Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 122338 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 738 PM EDT SAT JUL 12 2014 .SYNOPSIS... SCATTERED SHOWERS/THUNDERSTORMS WILL DEVELOP SUNDAY AFTERNOON ACROSS FAR WESTERN NEW ENGLAND...SLOWLY MOVING ACROSS THE REST OF THE REGION BY MONDAY. THE RAINFALL CHANCES COULD CONTINUE INTO EARLY WEDNESDAY. SOME OF THE STORMS MAY BE STRONG TO SEVERE ALONG WITH A LOCALIZED FLASH FLOOD THREAT. A TREND TOWARD DRIER AND SOMEWHAT LESS HUMID WEATHER FOLLOWS BY LATE IN THE WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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A COUPLE OF BRIEF SHOWERS DEVELOPED ALONG THE NH/MA BORDER S OF KEENE BUT WEAKENED AS THEY MOVED E INTO DRIER AIR. FAIR WEATHER CLOUDS THAT DEVELOPED THIS AFTERNOON ARE TENDING TO DISSIPATE... WHILE COASTAL AREAS CLEARED OUT BEHIND SEA BREEZE FRONTS. SOME CLOUDS ARE LEFT OVER ACROSS THE BERKSHIRES AND CENTRAL AND NORTHERN CT VALLEY AT 23Z. EXPECT SKIES TO BECOME MAINLY CLEAR EARLY...BUT SOME MID AND HIGH CLOUDS WILL FILTER IN AROUND OR AFTER MIDNIGHT...MOVING E OUT OF W NY/PA. HAVE UPDATED GRIDS TO BRING CONDITIONS CURRENT. PREVIOUS DISCUSSION... HIGH PRESSURE CONTINUES TO MOVE OFF THE COAST ALLOWING LOW LEVEL MOISTURE TO GRADUALLY RETURN TO THE REGION. THEREFORE...LOWS WILL ONLY BOTTOM OUT TO BETWEEN 60 AND 65 ACROSS MOST LOCALES BY DAYBREAK SUNDAY. SOME PATCHY FOG MAY DEVELOP IN SOME TYPICALLY PRONE LOCATIONS LATE...BUT NOTHING WIDESPREAD.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... SUNDAY... ANOMALOUS CLOSED UPPER LEVEL LOW WILL DROP SOUTH TOWARDS GREAT LAKES. HOWEVER...DYNAMICS/FORCING WILL STILL BE FAR ENOUGH WEST TO RESULT IN ONE MORE DRY DAY ACROSS MUCH OF OUR REGION. THE EXCEPTION WILL BE SOUTHWEST NH/WESTERN MA AND NORTHERN CT...AS THESE LOCATIONS WILL BE ON THE EDGE OF THE INSTABILITY AXIS. CAPES ON THE ORDER OF 500 J/KG ALONG WITH 25 TO 30 KNOTS OF SHEAR WILL BE ENOUGH TO TRIGGER A FEW SHOWERS/THUNDERSTORMS. NOW WERE CERTAINLY NOT EXPECTING A WASHOUT IN THIS REGION...BUT A FEW HIT AND MISS SHOWERS/STORMS POSSIBLE MAINLY DURING THE AFTERNOON HOURS. INSTABILITY/SHEAR COMBINATION DOES NOT LOOK TO BE ENOUGH FOR ANY SEVERE WEATHER...ALTHOUGH CAN/T RULE OUT AN ISOLATED STRONG THUNDERSTORM. BEST SHOT FOR THAT WILL BE ALONG THE EAST SLOPES OF THE BERKSHIRES. HIGH TEMPS WILL BE IN THE MIDDLE TO UPPER 