Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 221951 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 351 PM EDT WED APR 22 2015 .SYNOPSIS...
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A COLD FRONT IN THE HUDSON AND DELAWARE VALLEYS WILL MOVE NORTHEAST ACROSS SOUTHERN NEW ENGLAND THIS EVENING BRINGING SHOWERS AND ISOLATED THUNDER. COOLER WEATHER FOLLOWS THROUGH THE WEEKEND WITH SPOTTY SHOWERS OR SPRINKLES. COOLER WEATHER LOOKS TO CONTINUE INTO NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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* HIGH CONFIDENCE IN SCATTERED TO NUMEROUS SHOWERS THIS EVENING * LOW CONFIDENCE FOR THUNDERSTORMS WITH SMALL HAIL AND GUSTY WINDS THIS EVENING CLOUD SHIELD ACROSS NORTHERN/WESTERN NEW ENGLAND WILL SPREAD EAST BY SUNSET. LOW PRESSURE OVER SOUTHERN NEW YORK IS MOVING NORTHEAST AND WILL PULL A COLD FRONT FROM EASTERN PA ACROSS SOUTHWESTERN NEW ENGLAND BY EVENING AND ACROSS THE REMAINDER OF SOUTHERN NEW ENGLAND BY 2 AM. SPC MESOANALYSIS SHOWS CAPE UP TO 250 J/KG OVER THE SUNNIER PORTIONS OF SOUTHERN NEW ENGLAND. HIGHER VALUES ARE FOUND OVER ALONG THE MID ATLANTIC COAST. LI VALUES NEAR ZERO SOUTHERN NY THROUGH VIRGINIA WHILE 0 TO +2 OVER SOUTHERN NEW ENGLAND. MID LEVEL LAPSE RATES 7 TO 7.5C FROM NEW ENGLAND TO VIRGINIA. LEFT EXIT REGION OF UPPER JET...DIVERGENCE ZONE...IS FOCUSSED ALONG THE MID ATLANTIC COAST ALTHOUGH IS COULD ADVECT EAST AND CLIP THE SOUTH COAST OF NEW ENGLAND. MOST SUPPORT FOR SIGNIFICANT CONVECTION IS LOCATED TO OUR SOUTHWEST AND SHOULD REMAIN SOUTH OF SOUTHERN NEW ENGLAND. SHOWERS ASSOCIATED WITH THE FRONT SHOULD HOLD TOGETHER THROUGH THE EVENING AND EARLY NIGHT MARCHIG SOUTHWEST TO NORTHEAST ACROSS OUR AREA AND BRINGING A PERIOD OF SHOWERS TO ALL AREAS. INSTABILITY COULD POP A BRIEF TSTM ALONG THE LINE OF SHOWERS. ALSO...FREEZING LEVEL BELOW 5000 FEET AND WET BULB ZERO NEAR 3100 FEET SUGGEST AT LEAST A SMALL POTENTIAL FOR SOME SMALL HAIL. AS THE SHOWERS MOVE ACROSS DURING THE EARLY NIGHT THEY WILL LOSE THEIR SUPPORT FROM THE SUN AND THEY WILL START TO INGEST COLD MARINE AIR EAST OF WORCESTER-NEW LONDON. EXPECT SHOWERS TO WEAKEN OVER SOUTHEASTERN NEW ENGLAND TONIGHT. THE STRONG GUSTY WINDS WHICH DEVELOPED DUE TO SOLAR HEATING SHOULD ALSO DIMINISH AFTER SUNSET. ONCE THE COLD FRONT MOVES TO OUR EAST...EXPECT SHOWERS TO END IN MOST AREAS. APPROACHING COLD POOL ALOFT MAY DESTABILIZE NORTHWESTERN MASS OVERNIGHT AND CAUSE SCATTERED RAIN OR SNOW SHOWERS IN THAT AREA. WE STAYED CLOSE TO MODEL GUIDENCE FOR MIN TEMPS...ROUGHLY 35 NORTHWEST TO 45 SOUTHEAST.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
