Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 170153 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 953 PM EDT SAT AUG 16 2014 .SYNOPSIS... A WARM FRONT WILL BRING A ROUND OF SCATTERED SHOWERS TO THE AREA TONIGHT. ASSOCIATED COLD FRONT SWEEPS ACROSS THE REGION SUNDAY MORNING AND EARLY AFTERNOON WITH ANOTHER ROUND OF SHOWERS AND POSSIBLY A THUNDERSTORM. HIGH PRES ARRIVES MON WITH DRY BUT COOL CONDITIONS. UNSETTLED WEATHER MAY RETURN TUE AND WED OF NEXT WEEK OR MAY STAY SOUTH OF NEW ENGLAND. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... 10 PM UPDATE... PREVIOUS FORECAST MATCHING UP NICELY WITH CURRENT RADAR AND SATELLITE TRENDS. THUS LITTLE IF ANY CHANGE WITH THIS FORECAST UPDATE. STRONG SHORT WAVE TROUGH AND ASSOCIATED JET STREAK APPROACHING WESTERN NY STATE LATE THIS EVENING. THESE STRONG JET DYNAMICS MOVE OVER SOUTHERN NEW ENGLAND 06Z-12Z. HOWEVER AS THE 00Z ALY SOUNDING REVEALS PREFRONTAL ENVIRONMENT IS FAIRLY DRY. THUS SOME OF THE UPSTREAM ACTIVITY WILL WEAKEN/ERODE AS IT INTERACTS WITH THIS DOWNSTREAM DRY AIR. NEVERTHELESS SCATTERED SHOWERS AFTER MIDNIGHT AND ESPECIALLY TOWARD DAYBREAK FROM WEST TO EAST. OTHER AREA TO WATCH IS CONVECTION BEGINNING FIRE WELL SOUTH OF NEW ENGLAND. HIGH THETA-E/MOISTURE AND CAPE ACROSS THIS REGION. AS MID LEVEL TROUGH APPROACHES NEW ENGLAND IT MAY BE ABLE TO CAPTURE/ADVECT THIS AREA OF INSTABILITY/MOISTURE NORTHWARD TOWARD THE CAPE AND ISLANDS. THIS MAY RESULT IN SOME EMBEDDED THUNDER ACROSS THIS AREA TOWARD MORNING. PREVIOUS FORECAST CAPTURES THIS WELL SO AGAIN NOT MANY CHANGES PLANNED WITH THIS FORECAST UPDATE. EARLIER DISCUSSION BELOW. ================================================================= PREVIOUS DISCUSSION... DRY WEATHER CONTINUES THROUGH THIS EVENING. MOISTURE INCREASES ON SOUTHWESTERLY WINDS KEEPING OVERNIGHT TEMPERATURES A BIT WARMER THAN THE PAST FEW NIGHTS. LOW PRESSURE IN ONTARIO THIS AFTERNOON WILL MOVE EASTWARD INTO NORTHERN NEW ENGLAND TONIGHT. A STRONG SHORTWAVE APPROACHING SOUTHERN NEW ENGLAND WILL PROVIDE ENOUGH LIFT FOR SHOWERS TO DEVELOP FROM NORTHWEST TO SOUTHEAST. IN ADDITION...AN AREA OF MID LEVEL LIFT AND MOISTURE COMBINED WITH SOME WEAK INSTABILITY MAY BE ENOUGH FOR A FEW SHOWERS ACROSS THE CAPE AND ISLANDS LATE TONIGHT. A FEW ISOLATED THUNDERSTORMS ARE POSSIBLE ACROSS RHODE ISLAND AND SOUTHEASTERN MASSACHUSETTS WHERE MODEST INSTABILITY EXISTS. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... SHOWERS CONTINUE THROUGH THE MORNING AS THE LOW PRESSURE SYSTEM MOVES INTO NORTHERN NEW ENGLAND AND SHORTWAVE MOVES OFFSHORE. MID LEVEL DRY AIR STARTS MOVING IN BEHIND THE SHORTWAVE AND THIS WILL LIKELY BRING AN END TO MOST OF THE SHOWERS. COLD FRONT STARTS MOVING INTO THE REGION MID-MORNING AND SLOWLY TRANSLATES ACROSS THE AREA... MOVING OFFSHORE BY LATE SUNDAY AFTERNOON. THIS AND THE DRIER AIR WILL START TO CLEAR OUT THE CLOUDS AS WELL...WITH MOSTLY SUNNY SKIES EXPECTED BY THE END OF THE DAY. TEMPERATURES SHOULD BE SIMILAR TO TODAY WITH HIGHS IN THE UPPER 70S TO LOWER 80S. SUNDAY NIGHT...DRIER AIR AND HIGH PRESSURE BUILDING INTO SOUTHERN NEW ENGLAND WILL ALLOW TEMPERATURES TO FALL BACK INTO THE 50S OVERNIGHT. && .LONG TERM /MONDAY THROUGH SATURDAY/... HIGHLIGHTS... *DRIER TO START THE WEEK...BUT INCREASING HUMIDITY TOWARD WEEK/S END *SLOWLY INCREASING TEMPERATURES TOWARD WEEK/S END *DIURNAL SHOWERS TOWARDS THE END OF THE WEEK OVERVIEW... MODELS ARE IN GOOD AGREEMENT TO BEGIN THE PERIOD...BUT DIVERGE TOWARDS THE WEDNESDAY THURSDAY TIMEFRAME AS HAS HAPPENED QUITE OFTEN. THE MAIN OUTLIER