Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 142024 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 424 PM EDT MON APR 14 2014 .SYNOPSIS...
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GUSTY SOUTHERLY WINDS CONTINUE AHEAD OF A COLD FRONT THAT WILL SWEEP ACROSS THE REGION BRINGING WITH IT A SOAKING RAIN FOR TUESDAY EXITING SHORTLY AFTER MIDNIGHT WEDNESDAY. DRIER AND MUCH COOLER CONDITIONS EXPECTED FOR WEDNESDAY AND THURSDAY WITH TEMPERATURES MODERATING BY FRIDAY. UNSETTLED WEATHER IS LIKELY OVER THE WEEKEND.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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INTO THIS EVENING... BLUSTERY S-WINDS CONTINUE BUT WILL GRADUALLY DIMINISHING TOWARDS EVENING AS TEMPERATURES COOL AND BOUNDARY-LAYER MIXING LESSENS. WILL BE MONITORING THE BANDS LOW CLOUDS STREAMING NORTH AROUND THE HIGH AS SEEN PER VISIBLE SATELLITE. TONIGHT... INCREASING S WINDS AHEAD OF AN APPROACHING COLD FRONT. BLUSTERY AT THE SURFACE BUT BELOW WIND-ADV CRITERIA WITH 25 TO 30 MPH GUSTS AT MOST. WILL SEE THE DEVELOPMENT OF LOW CLOUDS/FOG/DRIZZLE AS MOISTURE CONVERGES ALONG THE NOSE OF A DEVELOPING LOW-LEVEL-JET POOLING BENEATH A DRY-AIR INVERSION ALOFT AND UNDERGOING WEAK ISENTROPIC ASCENT MAINLY ALONG THE S-COAST. BULK OF THE RAIN STAYS WEST ALONG WITH THE COLD FRONT. BUT SOME UNCERTAINTY AS TO WHETHER OUTCOMES THIS EVENING WILL BE DENSE FOG OR LOW CLOUDS. WITH HIGHER DEWPOINT AIR TRANSPOSED OVER COLDER OCEAN WATERS WOULD EXPECT DENSE FOG ALONG THE S-COAST...BUT WITH STRONG S WINDS...MECHANICAL MIXING MAY RESULT IN VERY LOW STRATUS. WILL HOLD OFF ON ANY ISSUANCE OF A DENSE FOG ADVISORY FOR NOW...BUT HIGHLIGHT THE THREAT IN THE HAZARDOUS WEATHER OUTLOOK.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
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TUESDAY... COLD FRONT SURGES INTO NEW ENGLAND. ANTICIPATING A DISTINCT BAND OF RAIN AHEAD OF THE FRONT WITH EMBEDDED HEAVIER SHOWERS AND ISOLATED THUNDERSTORMS. CONTINUED STRONG S LOW-LEVEL-JET AHEAD OF THE FRONT UP TO 80 MPH AT H925. THOUGH BOUNDARY-LAYER MIXING IS LIMITED BY WARMER AIR ALOFT... AM CONCERNED HEAVIER SHOWERS AND ISOLATED THUNDERSTORMS COULD LEND TO PRECIP-DRAG OF FASTER WINDS TO THE SURFACE. CONSIDERING FORECAST WEAK INSTABILITY AND SHEAR-VECTORS ROUGHLY PARALLEL TO THE FRONT... ANY THUNDERSTORM ACTIVITY COULD CONTAIN AN ISOLATED WIND THREAT. HAVE APPENDED THE CONVECTIVE THREAT OF GUSTY WINDS TO THE ISOLATED