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CUT-OFF UPPER LOW SPINS OVER NEW ENGLAND DURING THIS PERIOD. THIS WILL HOLD THE COLD POOL ALOFT OVER THE REGION. DAYTIME HEATING MAY DESTABILIZE THE AIRMASS AND GENERATE A FEW WIDELY SCATTERED RAIN SHOWERS. MIXING MAY REACH AS HIGH AS 800 MB...WHERE TEMPERATURES OF -8C TO -10C WOULD SUPPORT MAX SFC TEMPS IN THE UPPER 40S AND LOWER 50S. WINDS IN THIS MIXED LAYER ARE FORECAST AT 20-25 KNOTS...GUSTS WITHIN THIS RANGE ARE EXPECTED DURING THE LATE MORNING AND AFTERNOON. THE COLD AIRMASS STAYS IN PLACE THURSDAY NIGHT. SUFFICIENT MOISTURE IN THE COLUMN TO SUGGEST AT LEAST SOME SKY COVER OVERNIGHT AND SUFFICIENT PRESSURE GRADIENT TO MAINTAIN SOME WIND. WHILE RADIATIONAL COOLING IS QUESTIONABLE...ADVECTION COOLING IS STILL IN PLAY. MIN TEMPS UNDER THE COLD POOL CLOUDS LAST NIGHT WERE AT OR BELOW FREEZING. EXPECT WE WILL BE CLOSE TO THAT THURSDAY NIGHT WITH MINS IN THE UPPER 20S AND 30S. IF SKIES DID CLEAR AND WE WERE TO RADIATE...SFC TEMPS WOULD FALL TO THE MID 20S OVER A WIDE PORTION OF THE INTERIOR.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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HIGHLIGHTS... * UNSEASONABLY COOL FRI-SUN WITH A SPOT SHOWER OR TWO AT TIMES * UNCERTAINTY IN UPPER LEVEL PATTERN NEXT WEEK OVERVIEW... OVERALL THE 00Z GUIDANCE IS IN GOOD AGREEMENT WITHIN THE MEDIUM AND LONG RANGE. UPPER LEVEL LOW PREVAILS ACROSS SOUTHEAST CANADA AND SUPPORTS BELOW NORMAL TEMPERATURES AND INSTABILITY SHOWERS FOR MOST OF THE PERIOD. THIS LOW MAY SHIFT NORTHEASTWARD FOR THE EXTENDED...DAYS 6-7...INTO THE CANADIAN MARITIMES AND NORTHERN NEW ENGLAND. THIS IS SUPPORTED BY THE GEFS...EC ENSEMBLES AND GFS. STILL A LOT OF UNCERTAINTY ON WHEN THE UPPER LEVEL LOW WILL KICK OUT BUT AM LEANING TOWARDS THE MON/TUES TIMEFRAME PRIOR TO ANOTHER LOW DEVELOPING IN ITS WAKE. DETAILS... * FRIDAY INTO MONDAY...MODERATE CONFIDENCE. STRONG CUTOFF LOW WILL CONTINUE TO SPIN OVER THE NORTHEAST DURING THIS TIME PERIOD. TELECONNECTION INDICES OF -NAO/-AO AND +PNA CONTINUE TO SUPPORT THIS STAGNANT PATTERN OVER NEW ENGLAND. SEVERAL PACIFIC WAVES TRY TO PUSH THROUGH THE FLOW...BUT APPEAR TO EITHER GET SHEARED TO THE SOUTH OR GET CAUGHT UP WITHIN THE UPPER LEVEL FLOW. REGARDLESS...SOUTHERN NEW ENGLAND REMAINS IN A NORTHWEST TO WEST FLOW THROUGH MUCH OF THE PERIOD WITH A FEW UPPER LEVEL DISTURBANCES SPINNING AROUND THE SYSTEM. THIS LOW AND ITS ASSOCIATED COLD POOL WILL CONTINUE TO KEEP TEMPS BELOW AVERAGE FOR MUCH OF THE FORECAST. A FEW SITES MAY WARM INTO THE 60S AS THE LOW BEGINS TO PUSH