Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 131332 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 930 AM EDT SUN JUL 13 2014 .SYNOPSIS... DRY/PLEASANT WEATHER LINGERS ACROSS MUCH OF SOUTHERN NEW ENGLAND TODAY...ALTHOUGH BREEZY CONDITIONS DEVELOP. SHOWERS AND ISOLATED THUNDERSTORMS WILL ENTER WESTERN NEW ENGLAND LATE TODAY AND THEN INTO EASTERN MA AND RI TONIGHT. A FRONTAL BOUNDARY WILL STALL ACROSS THE REGION MONDAY THROUGH WEDNESDAY YIELDING NUMEROUS SHOWERS AND THUNDERSTORMS. A FEW STORMS MAY BE STRONG ESPECIALLY MONDAY WITH THE THREAT OF FLASH FLOODING INTO WED. A TREND TOWARD DRIER AND SOMEWHAT LESS HUMID WEATHER FOLLOWS LATE IN THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 930 AM UPDATE... HIGH PRESSURE TO OUR EAST WILL ALLOW LOW LEVEL MOISTURE TO CONTINUE TO WORK INTO OUR REGION THROUGH THE AFTERNOON. WHILE WE WILL NOT BE DEALING WITH OPPRESSIVE HUMIDITY...IT WILL BE MORE HUMID THAN THE LAST FEW DAYS. EXPECT A MIXTURE OF SUN AND CLOUDS...BUT MAY SEE MORE IN THE WAY OF CLOUDS ACROSS THE INTERIOR DURING THE AFTERNOON. HIGH TEMPS WILL MAINLY BE IN THE MIDDLE TO UPPER 80S...EXCEPT COOLER ON THE IMMEDIATE SOUTH COAST/CAPE/ISLANDS. AS FOR CONVECTIVE POTENTIAL...MOST OF THE REGION WILL REMAIN DRY THROUGH THE AFTERNOON AS BETTER INSTABILITY/FORCING WILL REMAIN TO THE WEST OF OUR REGION. THE EXCEPTION WILL BE SOUTHWEST NH/WESTERN MA/NORTHERN CT...WHERE MARGINAL INSTABILITY WITH 500 J/KG OF CAPE WILL COMBINED WITH 0 TO 6 KM SHEAR OF 25 TO 30 KNOTS. SOME GUIDANCE SHOWING THE POTENTIAL FOR A FEW THUNDERSTORMS IN THIS REGION AFTER 4 PM. IN ADDITION...A LINE OF STORMS WILL MOVE MOVING OUT OF NEW YORK STATE EARLY THIS EVENING. SOME MESOSCALE MODELS SHOW IT MAY TRY TO WORK INTO WESTERN MA/SOUTHWEST NH AFTER 6 OR 7 PM. HOWEVER...IT SHOULD BE WEAKENING AS IT TRIES TO ENTER OUR WESTERN ZONES WITH LIMITED INSTABILITY. WHILE WE CAN/T RULE OUT AN STRONG STORM OR TWO ACROSS OUR FAR WESTERN ZONES WITH GUSTY WINDS...THAT IS PROBABLY THE WORST CASE SCENARIO. BRIEF HEAVY RAIN WILL ALSO BE A POSSIBILITY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... TONIGHT... UPPER LEVEL TROUGH WILL CONTINUE TO DOMINATE OVER THE GREAT LAKES REGION TONIGHT. THIS WILL ALLOW FOR AN INCREASE IN LOW LEVEL MOISTURE AS WELL AS WITH BETTER JET DYNAMICS...THE THREAT FOR SCATTERED SHOWERS/THUNDERSTORMS WILL INCREASE AS THE NIGHT WEARS ON. GIVEN PWATS ON THE ORDER OF 2+ INCHES...LOCALLY HEAVY RAINFALL WILL ALSO BE AN INCREASING CONCERN. IT WILL BE MUGGY WITH LOW TEMPS ONLY BOTTOMING OUT IN THE UPPER 60S TO LOWER 70S. TOMORROW... FIRST WAVE OF HEAVY