80S...EXCEPT A FEW DEGREES COOLER ON THE IMMEDIATE SOUTH COAST/CAPE/ISLANDS. IT WILL BE MORE HUMID THAN THE LAST FEW DAYS...BUT NOT OPPRESSIVE. SUNDAY NIGHT... INCREASING LOW LEVEL MOISTURE AND DECENT JET DYNAMICS IN ASSOCIATION CLOSED LOW OVER THE GREAT LAKES WILL ALLOW THE THREAT FOR SCATTERED SHOWERS/THUNDERSTORMS TO 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. && .LONG TERM /MONDAY THROUGH SATURDAY/... HIGHLIGHTS... * SHOWERS AND THUNDERSTORMS LIKELY MONDAY AND TUESDAY...STRONG STORMS POSSIBLE ALONG WITH A THREAT FOR FLASH FLOODING * UNSETTLED CONDITIONS MAY LINGER INTO WEDNESDAY...SLOW IMPROVEMENT PUSHES IN LATE * DRIER AND LESS HUMID WEATHER RETURNS THURSDAY AND FRIDAY OVERVIEW AND MODEL PREFERENCES... MEDIUM RANGE MODELS AND THEIR ENSEMBLES CONTINUE TO SHOW AMPLIFICATION OF MID TO UPPER LEVEL PATTERN ACROSS THE W PAC AND LOWER 48. ANOMALOUS COLD POOL MOVES ACROSS CENTRAL AND EASTERN CANADA WHILE RIDGING BUILDS ACROSS THE WESTERN U.S. INTO THE MIDDLE OF NEXT WEEK. POSITIONING OF THIS UPPER LEVEL CUTOFF SYSTEM AND SURFACE FRONT LYING ACROSS THE NORTHEAST U.S. TO THE MID ATLC STATES APPEARS TO SHOW RELATIVELY GOOD CONTINUITY...TAPPING TROPICAL AIRMASS FROM THE GULF OF MEXICO. THIS WILL YIELD CONTINUED THREAT OF FLASH FLOODING MONDAY AND TUESDAY DUE TO SLOW MOVEMENT OF THE FRONT AND TRAINING OF RAINFALL ALONG IT. COULD ALSO SEE SOME STRONG TO POSSIBLY SEVERE STORMS WITH GOOD INSTABILITY WITH SW FLOW IN PLACE AND INCREASING DEWPTS. MODELS AND ENSEMBLES DIVERGE ON THE PROGRESSION...OR LACK THEREOF... OF NORTHERN STREAM SYSTEMS DURING WEDNESDAY. 12Z GFS OP RUN CONTINUES ITS FASTER PROGRESSION THOUGH SLOWING THE PROGRESSION OF THE FRONT SOMEWHAT...AND THE 12Z GGEM OP RUN IS ALSO CLOSER TO THIS SOLUTION. HOWEVER...BOTH THE 00Z AND 12Z EC RUN ARE SLOWER AS ONE WOULD EXPECT WITH MERIDIONAL UPPER LEVEL PATTERN. PLAN ON LEANING TOWARD A BLEND OF AVAILABLE MODELS AND ENSEMBLES DUE TO UNCERTAINTY OF TIMING THIS FAR OUT. LOOKS LIKE THE UPPER CUTOFF TENDS TO RETREAT INTO EASTERN CANADA LATE NEXT WEEK WITH FLATTENING OF THE UPPER FLOW. CONDITIONS LOOK DRIER WITH SEASONABLE TEMPERATURES. DETAILS... MONDAY THROUGH TUESDAY...BROAD H5 TROUGH ACROSS THE GREAT LAKES WILL SET UP A SW WIND FLOW AT THE SURFACE AND ALOFT. THIS WILL OPEN THE TROPICAL CONNECTION FROM THE GULF OF MEXICO AS THE FRONT RUNS PARALLEL TO THE UPPER FLOW. PWATS INCREASE