NORTHEASTWARD NEXT WEEK...BUT OVERALL TREND IS 5-10 F DEGREES BELOW NORMAL. ANTICIPATE CLEARING SKIES OVERNIGHT WITH DIURNAL CU DURING THE DAY. DEPENDING ON HOW POTENT THE COLD POOL IS OR IF A SHORTWAVE MOVES THROUGH MAY SEE ISOLATED TO SCT SHOWERS DURING THE AFTERNOON HOURS. AREAS THAT HAVE THE BEST CHANCE FOR ANY PRECIP WILL BE NORTH OF THE PIKE...CLOSER TO THE LOW PRESSURE. * TUESDAY AND BEYOND...LOW CONFIDENCE. GUIDANCE BEGINS TO SPLIT DURING THIS PORTION OF THE FORECAST. HOWEVER WITH THE CONTINUE SHARP NEGATIVE NAO AND AO PLUS THE TRENDING POSITIVE PNA...EXPECT A CONTINUATION OF BELOW AVERAGE TEMPS AND HIT OR MISS SHOWERS INTO NEXT WORK WEEK. THE GFS IS MORE AMPLIFIED WITH NORTHERN SHORTWAVE CUTTING OFF ACROSS THE PLAINS ON WED WHILE THE EC APPEARS TO BE SLOWER ON CUTTING OF A LOW OVER THE GREAT LAKES BY THURSDAY. REGARDLESS APPEARS THAT THIS UPPER LEVEL LOW WILL IMPACT SOUTHERN NEW ENGLAND WEATHER WELL INTO NEXT WEEK.
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&& .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 /THROUGH THURSDAY NIGHT/... THIS AFTERNOON AND TONIGHT...GENERALLY HIGH CONFIDENCE. VFR CONDITIONS WILL BE PREDOMINANT. A COLD FRONT MOVING ACROSS FROM NEW YORK WILL BRING A BAND OF SHOWERS THROUGH THE REGION LATE AFTERNOON AND EARLY TONIGHT. VSBYS SHOULD LOWER TO MVFR IN ANY SHOWERS. CIGS COULD ALSO BRIEFLY LOWER TO MVFR...BUT THE BETTER CONFIDENCE IS THAT THESE WILL REMAIN VFR. SOUTH/SOUTHWEST WINDS WILL GUST 25 TO 30 KNOTS THROUGH EVENING THEN DIMINISH. WINDS WILL SHIFT WEST AFTER THE COLD FRONT MOVES THROUGH AND OVERNIGHT. LOW CONFIDENCE ON FORMATION OF ISOLATED TSTMS. SOME SUPPORTING CONDITIONS ARE THERE...OTHERS ARE NOT. BEST CHANCE WILL BE NEW YORK CITY AND SOUTHWEST...SO THE HIGHEST VALUE OF OUR LOW CONFIDENCE WOULD BE IN CONNECTICUT. CONDITIONS MAY BRIEFLY SUPPORT SMALL HAIL IN ANY SHOWERS OR ISOLATED TSTMS. THURSDAY...HIGH CONFIDENCE IN VFR CONDITIONS. BRIEF...SPOTTY DIURNAL SHOWERS POSSIBLE...MAINLY IN NORTHERN/WESTERN MASS. THURSDAY NIGHT...HIGH CONFIDENCE. VFR. KBOS TAF...HIGH CONFIDENCE IN OVERALL TAF. MODERATE CONFIDENCE IN TIMING OF SHOWERS. KBDL TAF...HIGH CONFIDENCE IN OVERALL TAF. MODERATE CONFIDENCE IN TIMING OF SHOWERS. OUTLOOK...FRIDAY THROUGH SUNDAY... FRIDAY-SAT...HIGH CONFIDENCE. MAINLY VFR. CONDITIONS COULD LOWER TO MVFR QUICKLY IN A BRIEF DIURNALLY DRIVEN SHOWER OR TWO. SUNDAY...MODERATE CONFIDENCE. VFR. && .