RAINFALL SHOULD EXIT THE REGION EARLY MONDAY MORNING BEFORE ANOTHER ROUND APPROACHES BY THE LATE AFTERNOON. THERE COULD BE A BREAK IN PRECIP DURING THE DAY AND IN FACT CROSS SECTIONS ARE SHOWING A BRIEF BREAK IN MOISTURE/RH AT THE MID-LEVELS WHICH MAY ALLOW FOR BREAKS IN THE CLOUD COVER. THIS WILL HELP INCREASE DIURNAL HEATING AND SUCH THE POTENTIAL FOR STRONG/SEVERE THUNDERSTORMS. ASIDE...ANOMALOUS LOW WILL SET UP OVER THE GREAT LAKES PUSHING THE TROUGH AXIS OVER THE MIDWEST KEEPING SNE IN THE SOUTHWEST FLOW. THIS WILL CONTINUE TO INCREASE THE MOISTURE PROFILES AS DEWPOINTS REACH ABOVE 70F. ANOTHER SHORTWAVE WILL RIDE THROUGH THE FLOW ON MONDAY SPARKING OFF ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS. BELIEVE AREAL COVERAGE WILL BE MORE THEN SUNDAY...ALTHOUGH A FEW OF THE HI- RES GUIDANCE SHOWS MORE OF AN ISOLATED COVERAGE. HOWEVER MANY OF THE SYNOPTIC MODELS SHOW QPF AND WITH THE AMOUNT OF LIFT AND MOISTURE IN THE PROFILE BELIEVE COVERAGE WILL BE MORE SCT/WIDESPREAD. CAPE VALUES WILL INCREASE BETWEEN 1500-2000 J/KG AND WITH 0-6 KM BULK SHEAR VALUES REACHING 45 KTS...COULD SEE STRONG AND PERHAPS SEVERE WEATHER WITH DAMAGING WINDS AND HEAVY RAINFALL BEING THE MAIN THREATS. AS DEWPOINTS WILL REACH INTO THE 70S...CANNOT RULE OUT THE POTENTIAL FOR A QUICK SPIN-UP IN THIS SOMEWHAT TROPICAL AIRMASS AS WELL AS 0-1 KM SHEAR VALUES NEAR 20-25KTS. KEEP AN EYE TO THE SKY AND STAY TUNED FOR UPDATES TO THE FORECAST AS THE SEVERE WEATHER POTENTIAL CAN CHANGE. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... HIGHLIGHTS... * NUMEROUS SHOWERS & THUNDERSTORMS MON NGT INTO WED WITH HEAVY RAIN AND ISOLATED FLASH FLOOD POTENTIAL * WARM AND VERY HUMID MON NIGHT AND TUESDAY * IMPROVING WEATHER WITH DRIER AND LESS HUMID CONDITIONS THU AND FRI ENSEMBLES AND DETERMINISTIC GUIDANCE CONTINUE TO SUPPORT A HIGH AMPLITUDE PATTERN ACROSS NORTH AMERICA WITH AN ANOMALOUS TROUGH OF -3 SD /500 MB HEIGHTS/ DIVING INTO THE GREAT LAKES MON. THIS TROUGH WILL BE SLOW MOVING AS DOWNSTREAM RIDGING DEVELOPS OVER THE NORTHWEST ATLC. THE SLOW MOVEMENT OF THIS TROUGH WILL RESULT IN A STALLED FRONTAL BOUNDARY ACROSS NEW ENGLAND FROM SUN NIGHT INTO WED. THE HIGH AMPLITUDE PATTERN ALSO RESULTS IN MERIDIONAL FLOW ALONG THE EASTERN SEABOARD WITH PWATS UP TO +2 SD STREAMING POLEWARD INTO NEW ENGLAND FROM SUN NIGHT INTO WED. THIS DURATION COUPLED WITH DEEP UNIDIRECTIONAL FLOW WILL PROVIDE AN ENVIRONMENT FAVORABLE FOR BACK BUILDING AND TRAINING CELLS. THUS A RISK FOR ISOLATED FLASH FLOODING. BOTH 00Z EC AND GFS CONTINUE TO OFFER HEAVY QPF WITH 1-3" ACROSS THE REGION FROM