TO 2.1 TO 2.2 INCHES... AROUND 2 SD ABOVE NORMAL FOR MID JULY...DURING THIS TIMEFRAME. HIGHEST CONCERN IS THE POTENTIAL OF FLASH FLOODING WITH EXCELLENT MOISTURE TRANSPORT AT ALL LEVELS...ESPECIALLY AS WEAK SHORT WAVES MOVE ALONG THE SLOW MOVING FRONT. QPF FORECAST CONTINUES TO SIGNAL AVERAGE RAINFALL OF 1-3 INCHES...HIGHEST ACROSS W CT AND MA. SOME SPOTS COULD RECEIVE MORE IN LOCALIZED HEAVY DOWNPOURS OR IF TRAINING OF HEAVY CELLS MOVE ACROSS. CONTINUED MODERATE RISK FOR HEAVY RAINFALL AND LOCALIZED FLOODING. ALSO SEE POTENTIAL FOR STRONG TO POSSIBLY SEVERE TSTMS DURING THIS TIMEFRAME...BUT LOOKS LIKE BEST SHOT OCCURS DURING TUESDAY. GOOD JET DYNAMICS IN PLACE WITH RRQ OF A 120 KT H3 JET PASSES ACROSS QUEBEC ON TUESDAY. ALSO NOTING K INDICES IN THE MID TO UPPER 30S ALONG WITH LIFTED INDICES BELOW ZERO. CARRIED CHANCE TO LIKELY POPS THROUGH THIS TIMEFRAME ALONG WITH ENHANCED WORDING FOR HEAVY RAINFALL. DEWPTS WILL BE IN THE MID 60S TO AROUND 70...SO WARM AND MUGGY CONDITIONS IN PLACE. WEDNESDAY...STILL A LOT OF QUESTIONS AS TO TIMING THE FRONT ACROSS THE REGION. FOR NOW...EXPECT THE FRONT TO EVER SO SLOWLY MOVE ACROSS DURING THE DAY. WILL STILL SEE CONTINUED RISK FOR THUNDERSTORMS. EVEN THOUGH THE CORE OF 120 KT H3 JET IS IN NE QUEBEC BY THIS TIME...WILL STILL SEE SOME EFFECTS FOR EXPANSIVE RRQ OF THIS JET ACROSS INTERIOR AREAS. HAVE CARRIED CHANCE SHOWERS/TSTMS THROUGH MOST OF THE DAY...THEN SHOULD DIMINISH AROUND OR AFTER SUNSET. DEWPTS START TO DROP ACROSS SW NH/W MA BY EVENING. THURSDAY...COULD STILL SEE SOME WIDELY SCT SHOWERS ACROSS E MA THU MORNING AS FRONT CONTINUES ITS SLOW TREK OFF THE COAST. IMPROVING CONDITIONS INLAND EXPECTED...WHICH SHOULD SHIFT E DURING THE AFTERNOON. H5 TROUGH REMAINS W OF THE REGION...SO CAN NOT RULE OUT WIDELY SCT DIURNAL SHOWERS DEVELOPING ACROSS N MA/S NH WHERE COOLEST AIR ALOFT IS IN PLACE. DEWPTS DROP TO THE MID-UPPER 50S ACROSS THE CT VALLEY...BUT MAY LINGER IN THE LOWER 60S OVER EASTERN AREAS. EXPECT SEASONABLY HIGH TEMPS. FRIDAY-SATURDAY...MODELS CONTINUE TO SIGNAL DEAMPLIFICATION OF THE UPPER TROUGH TO THE W...BUT RATHER LOW CONFIDENCE DURING THIS PORTION OF THE FORECAST DUE TO PREVIOUS TIMING ISSUES. SHOULD BE DRY AND COMFORTABLE ON FRIDAY...WITH DEWPTS CREEPING UP AGAIN DURING SATURDAY. VERY LOW PROB OF A DIURNAL SHOWER WELL INLAND. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/...
