Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 012010 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 410 PM EDT WED OCT 1 2014 .SYNOPSIS... THE COOL...WET WEATHER CONTINUES INTO EARLY THURSDAY. HIGH PRESSURE BEGINS TO BRING DRY AIR BACK IN LATE TOMORROW INTO FRIDAY. A FRONTAL SYSTEM WILL BRING A PERIOD OF RAIN SATURDAY INTO SATURDAY EVENING...FOLLOWED BY COOLER WEATHER SUNDAY. TEMPERATURES MODERATE EARLY NEXT WEEK WITH A CHANCE OF SHOWERS TUESDAY AS ANOTHER FRONT APPROACHES. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... SLOW DEVELOPMENT OF A HANGING TROWAL FORMATION ACROSS THE REGION LATE THIS AFTERNOON. THIS COMBINED WITH UPPER LVL CUTOFF MEANDERING ALONG THE S COASTAL REGION CONTINUES TO COMBINE WITH MOIST COLUMN /PWATS LOCALLY EXCEED 1.5 INCHES/ CONTINUES TO YIELD BANDS OF RAINFALL STRETCHING ACROSS THE WHOLE BOX CWA. THE NE FLOW CONTINUES TOO...STREAMING IN PLENTY OF MARINE MOISTURE FROM THE GULF OF MAINE. THIS TROWAL/SFC INVERTED TROF FEATURE WILL BE DEFINING THE OVERNIGHT WX. ALREADY WE ARE SEEING THE DEVELOPMENT OF CONVECTION IN THE VICINITY OF ACK WHERE A MODEST AXIS OF UPPER LVL INSTABILITY DEFINED BY A DRY SLOT ALONG THE UPPER CUTOFF EXISTS. ALTHOUGH SOUNDINGS SUGGEST MOST OF THIS IS ELEVATED IT IS ENOUGH TO INITIATE LOCALLY HEAVY CONVECTIVE ELEMENTS. THIS IS ALSO ALONG A SLOWLY INCREASING ELY LLJ...WHICH IS EXPECTED TO INCREASE TO AROUND 40-45 KT AT H92 BETWEEN 00Z AND 06Z THIS EVENING. THE COMBINATION OF THIS MOISTURE /PWATS NEARLY 2 STD DEVIATIONS ABOVE NORMAL/ THE ROBUST LLJ AND MODEST ELEVATED INSTABILITY UNDER THE SLOWLY ERD MOVING CUTOFF ALL SUGGEST THAT POCKETS OF HEAVY RAINFALL ARE LIKELY SOMEWHERE IN AROUND SE MA. 12Z GUIDANCE ALL NOW GENERALLY AGREE ON A LOCALLY HIGH QPF BULLSEYE ALTHOUGH WITH SOME DISAGREEMENT AND CONVECTIVE FEEDBACK APPARENT. THE POSSIBILITY THAT SOME MESO-SCALE GUIDANCE SHOWS THESE CONVECTIVE ELEMENTS CONTINUING/INCREASING OVERNIGHT HAS LED TO THE ISSUANCE OF A FLOOD WATCH FOR SOUTHEAST MA...WHERE POCKETS OF TOTAL RAINFALL COULD QUICKLY EXCEED 3 INCHES IN SPOTS /SEE HYDRO SECTION BELOW/. IN FACT...REPORTS ALREADY INDICATE OVER AN INCH HAS FALLEN IN THE WATCH AREA. THE FLUX IN THE LOCATION OF THE INVERTED TROF DOES SUGGEST THAT THE AXIS COULD LIE OFFSHORE...BUT WITH THE POTENTIAL SO CLOSE AND CONVECTION ALREADY OCCURRING LATE THIS AFTERNOON...FEEL THE WATCH IS WARRANTED FOR PRIMARILY THE URBAN FLOOD THREAT. OTHERWISE...ELSEWHERE ACROSS THE REGION...PERIODIC RAINFALL IS LIKELY TO CONTINUE AS MOISTURE CONTINUES TO STREAM IN FROM THE E. ALTHOUGH DO NOTE THE INCREASE IN DRY AIR FROM THE W AS HIGH PRES ATTEMPTS TO REGAIN CONTROL. THEREFORE...BY 12Z THE FOCUS MAINLY MAY BE AWAY FROM NW MA AND SW NH. MINS REMAIN MOSTLY IN THE 50S TONIGHT. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... TOMORROW... EARLY MORNING RAINS CONTINUE ESPECIALLY ACROSS THE E HALF OF THE REGION AS SFC INVERTED TROF AND UPPER LVL CUTOFF BEGIN SLOW SHIFT OFFSHORE. DRIER AIR WILL BE ATTEMPTING TO WORK IN FROM THE W THROUGH THE DAY...HOWEVER GRADIENT FLOW REMAINS MAINLY N-NE. THEREFORE...EVEN THOUGH RAINFALL POTENTIAL WILL BE DECREASING THROUGH THE DAY...THE LOW CLOUDS/FOG MAY REMAIN AT LEAST INTO THE EARLY AFTERNOON WITH SOME CLEARING POSSIBLE...SLOWLY...FROM W TO E DURING THE AFTERNOON SUCH THAT SOME ACTUALLY MAY SEE A SUNSET. THE E SHORES MAY REMAIN SOCKED IN WITH CLOUDS MOST OF THE DAY HOWEVER...AS IT WILL TAKE UNTIL HIGH PRES BUILDS OVER AND A MODEST SUBSIDENCE INVERSION ARRIVES TO SCOUR OUT SOME OF THE LOW-MID LVL MOISTURE. HIGHS REMAIN ON THE COOL SIDE...MAINLY UPPER 50S AND LOW 60S DUE TO THIS CLOUD COVER. TOMORROW NIGHT... CONTINUED IMPROVEMENT AS HIGH PRES BEGINS TO NOSE IN FROM THE N. NOTING ENOUGH DRYING THROUGH THE COLUMN ACROSS SRN NEW ENGLAND THAT SOME MAY SEE SOME CI FILTERED STAR-LIGHT AND EVEN SOME CLEARING SKIES. WITH THE DRIER AIR MOVING IN DWPTS ARE LIKELY TO FALL BACK INTO THE 40S AND TEMPS ARE LIKELY TO HEAD THIS WAY AS WELL. THEREFORE...WITH SOME LEFTOVER GROUND MOISTURE...FOG IS LIKELY IN SOME SPOTS...AND MAY EVEN BE LOCALLY DENSE. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... HIGHLIGHTS... * A PERIOD OF RAIN LIKELY SAT INTO SAT EVENING * DRY AND COOLER SUNDAY * MODERATING TEMPS EARLY NEXT WEEK WITH NEXT CHANCE OF SHOWERS TUE OVERVIEW... MODELS ARE IN GOOD AGREEMENT WITH NEGATIVE TILT SHORTWAVE ROTATING AROUND GT LAKES LOW THIS WEEKEND AND TIMING OF A STRONG COLD FRONT LATE SAT AND SAT EVENING WHICH WILL BRING A PERIOD OF RAIN...MOST OF WHICH LOOKS TO FALL SAT AFTERNOON AND EVENING. MID LEVEL LOW LIFTS N INTO CANADA THROUGH EARLY NEXT WEEK WITH TROF SETTING UP ACROSS THE GT LAKES AND BROAD CYCLONIC SW FLOW INTO NEW ENG. MODELS DIFFER ON THE AMPLITUDE OF NEXT SHORTWAVE ROTATING AROUND THE MEAN TROF BUT BUT IT APPEARS SOME UNSETTLED WEATHER IS POSSIBLE TUESDAY. DAILIES... FRIDAY... SNE WILL BE IN BETWEEN SYSTEMS WITH HIGH PRES RIDGE ACROSS THE REGION. THE COLUMN IS MOSTLY DRY WHICH SUPPORTS MOSUNNY SKIES...BUT MODELS INDICATE LOW LEVEL MOISTURE BACKING IN FROM THE EAST WHICH MAY BRING SOME LOW CLOUDS TO CAPE/ISLANDS AND INTO E MA DURING THE AFTERNOON. THESE LOW CLOUDS ARE EXPECTED TO EXPAND WEST ACROSS MUCH OF THE REGION FRI NIGHT AND MODELS INDICATE POTENTIAL FOR SOME DRIZZLE DEVELOPING IN EASTERN NEW ENG WITH ABUNDANT LOW LEVEL MOISTURE AND NE FLOW BELOW DRIER AIR ALOFT. TEMPS FRI WILL BE IN THE 60S...COOLEST E MA COAST AND MILDEST IN THE CT VALLEY. SATURDAY INTO SATURDAY NIGHT... MODELS IN DECENT AGREEMENT ON TIMING OF THE COLD FRONT LATE SAT AND SAT EVENING ACROSS SNE...REACHING CT VALLEY