THUNDERSTORM POTENTIAL. TIGHTENING PRES-GRADIENT AND LIMITED BOUNDARY-LAYER MIXING SHOULD ALLOW FOR S WIND GUSTS UP TO 45 MPH POTENTIALLY EXCEEDING WIND ADV CRITERIA. MUCH LIKE TODAY...GUSTS EXCEEDING 45 MPH WILL BE ISOLATED. FEEL THE WIND ISSUES CAN BE HANDLED BY SHORT-FUSED PRODUCTS ESP WITH THE THREAT OF THUNDERSTORMS. WILL NOT ISSUE A WIND ADV WITH THIS FORECAST. S-FETCH WILL ADVECT PWATS OF AROUND 1.5-INCHES N ALONG WITH SURFACE DEWPOINTS IN EXCESS OF 50 DEGREES. TWO AREAS OF CONCERN: POTENTIAL URBAN/POOR DRAINAGE AND RIVER/SMALL-STREAM FLOODING ESP FOR THE CT-RIVER VALLEY...AS WELL AS THE POSSIBILITY OF DENSE FOG ALONG THE S-COAST WITH HIGHER DEWPOINT AIR OVER- RIDING A COLDER OCEAN. WILL HOIST A FLOOD WATCH FOR THE CT-VALLEY ACCORDINGLY. FURTHER HYDROLOGICAL DISCUSSION CAN BE FOUND LATER IN THE DISCUSSION DOWN BELOW. AS FOR THE DENSE FOG...WILL MONITOR OVERNIGHT AND UPDATE HEADLINES CLOSER TOWARDS MORNING AS FORECAST CONFIDENCE IS MODERATE AT THIS TIME. AS FOR COASTAL FLOODING THREATS...PLEASE SEE THE COASTAL FLOODING PORTION OF THE AFD OUTLINING THE POTENTIAL FOR MINOR SPLASHOVER ALONG THE S-COAST. TEMPERATURES WILL DROP IMMEDIATELY BEHIND THE SHARP COLD FRONT... MAINLY FOR THE EVENING PERIOD...SO WILL TABLE THE OUTCOMES BEHIND THE FRONT FOR THE TUESDAY NIGHT DISCUSSION. TUESDAY NIGHT... COLD FRONT PUSHES OFFSHORE SHORTLY AFTER MIDNIGHT. SHALLOW COLD AIR POURS IN VIA WESTERLY WINDS BENEATH SIGNIFICANTLY WARMER AIR ALOFT. WILL SEE THE BOUNDARY-LAYER DESTABILIZE UP TO H9 WITH COLD-AIR ADVECTION ALLOWING FOR THE MIX-DOWN OF FASTER MOMENTUM AND W-WIND GUSTS UP TO 45 MPH AT THE SURFACE. WIND ADVISORIES MAY NEED TO BE CONSIDERED...BUT AGAIN FEEL SUCH WINDS WILL BE BRIEF AND CAN BE HANDLED WITH SHORT-FUSED PRODUCTS. STRONG ASCENT PER RRQ AND MAIN SHORT-WAVE THROUGH THE NEGATIVELY TILTING TROUGH SHOULD RESULT IN PRECIP ON THE BACKSIDE OF THE FRONT WITHIN THE SHALLOW COLD AIR. BUT THIS SHOULD BE BRIEF WITH AN INFLUX OF DRIER AIR TO THE REAR /POSSIBLY ALSO THE DOWNSLOPING COMPONENT OFF THE BERKSHIRES WILL PRESENT LIMITATIONS/. WINTRY PRECIP TYPES WILL BE POSSIBLE FOR PORTIONS OF NW MA INTO S NH. ACCUMULATIONS IF ANY WILL BE JUST AROUND A TRACE. DO NOT BELIEVE WINTER WEATHER HEADLINES ARE NECESSARY. BIGGER CONCERN IS ON THE FLASH FREEZE POTENTIAL WITH THE IMMEDIATE INFLUX OF COLDER AIR. COULD SEE POTENTIAL BLACK-ICE IMPACTS FOR THE WEDNESDAY MORNING COMMUTE. LOWS FALLING AROUND THE UPPER-20S TO LOW-30S BY MORNING.