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FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH SUNDAY NIGHT/... TONIGHT...HIGH CONFIDENCE. VFR. PERHAPS A TOUCH OF VERY LATE NIGHT/EARLY SUN MORNING PATCHY GROUND FOG IN THE TYPICALLY PRONE LOCATIONS. SEA BREEZES WILL COME TO AN END BY 02Z. SUNDAY...HIGH CONFIDENCE IN MAINLY VFR CONDITIONS. A FEW SHOWERS/THUNDERSTORMS MAY AFFECT OUR FAR WESTERN ZONES MAINLY IN THE AFTERNOON...RESULTING IN LOCALIZED LOWER CONDITIONS. HOWEVER...THIS ACTIVITY WILL LIKELY REMAIN WEST OF ALL OUR FORECAST TERMINALS FOR MOST OF THE DAY. SUNDAY NIGHT...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 AS SUNDAY NIGHT WEARS ON. KBOS TAF...HIGH CONFIDENCE IN TAF. EASTERLY SEA BREEZE BECOMES SOUTHEAST THROUGH LATE AFTERNOON AND THEN FINALLY SOUTH BY 00Z THIS EVENING. KBDL TAF...HIGH CONFIDENCE IN TAF. OUTLOOK...MONDAY THROUGH THURSDAY... MONDAY AND TUESDAY...MODERATE TO HIGH CONFIDENCE. MVFR-IFR CIGS/VSBYS AT NIGHT IN AREAS OF FOG ALONG WITH SCATTERED SHOWERS/TSTMS. CONDITIONS MAY IMPROVE TO LOW END VFR DURING THE AFTERNOON HOURS. EXPECT SHOWERS AND SCT TSTMS ANYTIME DURING THIS TIMEFRAME. WEDNESDAY...LOW CONFIDENCE DUE TO TIMING. MVFR CONDITIONS TO START...THEN SLOW IMPROVEMENT FROM NW-SE. CONDITIONS APPEAR TO LINGER ACROSS E MA/RI THROUGH MOST OF DAY. PATCHY LATE NIGHT/EARLY MORNING FOG WITH LOCAL IFR CONDITIONS. THURSDAY...LOW CONFIDENCE DUE TO TIMING. MAY SEE LOCAL MVFR CONDITIONS ACROSS E COASTAL MA EARLY WITH ANY LEFTOVER SHOWERS...OTHERWISE VFR.
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&& .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. TONIGHT...WINDS/SEAS TO REMAIN WELL BELOW SCA THRESHOLDS. SUNDAY AND SUNDAY NIGHT...INCREASING SOUTHWEST FLOW AND GOOD MIXING OVER THE LAND SHOULD ALLOW SOUTHWEST WIND GUSTS OF 25 TO 30 KNOTS TO DEVELOP LATE SUNDAY MORNING AND PARTICULARLY DURING THE AFTERNOON ACROSS THE NEAR SHORE WATERS. IN ADDITION...LONG SOUTHWEST FETCH SHOULD ALLOW SCA SEAS TO DEVELOP ON THE OUTER-WATERS SUNDAY NIGHT. 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. OUTLOOK...MONDAY THROUGH THURSDAY... MONDAY-TUESDAY...MODERATE TO HIGH CONFIDENCE. EXPECT S-SW WINDS GUSTING UP TO 20 KT OVER THE OUTER WATERS...LOW PROB OF A FEW GUSTS TO 25 KT ON THE SOUTHERN OUTER WATERS. SMALL CRAFT SEAS WILL LIKELY CONTINUE...UP TO 5-6 FT ON THE OUTER WATERS. REDUCED VSBYS IN AREAS OF FOG. SHOWERS/SCT TSTMS THROUGH THIS PERIOD. WEDNESDAY...MODERATE CONFIDENCE. SW WINDS AND SEAS DIMINISH. STILL CHANCE FOR SCT SHOWERS/TSTMS AND PATCHY FOG REDUCING VSBYS. THURSDAY...MODERATE CONFIDENCE. WINDS AND SEAS BELOW SMALL CRAFT CRITERIA. LEFTOVER PATCHY FOG WITH REDUCED VSBYS EARLY THU MORNING. && .TIDES/COASTAL FLOODING... VERY HIGH ASTRONOMICAL HIGH TIDES WITH BOSTON AT 12.0 FEET JUST BEFORE MIDNIGHT AND THEN 12.2 FEET AROUND MIDNIGHT SUNDAY NIGHT. 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. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 11 AM TO 11 PM EDT SUNDAY FOR ANZ230>234-236-251. SMALL CRAFT ADVISORY FROM 11 AM SUNDAY TO 8 AM EDT MONDAY FOR ANZ235-237. SMALL CRAFT ADVISORY FROM 2 PM SUNDAY TO 8 AM EDT MONDAY FOR ANZ250. SMALL CRAFT ADVISORY FROM 11 PM SUNDAY TO 8 AM EDT MONDAY FOR ANZ254>256. && $$ SYNOPSIS...FRANK/EVT NEAR TERM...FRANK/EVT SHORT TERM...FRANK LONG TERM...EVT AVIATION...FRANK/EVT MARINE...FRANK/EVT TIDES/COASTAL FLOODING...STAFF

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