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 /TONIGHT THROUGH THURSDAY NIGHT/... TONIGHT AND THURSDAY...HIGH CONFIDENCE. SOUTHEAST SWELL CONTINUES TO INFLUENCE OUR WATERS...MAINTAINING 5 TO 7 FOOT SEAS ESPECIALLY ON OUR EXPOSED SOUTHERN WATERS. WINDS TODAY WERE GUSTING 25-30 KNOTS NEARSHORE BUT LESS FARTHER OFFSHORE. WINDS WILL DIMINISH NEARSHORE THIS EVENING BUT SEAS SHOULD LINGER ON THE EXPOSED WATERS. WEST WINDS THEN PICK UP AGAIN ON THURSDAY WITH GUSTS NEAR 25 KNOTS. RATHER THAN GO OFF- AGAIN/ON-AGAIN WITH THE SMALL CRAFT HEADLINES...WE WILL MAINTAIN THEM FOR MOST WATERS THROUGH THURSDAY. EXCEPTION WILL BE BOSTON HARBOR AND NARRAGANSETT BAY FOR WHICH THE HEADLINES ARE MORE DIRECTLY TIED TO THE DIURNAL WINDS. THE OTHER CONCERN WILL BE FOR A BAND OF SHOWERS EARLY TONIGHT. IF ENOUGH INSTABILITY CAN BE REALIZED...A FEW OF THE HEAVIER SHOWERS MAY CONTAIN GUSTY WINDS/SMALL HAIL. LOW RISK OF A FEW THUNDERSTORMS AS WELL. THURSDAY NIGHT...HIGH CONFIDENCE. WEST WINDS DIMINISH A LITTLE BUT REMAIN GUSTING NEAR 20 KNOTS ON THE SOUTHERN WATERS. SEAS/SWELL SUBSIDE A LITTLE BUT MAINTAIN 5-6 FEET ON THE SOUTHERN AND SOUTHEAST OUTER WATERS. OUTLOOK...FRIDAY THROUGH SUNDAY... FRIDAY...HIGH CONFIDENCE. MODEST WESTERLY FLOW AS A RESULT OF CLOSED LOW PRESSURE ACROSS QUEBEC. ENOUGH COLD ADVECTION OVER THE WATERS WILL BE PRESENT TO GENERATE PERIODS OF 25 KNOT WIND GUSTS. MARGINAL SMALL CRAFT ADVISORY SEAS EXPECTED ACROSS THE OUTER- WATERS AT TIMES...BUT WITH GOOD VISIBILITY. SATURDAY INTO SUNDAY...HIGH CONFIDENCE. UPPER LEVEL LOW WILL CONTINUE TO SPIN ACROSS THE NORTHEAST. EXPECT BOTH WIND AND SEAS TO REMAINS BELOW SMALL CRAFT ADVISORY.
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&& .HYDROLOGY...
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A COMBINATION OF RAINFALL AND SNOWMELT ACROSS NORTHERN NEW ENGLAND WAS MAKING ITS WAY DOWN THE CONNECTICUT RIVER. THIS COMBINED WITH TIDAL INFLUENCES AT THE MOUTH OF THE RIVER WILL RESULT IN MINOR FLOODING ACROSS PORTIONS OF THE LOWER CONNECTICUT RIVER. THE RIVER NEAR HARTFORD IS NOT EXPECTED TO APPROACH ITS FLOOD STAGE UNTIL THURSDAY EVENING. NEAR MIDDLE HADDAM...THE TIDAL INFLUENCE WILL BE STRONGER. MINOR FLOODING IS ONGOING DURING AT LEAST APART OF EACH TIDE CYCLE. THIS IS EXPECTED IS EXPECTED TO CONTINUE THROUGH AT LEAST SATURDAY MORNING.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ231>234. SMALL CRAFT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR ANZ230- 236. SMALL CRAFT ADVISORY UNTIL 6 PM EDT THURSDAY FOR ANZ235-237- 250-254>256. SMALL CRAFT ADVISORY UNTIL 3 AM EDT THURSDAY FOR ANZ251. && $$ SYNOPSIS...WTB/DUNTEN NEAR TERM...WTB SHORT TERM...WTB LONG TERM...DUNTEN AVIATION...WTB/DUNTEN MARINE...WTB/DUNTEN HYDROLOGY...

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