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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HIGHLIGHTS... * QUIET WEATHER BUT MUCH COOLER WED AND THU * TEMPERATURES START TO MODERATE FRI INTO THE WEEKEND * UNSETTLED WEATHER EXPECTED OVER THE WEEKEND 14/12Z MODELS ARE IN GOOD AGREEMENT ON THE OVERALL SYNOPTIC PATTERN THROUGHOUT THE LONG TERM. OVER THE WEEKEND...PARTICULARLY INTO EARLY NEXT WEEK...THERE START TO BE SOME TIMING DIFFERENCES BETWEEN THE GFS AND THE ECMWF. THESE WILL LIKELY HAVE SOME EFFECT ON THE TIMING OF THE SENSIBLE WEATHER...BUT THESE DIFFERENCES WILL BE RESOLVED OVER TIME. ACROSS THE BOARD...MOST OF THE MODELS AS WELL AS THE ENSEMBLES FOCUS ON THE SOUTHERN STREAM DEVELOPMENT OF LOW PRESSURE MOVING OUT OF THE GULF OF MEXICO...ACROSS THE CAROLINAS AND UP THE EASTERN SEABOARD OVER THE WEEKEND. EXPECT THIS IS THE LIKELIER SOLUTION GIVEN THE MODEL AGREEMENT...BUT THERE ARE A FEW ENSEMBLE MEMBERS/MODEL RUNS THAT ARE FOCUSING MORE ON THE NORTHERN STREAM LOW. SO THERE REMAINS UNCERTAINTY ON THE EXACT PATTERN FOR NEXT WEEKEND...AS THERE SHOULD AT THIS TIME RANGE. WEDNESDAY AND THURSDAY...THERE COULD BE A FEW LINGERING SHOWERS ALONG THE EAST COAST WEDNESDAY MORNING BUT THESE SHOULD COME TO AN END EARLY AS HIGH PRESSURE AND DRIER AIR BUILD IN BEHIND THE FRONT. THE WEATHER SHOULD BE QUIET ASIDE FROM THESE SHOWERS...BUT CHILLY WITH NORTHEASTERLY WINDS OFF THE OCEAN RESULTING IN TEMPERATURES WELL BELOW NORMAL FOR MID APRIL. FRIDAY...TEMPERATURES START TO MODERATE FOR MOST LOCATIONS. HOWEVER WITH NORTHEASTERLY SURFACE WINDS CONTINUING...EXPECT COASTAL LOCATIONS TO REMAIN CHILLY. SATURDAY THROUGH MONDAY...AS STATED ABOVE...THIS IS LIKELY TO BE A PERIOD OF UNSETTLED WEATHER AS A PAIR OF LOW PRESSURE SYSTEMS MOVE NORTHEASTWARD FROM THE CAROLINAS TO NEAR THE 40/70 BENCHMARK. THE FIRST IS FORECAST TO MOVE WELL OUTSIDE OF THE BENCHMARK...LIKELY BRINGING SHOWERS AND MORE WIDESPREAD PRECIPITATION TO THE EASTERN PART OF THE REGION SATURDAY. THE SECOND MOVES CLOSER TO THE BENCHMARK...WITH MORE WIDESPREAD PRECIPITATION EXPECTED THROUGHOUT THE REGION MONDAY. TEMPERATURES MODERATE ENOUGH THROUGH THIS PERIOD THAT THIS PRECIPITATION SHOULD FALL AS RAIN. THERE REMAINS UNCERTAINTY WITH THE TIMING OF THE LOW PRESSURE SYSTEMS...AND THUS THE RAINFALL THAT WILL NEED TO BE IRONED OUT OVER THE NEXT SEVERAL DAYS.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY/...MODERATE CONFIDENCE. 18Z UPDATE... STRONGEST WINDS ACROSS E/SE NEW ENGLAND SUSTAINED AROUND 25 KTS WITH GUSTS AROUND 35 KTS WITH ISOLATED GUSTS UP TO 40 KTS INTO THE EVENING. WINDS ANTICIPATED TO DROP OFF SLIGHTLY INCREASING LLWS THREATS AS WINDS 2 KFT AGL OVERNIGHT WILL BE AROUND 50 KTS. IN ADDITION TO LLWS...MAIN CONCERN FOR THE OVERNIGHT PERIOD IS THE DEVELOPMENT OF MVFR CIGS AROUND 1-2 KFT WITH THE LIKELIHOOD OF 1/2SM FG ALONG THE S-SHORELINE TERMINALS. WITH ANY DENSE FOG WILL LIKELY SOUP-OUT TO VV002. COLD FRONT SWEEPS ACROSS THE