IS THE 00Z ECMWF AS IT SHOWS AN UPPER LEVEL LOW STAYING TOGETHER AND MOVING THROUGH THE NORTHEAST. WITH ENSEMBLES LIKE THE NAEFS AND ECENS SHOWING DIFFERENTLY...TRENDED AGAINST THAT FOR THIS PERIOD. THE GENERAL PATTERN SHOWS A STRONG JET ENTERING THE PACIFIC NORTHWEST ALLOWING FOR A RELAXING FROM THE PREVIOUS HIGH AMPLITUDE PATTERN TO A MORE ZONAL ONE FOR THE BEGINNING OF THE WEEK. THE END OF THE WEEK SEES AN ATMOSPHERIC WAVE TRAIN ENTER THE STATES FOR A CHANGE BACK TO A HIGHER AMPLITUDE PATTERN. OUR REGION SHOULD SEE DIURNAL SHOWERS TOWARDS THE END OF THE WEEK AS THE FLOW IS STILL A COOLING FLOW COMING IN FROM CANADA. DAILIES... MONDAY THROUGH WEDNESDAY...CONTINUING DRY AIR AND COOL TEMPERATURE ANOMALIES OVER THE REGION WITH FLOW IN FROM THE NORTHWEST BEHIND THE SLOWLY DEPARTING UPPER LEVEL LOW. THIS ALLOWS HIGH PRESSURE TO MOVE INTO THE REGION FOR LATE MONDAY THROUGH LATE WEDNESDAY. MAY ALSO SEEN EARLY MORNING FOG DURING THIS PERIOD WITH TD DEPRESSIONS LESS THAN 5F. THURSDAY THROUGH SATURDAY...PERIODS OF COOLING NIGHT TIME TEMPERATURES AND WARMING DAY TIME TEMPERATURES ALLOW FOR DIURNAL SHOWERS IN THE AFTERNOON. A LACK OF CAPE AND SHEAR DURING THIS PERIOD ALLUDES TO JUST SHOWERS RATHER THAN THUNDER. HOWEVER...WITH BUILDING HIGH PRESSURE OVER THE SOUTHEASTERN STATES...BELIEVE WEAK SHORTWAVES WILL BEGIN TO MOVE TOWARDS NEW ENGLAND. TT/S ALSO BEGIN TO INCREASE TO ABOVE 40 ON FRIDAY SHOWING INCREASING MID LEVEL MOISTURE. PRECIP AMOUNTS LOOK VERY MINIMAL DURING THIS PERIOD WITH PWATS BASICALLY NORMAL. HOWEVER MID LEVEL LAPSE RATES ABOVE 6C/KM MAY HELP KEEP STORMS GOING. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...THROUGH SUNDAY NIGHT... TONIGHT...MODERATE CONFIDENCE. SCATTERED SHOWERS POSSIBLE AFTER 06Z FROM WEST TO EAST WITH A SECONDARY AREA OF SHOWERS POSSIBLE CAPE/ISLANDS. LOW RISK OF MVFR CIGS WITH SHOWERS. VERY LOW PROBABILITY OF ISOLATED -TSRA OVER THE SOUTH COAST. SW WINDS CONTINUE. SUNDAY...SOME UNCERTAINTY REGARDING TIMING OF SHOWERS/ISOLD TSTMS. APPEARS BEST CHANCE WILL BE IN THE MORNING AND EARLY AFTERNOON MAINLY ACROSS RI AND EASTERN MA...WITH LOWER CHANCES WESTWARD. SOME IMPROVEMENT DURING THE AFTERNOON FROM WEST TO EAST AS FRONT EXITS THE REGION. MAINLY VFR WITH SCATTERED MVFR CONDITIONS IN SHOWERS AND POSSIBLY ISOLATED -TSRA ACROSS RI AND EASTERN MA 12Z- 20Z. SUNDAY NIGHT...VFR. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. LOWER CONFIDENCE IN TIMING OF ISOLATED TSRA/SHRA. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...MONDAY THROUGH THURSDAY... MONDAY...HIGH CONFIDENCE. VFR. POSSIBLE SEA BREEZES ALONG THE COASTLINES. TUESDAY...MODERATE CONFIDENCE. VFR EXCEPT LOCAL MVFR CONDITIONS ACROSS THE SOUTH COAST IN SCATTERED SHOWERS. WEDNESDAY...MODERATE CONFIDENCE. VFR. THURSDAY...MODERATE CONFIDENCE. VFR EXCEPT FOR ANY DIURNAL SHOWERS WHERE MVFR IS POSSIBLE. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. HIGH CONFIDENCE. MOSTLY QUIET BOATING WEATHER IS EXPECTED DURING THE DAY. THERE IS A LOW PROBABILITY OF SCATTERED SHOWERS TONIGHT INTO SUNDAY MORNING. SOUTHWESTERLY WINDS ARE EXPECTED THROUGH SUNDAY AFTERNOON. A COLD FRONT WILL MOVE ACROSS THE WATERS LATE SUNDAY AFTERNOON...SHIFTING WINDS FROM THE SOUTHWEST TO THE WEST. OUTLOOK...MONDAY THROUGH THURSDAY...HIGH CONFIDENCE. MONDAY THROUGH THURSDAY...WINDS AND SEAS BELOW SCA CRITERIA. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...RLG/99 NEAR TERM...KJC/NOCERA/RLG SHORT TERM...RLG LONG TERM...99 AVIATION...KJC/RLG/99 MARINE...RLG/99

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