TONIGHT THRU WED. 00Z GEFS ENSEMBLES NOT AS BULLISH WITH VERY LOW PROBS OF 2+ INCHES. IN ADDITION...THIS HIGH AMPLITUDE PATTERN YIELDS AN ANOMALOUS /+2 SD/ UPPER LEVEL JET STREAK ACROSS THE NORTHEAST AND SOUTHEAST CANADA. THESE STRONG WIND FIELDS COUPLED WITH MODEST INSTABILITY WILL PROVIDE A LOW RISK OF A FEW STRONG TSTMS. AS FOR GUIDANCE ASSESSMENT...THE 00Z GFS AND GEFS HAS FINALLY COME AROUND TO THE SLOWER SOLUTIONS OF THE ECMWF AND ECENS. THE HIGHER RES OPERATIONAL RUNS OF THE ECMWF AND GFS ARE IN GOOD AGREEMENT THAT A WAVE WILL TRACK UP THE FRONT TUE NIGHT INTO WED. THIS WILL SLOW THE FRONT/S DEPARTURE AND LIKELY KEEP SHOWERS/TSTMS IN THE FORECAST AT LEAST THRU EARLY WED. THIS FRONTAL WAVE WILL ALSO ENHANCE THE RISK FOR HEAVY RAIN AND ASSOCIATED FLASH FLOODING. MODELS THEN MOVE THE FRONT OFFSHORE LATE WED/WED NIGHT ALONG WITH MID/UPPER LEVEL TROUGH DEAMPLIFYING. THIS SUPPORTS A TREND TOWARD DRIER AND LESS HUMID WEATHER THU AND FRI. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH MONDAY/... 7 AM UPDATE...NO MAJOR CHANGES FROM 06Z TAFS. GUSTY SSW WINDS DEVELOP AROUND 15Z WITH GUSTS UP TO 25 KT OR SO THIS AFTERNOON. EARLIER DISCUSSION BELOW. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TODAY...HIGH CONFIDENCE IN MAINLY VFR CONDITIONS. GUSTY SOUTHERLY WINDS BETWEEN 20-30 KTS. A FEW SHOWERS/THUNDERSTORMS MAY IMPACT WESTERN SITES LATE THIS AFTERNOON...RESULTING IN LOCALIZED LOWER CONDITIONS. HOWEVER...THIS ACTIVITY WILL LIKELY REMAIN WEST OF ALL OUR FORECAST TERMINALS FOR MOST OF THE DAY. TONIGHT...MODERATE CONFIDENCE. MVFR-IFR CIGS/VSBYS OVER SPREAD THE REGION AS DEEP LOW LEVEL MOISTURE WORKS INTO THE REGION. THE RISK FOR SCATTERED SHOWERS/THUNDERSTORMS INCREASES THROUGH THE OVERNIGHT HOURS. TOMORROW...MODERATE CONFIDENCE. VFR/MVFR CONDITIONS THROUGHOUT THE DAY DROPPING TO MVFR/IFR IN SCATTERED SHOWERS/THUNDERSTORMS. A FEW OF THESE THUNDERSTORMS MAY PRODUCE VERY STRONG WINDS. KBOS TAF...HIGH CONFIDENCE IN TAF. KBDL TAF...HIGH CONFIDENCE IN TAF. LOW PROB OF ISOLATED SHOWER/THUNDERSTORM AFTER 21Z. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY... MONDAY NIGHT AND TUESDAY...NUMEROUS SHOWERS AND SCATTERED TSTMS WITH HEAVY DOWNPOURS LIKELY. PATCHY FOG AT NIGHT LIKELY YIELDING MVFR/IFR CONDITIONS...THEN LIFTING TO MARGINAL VFR DURING THE LATE MORNING AND AFTERNOON. MODERATE TO HIGH CONFIDENCE. WEDNESDAY...IFR/MVFR EASTERN MA AND RI WITH VFR/MVFR WESTERN CT/MA. GREATEST RISK OF SHOWER/TSTMS AND PATCHY FOG ACROSS RI AND EASTERN MA. MODERATE CONFIDENCE. THURSDAY...TREND TOWARD VFR ALONG WITH DRY WEATHER. MODERATE CONFIDENCE. