUE TO DIURNAL HEATING. ALSO HAVE MENTIONED CHANCE FOR THUNDER ACROSS CENTRAL AND SOUTHERN AREAS. EXPECT PRECIP TO WEAKEN MON NIGHT. WILL REMAIN WARM AND HUMID. TUESDAY... ANOTHER COLD FRONT APPROACHES...SO WILL SEE ANOTHER ROUND OF SCT SHOWERS/TSTMS. WARM AND HUMID CONDITIONS WILL CONTINUE WITH HIGHS AGAIN IN THE LOWER-MID 80S. THE FRONT SHOULD CLEAR THE COAST TUE NIGHT...BUT WIND FLOW REMAINS FROM THE W WITH THE DRIER AIR REMAINING N OF THE REGION. WEDNESDAY AND THURSDAY... SOMEWHAT DRIER AIR WILL WORK INTO THE REGION DURING THIS TIMEFRAME...BUT TEMPS LOOK TO REMAIN ON THE WARM SIDE AS A RIDGE BUILDS ACROSS THE EASTERN U.S. STILL SOME QUESTIONS WITH THE EVOLVING UPPER LEVEL PATTERN ACROSS THE CONUS...SO LOWER CONFIDENCE ON THIS PORTION OF THE FORECAST. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 10 AM UPDATE... NO MAJOR CHANGES TO 12Z TAFS. SHORT TERM /TODAY THROUGH SATURDAY/...HIGH CONFIDENCE. VFR. PATCHY IFR FOG LATER TONIGHT/EARLY SATURDAY IN THE CT VALLEY AND IN THE LOW SPOTS OF E MASS. AS NE WINDS DIMINISH THIS MORNING...WINDS BECOME ONSHORE ALONG IMMEDIATE E COAST DURING THE AFTERNOON. ON SAT...SEA BREEZES WILL DEVELOP ON ALL COASTS. THIS WILL DIMINISH TOWARD EVENING. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. SEA BREEZES DEVELOP INITIALLY TURNING NORTHEAST LATE MORNING...THEN SOUTHEAST BY MID AFTERNOON AND SOUTH AT SUNSET. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...SATURDAY NIGHT THROUGH TUESDAY... SATURDAY NIGHT AND SUNDAY...MODERATE CONFIDENCE. MAINLY VFR. S/SW WINDS GUSTING UP TO 20-25 KT DURING SUNDAY. MVFR- IFR CIGS/VSBYS POSSIBLE ALONG THE S COAST SATURDAY NIGHT. CHANCE FOR SHRA/TSRA ACROSS CENTRAL AND WESTERN AREAS BEGINNING AROUND MIDDAY SUNDAY ONWARD. SUNDAY NIGHT AND MONDAY...LOW CONFIDENCE. MIX OF LOW END VFR TO MVFR. WIDESPREAD SHRA ACROSS THE TERMINALS. POSSIBLE TSRA ACROSS THE INTERIOR MONDAY. CONTINUED S/SW WINDS. TUESDAY...MODERATE CONFIDENCE. COLD FRONT SWEEPING ACROSS THE TERMINALS LATE TUE/TUE NIGHT. LOW END VFR. CHANCE OF SHRA/TSRA. WINDS BACKING OUT OF W BEHIND THE FRONT TUE NIGHT.
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&& .MARINE...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. 10 AM UPDATE... SE SWELLS CONTINUE TO SLOWLY DIMINISH ALONG WITH N-NE WINDS AS HIGH PRES CREST OVER CAPE COD LATER TODAY. EARLIER DISCUSSION BELOW. SHORT-TERM /TONIGHT THROUGH FRIDAY NIGHT/...HIGH CONFIDENCE. TODAY...HIGH PRESSURE BUILDS OVER THE WATERS. THIS MEANS NORTH WINDS WILL DIMINISH AND BECOME LIGHT. LIGHT WINDS WILL ALLOW SEA BREEZES TO DEVELOP NEAR SHORE. A 5 FOOT SOUTH SWELL FROM CRISTOBAL LINGERS ON THE EXPOSED WATERS BUT IS SHOWING A LOWERING TREND. WE WILL CONTINUE THE SMALL CRAFT ADVISORY FOR A FEW MORE HOURS...ENDING IT ON THE SOUNDS BY 8 AM...AND ON ALL OUTER WATERS BY 2 PM. TONIGHT...SEAS WILL BE BELOW 5 FEET AND WINDS LIGHT. SATURDAY...WINDS INCREASE FROM THE SOUTH...BUT SEA WILL REMAIN BELOW 5 FEET. SATURDAY NIGHT AND SUNDAY...MODERATE CONFIDENCE. S-SW WINDS GUSTING UP TO 20 KT MAINLY ON THE SOUTHERN OUTER WATERS ALONG WITH SEAS BUILDING UP TO AROUND 5 FT. PATCHY FOG WITH REDUCED VSBYS. SCT SHOWERS/TSTMS POSSIBLE ON THE NEAR SHORE WATERS LATE SUN. SUNDAY NIGHT AND MONDAY...MODERATE CONFIDENCE. S-SW WINDS GUSTING UP TO 20 KT WITH SEAS AROUND 5 FT MAINLY ON THE SOUTHERN OUTER WATERS. MAY SEE PATCHY FOG DEVELOP LATE SUN NIGHT INTO MON MORNING. TUESDAY...MODERATE CONFIDENCE. EXPECT SW WINDS BELOW SMALL CRAFT CRITERIA ALONG WITH SEAS BELOW 5 FT.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...HIGH SURF ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR MAZ022- 024. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 AM EDT THIS MORNING FOR ANZ250. SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 2 PM EDT THIS AFTERNOON FOR ANZ254>256.
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&& $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB/NOCERA/EVT SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/NOCERA/EVT MARINE...WTB/NOCERA/EVT

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