TERMINALS LATE TUESDAY INTO TUESDAY EVENING EXITING OFFSHORE SHORTLY AFTER MIDNIGHT WEDNESDAY. EXPECT A DISTINCT BAND OF RAIN WITH EMBEDDED HEAVIER SHOWERS AND POSSIBLE ISOLATED TSRA /BETTER CHANCES WILL BE ACROSS CT-RIVER VALLEY/. SUCH STRONGER ACTIVITY COULD YIELD AN ISOLATED WIND THREAT WITH S WIND GUSTS IN EXCESS OF 40 KTS. OTHERWISE ON AVERAGE 15 TO 25 KT SUSTAINED WINDS WITH 25 TO 35 KT GUSTS. EXPECT A MIX OF MVFR-IFR CIGS AND VSBYS. AFTER MIDNIGHT...WINDS BACK WEST AS TEMPS DROP CONSIDERABLY. WILL SEE W-WIND GUSTS UP TO 40 KTS AS CONDITIONS QUICKLY IMPROVE TO VFR. THERE IS THE POSSIBILITY OF SNOW/SLEET MIX TO THE REAR OF THE COLD FRONT...BUT BEST CHANCES OVER NW MA AND S NH. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. OUTLOOK...WEDNESDAY THROUGH SATURDAY... WEDNESDAY AND THURSDAY...LOW TO MODERATE CONFIDENCE. CONDITIONS SHOULD IMPROVE FROM WEST TO EAST ON WEDNESDAY TO VFR MOST LOCATIONS. TYPICALLY ON NE WINDS LOW CLOUDS DEVELOP ALONG THE EAST COAST OF MA INCLUDING KBOS. IFR CONDITIONS ALONG THE EAST COAST ARE THEN CLIMATOLOGICALLY LIKELY FOR BOTH DAYS. HOWEVER...MODELS ARE VERY DRY ON WEDNESDAY...SO THIS MAY NOT OCCUR. MOISTURE RETURNS THURSDAY THOUGH. FRIDAY...MODERATE TO HIGH CONFIDENCE. LOW CLOUDS/IFR CONDITIONS MAY LINGER ALONG THE EAST COAST WITH CONTINUED NE FLOW. OTHERWISE...VFR CONDITIONS EXPECTED. SATURDAY...LOW CONFIDENCE. MVFR/IFR CONDITIONS LIKELY PARTICULARLY EASTERN HALF OF THE AREA IN RAIN/FOG. && .MARINE...
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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 TUESDAY/...HIGH CONFIDENCE. GALE WARNINGS FOR STRONG S WINDS AHEAD OF AN APPROACHING COLD FRONT FOR TUESDAY THROUGH TUESDAY NIGHT...CONTINUING INTO EARLY WEDNESDAY MORNING AS WINDS BACK OUT OF THE WEST WITH PASSAGE OF THE COLD FRONT REMAINING IN EXCESS OF GALE-FORCE. WAVE HEIGHTS UP TO 10 FEET WILL BE POSSIBLE ON THE OUTER WATERS. ALSO WORTHY OF NOTE...AHEAD OF THE COLD FRONT EXPECT WIDESPREAD RAIN WITH EMBEDDED HEAVIER SHOWERS AND ISOLATED THUNDERSTORMS. AND ALSO BEGINNING TONIGHT...THERE IS ALSO A GREATER POTENTIAL FOR SEEING DENSE FOG ESP ALONG THE SOUTH COAST WITH VISIBILITIES DOWN TO A HALF-MILE OR LESS. OUTLOOK...WEDNESDAY THROUGH SATURDAY... WEDNESDAY...HIGH CONFIDENCE. NORTHWESTERLY GALES SLACKEN AS COLD FRONT MOVES EAST TOWARDS THE MARITIMES. WINDS SHIFT TO THE NORTH DURING THE AFTERNOON AND THEN THE NORTHEAST OVERNIGHT. SEAS DIMINISH SLOWLY AS HIGH PRESSURE BUILDS OVER NEW ENGLAND BUT WILL REMAIN ABOVE 5 FEET ON THE OUTER WATERS. THURSDAY AND FRIDAY...HIGH CONFIDENCE. NORTHEASTERLY WINDS AND SEAS REMAIN CLOSE TO OR ABOVE SMALL CRAFT CRITERIA THROUGH THE PERIOD. SEAS WILL BE HIGHEST ON THE OUTER WATERS. SATURDAY...LOW TO MODERATE CONFIDENCE. NORTHEASTERLY WINDS AND SEAS MAY INCREASE AS LOW PRESSURE PASSES WELL SOUTHEAST OF THE WATERS. MODERATE PROBABILITY OF SMALL CRAFT ADVISORIES BEING NEEDED. IN ADDITION...VISIBILITIES MAY BE LIMITED IN RAIN/FOG.