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...HIGH CONFIDENCE. TODAY AND TONIGHT...INCREASING SOUTHWEST FLOW AND GOOD MIXING OVER THE LAND SHOULD ALLOW SOUTHWEST WIND GUSTS OF 25 TO 30 KNOTS TO DEVELOP LATE THIS MORNING AND PARTICULARLY DURING THE AFTERNOON HOURS ACROSS THE NEAR SHORE WATERS. LONG SOUTHWEST FETCH SHOULD ALLOW SCA SEAS TO DEVELOP ON THE OUTER-WATERS TONIGHT. THEREFORE...SCA HEADLINES POSTED FOR ALL WATERS FOR THE ABOVE CONCERNS. IN ADDITION...SOME FOG MAY DEVELOP SUNDAY NIGHT AND WE CAN/T RULE OUT A FEW THUNDERSTORMS PARTICULARLY TOWARD DAYBREAK MONDAY. MONDAY...SCA HAS BEEN EXTENDED FOR THE OUTER WATERS AS SEAS WILL STILL BE ABOVE 5 FT. MAIN CONCERN IS THE POTENTIAL FOR THUNDERSTORMS BY THE AFTERNOON/EVENING HOURS. SOME OF THESE STORMS COULD BE STRONG/SEVERE. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY... MONDAY NIGHT-TUESDAY...COLD FRONT REMAINS WEST OF NEW ENGLAND WATERS. THUS SSW WINDS 15-20 KT CONTINUES WITH GUSTS UP TO 25 KT POSSIBLE. SCATTERED TSTMS WITH TORRENTIAL DOWNPOURS. LOW RISK OF A TSTM WITH STRONG WINDS. VSBY REDUCED AT TIMES IN PATCHY FOG. MODERATE TO HIGH FORECAST CONFIDENCE. WEDNESDAY...TRANSITION DAY WITH FRONT SLOWLY MOVING ACROSS NEW ENGLAND AND THE COASTAL WATERS. HEAVY SHOWERS AND SCATTERED TSTMS CONTINUE ALONG WITH PATCHY MORNING FOG. HOWEVER COULD SEE SOME IMPROVEMENT LATE IN THE DAY AND ESPECIALLY AT NIGHT AS FRONT CONTINUES TO MOVE EAST. SSW WINDS 15-20 KT WILL SLACKEN AND BECOME WSW LATE OR AT NIGHT. MODERATE CONFIDENCE. THURSDAY...BIG IMPROVEMENT WITH DRIER WEATHER AND IMPROVING VSBY. FAIRLY LIGHT WINDS EXPECTED. && .TIDES/COASTAL FLOODING... VERY HIGH ASTRONOMICAL HIGH TIDES WITH BOSTON AT 12.2 FEET AROUND MIDNIGHT TONIGHT. HOWEVER...SOUTH TO SOUTHWEST WINDS WILL PREVENT ANY PROBLEMS ALONG THE EASTERN MA COAST. ALONG THE SOUTH COAST...WINDS WILL NOT BE STRONG ENOUGH TO CAUSE ANY ISSUES. NO COASTAL PRODUCTS ARE ANTICIPATED OVER THE NEXT 36 HOURS. WORST CASE SCENARIO IS VERY MINOR SPLASH OVER WITH NO REAL IMPACTS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 11 PM EDT THIS EVENING FOR ANZ230>234-236-251. SMALL CRAFT ADVISORY FROM 11 AM THIS MORNING TO 8 AM EDT MONDAY FOR ANZ235-237. SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 8 PM EDT MONDAY FOR ANZ250. SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING TO 8 PM EDT MONDAY FOR ANZ254>256. && $$ SYNOPSIS...NOCERA/DUNTEN NEAR TERM...FRANK SHORT TERM...DUNTEN LONG TERM...NOCERA AVIATION...NOCERA/DUNTEN MARINE...NOCERA/DUNTEN TIDES/COASTAL FLOODING...STAFF

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