BY 00Z AND OFF THE COAST BY 06Z. MODEST LOW LEVEL JET AND LOW LEVEL CONVERGENCE ALONG WITH PWAT PLUME 1.5"+ WILL BRING A PERIOD OF WIDESPREAD SHOWERS TO SNE. TIMING LOOKS TO BE MOSTLY IN THE AFTERNOON INTO THE EVENING FROM WEST TO EAST...ALTHOUGH AREAS OF DRIZZLE POSSIBLE THROUGH THE MORNING AND IT/S POSSIBLE BULK OF RAIN COULD HOLD OFF UNTIL LATE SAT FOR E COASTAL MA AND CAPE/ISLANDS. THERE IS SOME MARGINAL INSTABILITY NOTED IN THE MODELS SO CANT RULE OUT A BRIEF RUMBLE OF THUNDER OR HEAVY CONVECTIVE SHOWER AT THE NOSE OF THE LLJ...BUT SYSTEM IS PROGRESSIVE WHICH WILL LIMIT DURATION OF RAINFALL WITH RAIN EXITING THE REGION 00-06Z FROM WEST TO EAST. SUNDAY AND MONDAY... DRY AND SOMEWHAT COOLER WEATHER SUNDAY WITH MODEST WESTERLY WINDS AND MOSUNNY SKIES...THEN BREEZY AND MILDER MONDAY AS WARM AIR ADVECTION BEGINS WITH DEVELOPING SW FLOW. A BIT MORE CLOUDS POSSIBLE MONDAY...ESPECIALLY WEST ZONES AS MID LEVEL MOISTURE MOVES IN FROM THE WEST IN WARM AIR ADVECTION PATTERN. TUESDAY AND WEDNESDAY... DESPITE DIFFERENCES IN AMPLITUDE OF NEXT SHORTWAVE...GFS AND ECMWF INDICATE POTENTIAL FOR SHOWERS TUE AS SOME SORT OF BOUNDARY APPROACHES FROM THE WEST. THEN SOME DRYING ON WEDNESDAY ALTHOUGH THIS IS LOW CONFIDENCE THIS FAR OUT. SEASONABLY MILD TEMPS EXPECTED. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...TODAY THROUGH THURSDAY...MODERATE CONFIDENCE. THROUGH TONIGHT... MAINLY MIX OF IFR/MVFR IN PERIODS OF RAIN AND LOW CIGS THROUGH THE REST OF THE DAY. THE PERIODS OF RAIN CONTINUE TONIGHT...ESPECIALLY IN THE EASTERN HALF OF THE REGION. BETWEEN RAINFALL...CONDITIONS COULD BRIEFLY DIP TO LIFR AT SOME TERMINALS. ALSO...THERE IS THE THREAT FOR HEAVY RAINFALL AND EVEN A BRIEF THUNDERSHOWER FOR RI AND SE MA LATE THIS EVENING AND EARLY TOMORROW MORNING. WINDS INCREASE OUT OF THE N-NE WITH GUSTS 25-30 KT POSSIBLE AT NEAR COASTAL TERMINALS OVERNIGHT. TOMORROW INTO TOMORROW NIGHT... RAINFALL GRADUALLY COMES TO AN END WITH A SLOW LIFT FROM IFR/MVFR TO VFR FROM W TO E. SOME E LOCATIONS MAY REMAIN IFR/MVFR FOR MUCH OF THE DAY AND MAY WAIT UNTIL TOMORROW NIGHT BEFORE FULLY BREAKING OUT. HOWEVER...THE OVERALL TREND IS EXPECTED TO BE FOR IMPROVEMENT. KBOS...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN TIMING. KBDL...HIGH CONFIDENCE IN TRENDS...LOWER CONFIDENCE IN TIMING. OUTLOOK...FRIDAY THROUGH MONDAY... FRIDAY...MODERATE CONFIDENCE. MOSTLY VFR...BUT MVFR CIGS MAY BACK IN FROM THE OCEAN INTO E COASTAL MA AND CAPE/ISLANDS FRI AFTERNOON. EXPECT CIGS LOWERING TO IFR FRI NIGHT AND EXPANDING WEST ACROSS THE REGION WITH PATCHY FOG AND DRIZZLE POSSIBLE. SATURDAY...MODERATE CONFIDENCE. WIDESPREAD MVFR/IFR CIGS EXPECTED. PATCHY DRIZZLE IN THE MORNING...THEN SHOWERS WILL MOVE WEST TO EAST ACROSS SNE SAT AFTERNOON AND EVENING AHEAD OF A COLD FRONT. SOUTH WINDS SAT SHIFTING TO WEST SAT NIGHT. SUNDAY AND MONDAY...HIGH CONFIDENCE. VFR. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...TONIGHT THROUGH TOMORROW NIGHT ...HIGH CONFIDENCE INCREASING NE WINDS ARE EXPECTED THROUGH TONIGHT INTO TOMORROW...SUCH THAT SOME WIND GUSTS AROUND 30 KT ARE POSSIBLE. NOT EVEN OUT OF THE QUESTION A BRIEF WIND GUST APPROACHES GALE FORCE IN SOME OF THE HEAVIER RAINFALL EXPECTED ESPECIALLY ALONG THE SOUTHEASTERN WATERS OF SOUTHERN NEW ENGLAND. SMALL CRAFT ADVISORIES CONTINUE...AND HAVE BEEN EXTENDED INTO TOMORROW NIGHT. EVEN THOUGH WINDS WILL BEGIN TO DROP OFF BY THEN...SWELLS APPROACHING 9 FT ARE POSSIBLE ON THE OCEAN WATERS AND THESE WILL TAKE SOME TIME TO FALL. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY...MODERATE CONFIDENCE. FRI...EXPECT DIMINISHING NE WINDS DURING THE DAY WITH SPEEDS REMAINING BELOW SCA THRESHOLDS. BUT HAZARDOUS SEAS WILL CONTINUE OVER OUTER WATERS. SATURDAY...SOUTHERLY WINDS MAY GUST UP TO 25 KT...ESPECIALLY NEARSHORE WATERS AS LOW LEVEL JET MOVES ACROSS THE WATERS. CURRENT FORECAST WINDS MAY EVENTUALLY NEED TO BE INCREASED. VSBYS WILL BE REDUCED IN AREAS OF DRIZZLE AND FOG IN THE MORNING AND SHOWERS DURING THE AFTERNOON AND EVENING. WINDS SHIFT TO WEST SAT NIGHT WITH IMPROVING VSBYS. SUNDAY...WEST WIND GUSTS COULD REACH SCA LEVELS AND HAZARDOUS SEAS WILL PERSIST. MONDAY...SW WINDS MOSTLY BELOW SCA WITH SEAS SUBSIDING BELOW 5 FT. && .HYDROLOGY... FLOOD WATCH HAS BEEN ISSUED FOR SOUTHEASTERN MASSACHUSETTS. THE ISSUE AT HAND IS THE POSSIBILITY OF LOCALLY HEAVY RAINFALL THIS EVENING AND OVERNIGHT. RAINFALL RATES OF 1-2 INCHES ARE POSSIBLE ALONG WITH FINAL STORM TOTALS OF 3-6 INCHES. THIS MAY LEAD TO URBAN/STREET AND EVEN POSSIBLY SOME BASEMENT FLOODING IN THE WATCH AREA. THERE IS SOME UNCERTAINTY IN EXACTLY WHERE THE HEAVIEST AXIS OF RAINFALL SETS UP...AS IT MAY REMAIN OFFSHORE. HOWEVER...GIVEN THE POSSIBILITY OF IT BEING FURTHER W...AND THAT HEAVY RAIN IS CURRENTLY FALLING IN THIS AREA...FEEL THE WATCH IS WARRANTED. MAY ALSO NEED TO MONITOR FOR POSSIBLE EXPANSION FURTHER W...FOR THE URBAN AREAS OF RI GIVEN THAT SOME SLIGHT WESTWARD PROGRESSION IS EVIDENT IN SOME GUIDANCE. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...FLOOD WATCH THROUGH THURSDAY MORNING FOR MAZ017>024. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT FRIDAY FOR ANZ232-235-237. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THURSDAY FOR ANZ231-233- 234. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THURSDAY FOR ANZ230. SMALL CRAFT ADVISORY UNTIL 8 AM EDT FRIDAY FOR ANZ250-251- 254>256. && $$ SYNOPSIS...KJC/DOODY NEAR TERM...DOODY SHORT TERM...DOODY LONG TERM...KJC AVIATION...KJC/DOODY MARINE...KJC/DOODY HYDROLOGY...STAFF

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