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&& .HYDROLOGY...
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A FLOOD WATCH HAS BEEN ISSUED FOR THE CONNECTICUT RIVER VALLEY. THIS IS DUE TO THE EXPECTATION THAT SWOLLEN RIVER CONDITIONS AS A RESULT OF UPSTREAM SNOWMELT COMBINING WITH THE BASIN AVERAGE 1.5 INCHES OF RAINFALL ANTICIPATED TUESDAY INTO TUESDAY NIGHT WILL RESULT IN MINOR FLOODING OF MAINSTEM RIVERS AND ADJOINING CREEKS AND STREAMS. THERE IS ALSO THE POTENTIAL FOR URBAN AND POOR DRAINAGE FLOODING THROUGHOUT THE WATCH AREA. FLOOD WARNINGS ARE ALREADY IN EFFECT ALONG THE CONNECTICUT RIVER FOR HARTFORD AND MIDDLE HADDAM. THOSE WITH INTERESTS ALONG LOWER REACHES OF CT RIVER SHOULD PAY ATTENTION TO THE LATEST FORECASTS AND CURRENT WATER LEVELS.
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&& .TIDES/COASTAL FLOODING...
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SOUTHERLY WINDS GUSTING 25 TO 35 MPH WILL PRODUCE A STORM-SURGE OF 1 TO 2 FEET ALONG THE SOUTH-COAST PRIOR TO THE COLD FRONTAL PASSAGE SHORTLY AFTER MIDNIGHT WEDNESDAY. COMBINED WITH TUESDAY EVENINGS HIGH TIDE...AND THERE IS THE POTENTIAL FOR SPLASHOVER AND MINOR COASTAL FLOODING OF LOW-LYING AREAS AND ROADWAYS ALONG THE SOUTH-COAST. THERE IS NOT ENOUGH CONFIDENCE AT THIS TIME TO WARRANT THE ISSUANCE OF A COASTAL FLOOD STATEMENT / ADVISORY FOR THE SOUTH- COAST. WILL EVALUATE WITH LATER FORECASTS AND HIGHLIGHT IN THE HAZARDOUS WEATHER OUTLOOK.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...FLOOD WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY MORNING FOR CTZ002-003. MA...FLOOD WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY MORNING FOR MAZ002>004-008>011-026. NH...FLOOD WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY MORNING FOR NHZ011-012-015. RI...NONE. MARINE...GALE WARNING FROM 2 PM TUESDAY TO 6 AM EDT WEDNESDAY FOR ANZ232-233-235-237-250-254>256. GALE WARNING UNTIL 6 AM EDT WEDNESDAY FOR ANZ230-231-234-236- 251.
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&& $$ SYNOPSIS...SIPPRELL NEAR TERM...SIPPRELL SHORT TERM...SIPPRELL LONG TERM...RLG AVIATION...RLG/SIPPRELL MARINE...RLG/SIPPRELL HYDROLOGY...SIPPRELL TIDES/COASTAL FLOODING...SIPPRELL

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