Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 222001 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 401 PM EDT TUE JUL 22 2014 .SYNOPSIS... WARM AND HUMID WEATHER IS EXPECTED THROUGH WEDNESDAY NIGHT AHEAD OF AN APPROACHING COLD FRONT. THE FRONT WILL TRIGGER SCATTERED SHOWERS AND THUNDERSTORMS WEDNESDAY AFTERNOON AND EVENING. A FEW STRONG STORMS ARE POSSIBLE ESPECIALLY INLAND. SHOWERS MAY LINGER INTO THURSDAY ALONG THE SOUTH COAST HOWEVER THE TREND WILL BE FOR DRIER AND LESS HUMID WEATHER THURSDAY NIGHT INTO SATURDAY. THE WEATHER PATTERN THEN BECOMES UNSETTLED AND MORE HUMID BEGINNING SUNDAY AND ESPECIALLY EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 400PM UPDATE... OVERALL TRENDS IN THE FORECAST REMAIN ON TRACK FOR THE AFTERNOON HOUR. HIGH PRESSURE CONTINUES TO SLIDE EASTWARD ALLOWING FOR RETURN FLOW INTO THE REGION. THIS HAS BEEN INCREASING DEWPOINTS AND THUS THE MUGGINESS FACTOR ACROSS SOUTHERN NEW ENGLAND. ISOLATED SHOWERS HAVE POPPED UP ACROSS UPSTATE NY AND VT BUT QUICKLY DIE OUT. A FEW OF THESE SHOWERS MAY MAKE THERE WAY INTO SOUTHERN NEW ENGLAND BUT THEY WILL STRUGGLE DUE TO MID-LEVEL CAP AND LACK OF ANY LIFT. TONIGHT... HIGH PRESSURE CONTINUES TO REMAIN WELL EAST OF THE AREA TONIGHT WITH UPPER LEVEL FLOW BECOMING MORE ZONAL. SOUTHERLY FLOW WILL CONTINUE ACROSS THE REGION INCREASING THE MOISTURE LEVELS ALLOWING FOR A VERY MUGGY NIGHT...AS TEMPS DROP ONLY TO THE MID TO UPPER 60S. BECAUSE OF THE INCREASE IN MOISTURE ANTICIPATE PATCHY VALLEY FOG TO DEVELOP LIMITING VSBYS. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... TOMORROW AND TOMORROW NIGHT... * A FEW STRONG TO SEVERE STORMS POSSIBLE LATE WEDNESDAY AFTERNOON INTO THE EVENING HOURS * THE WEATHER WILL BECOME MORE INTERESTING BEGINNING TOMORROW AFTERNOON INTO THE OVERNIGHT HOURS AS A COLD FRONT BEGINS TO APPROACH THE REGION. AHEAD OF THE APPROACHING COLD FRONT EXPECT A FAIRLY QUIET MORNING WITH PARTLY SUNNY SKIES TO START. THERE IS A GOOD AMOUNT OF MIXING ACROSS THE REGION ALLOWING SOUTHWESTERLY WINDS TO GUST BETWEEN 20-30 MPH. THIS WILL ALSO ALLOW FOR TEMPS TO WARM AT OR ABOVE 90...ESPECIALLY SINCE SEVERAL SITES REACHED 90F TODAY. COLD FRONT WILL BEGIN TO APPROACH THE REGION BY LATE AFTERNOON. BUFKIT SOUNDINGS DO INDICATE A CAP ACROSS THE REGION BUT WITH FALLING HEIGHTS AND COOLING TEMPS ALOFT...BELIEVE THE CAP WILL BREAK. STILL SOME UNCERTAINTY ON THE EXACTING TIMING BUT FEEL IT WILL BE CLOSER TO THE LATE AFTERNOON HOURS. BECAUSE OF THE MOIST UNSTABLE AIRMASS ACROSS SOUTHERN NEW ENGLAND...ONCE THE FRONT APPROACHES STORMS WILL DEVELOP...WITH THE COVERAGE BEING MORE SCATTERED TO START WITH PERHAPS TURNING INTO A BROKEN LINE. THE REGION WILL BE VERY UNSTABLE WITH MUCAPE VALUES WILL BE BETWEEN 1500- 2500 J/KG WITH SHEAR VALUES VERY MEAGER...15 KTS FROM 0-6KM. THE ONLY DOWNFALL FOR ANY AFTERNOON CONVECTION IS THE LACK OF DEEP LAYER MOISTURE. HOWEVER CLOSER TO 00Z AND INTO 06Z THE BETTER MOISTURE APPROACHES THE REGION AND WITH LINGERING INSTABILITY AND BETTER JET DYNAMICS ANTICIPATE THUNDERSTORMS TO CONTINUE INTO THE OVERNIGHT HOURS. THE BEST AREA TO SEE THE STRONG TO SEVERE STORMS WILL BE NORTH AND WEST OF I-95. THE BIGGEST THREATS FOR THESE STORMS WILL BE STRONG DAMAGING WINDS AND LOCALIZED FLASH FLOODING. HELD OFF ON FLASH FLOOD WATCH AS PWAT ANOMALIES ARE ONLY 1 STANDARD DEVIATION AWAY. THEREFORE FEEL THAT FLOODING POTENTIAL WILL BE LOCALIZED WITHIN THE STRONGER CONVECTION. SHEAR VALUES ARE FAIRLY WEAK ACROSS THE REGION...HOWEVER ACROSS THE IMMEDIATE NW ZONES...THERE IS MARGINAL SHEAR VALUES CLOSER TO 30 KTS AND WITH SOME TURNING IN THE HODOGRAPHS COLD SEE UPDRAFTS SUSTAIN THEMSELVES TO PRODUCE DAMAGING WINDS. AT THIS TIME CONTINUED WITH ENHANCE WORDING OF GUSTY WINDS AND HEAVY RAINFALL. FRONT WILL MOVE NORTHWEST DOWN TO THE SOUTHEAST THROUGH THE OVERNIGHT HOURS. AS MENTIONED BEFORE BELIEVE CONDITIONS WILL STILL BE FAVORABLE FOR THUNDERSTORMS TO CONTINUE THROUGH THE OVERNIGHT. HOWEVER BELIEVE THE STRONG TO SEVERE THUNDERSTORM THREAT WILL DIMINISH AND TURN MORE TO A HEAVY RAIN THREAT AFTER 06Z. && .LONG TERM /THURSDAY THROUGH TUESDAY/... HIGHLIGHTS... * MUCH COOLER THU ALONG WITH RAIN LINGERING SOUTH COAST * DRY...LESS HUMID AND SEASONABLE THU NGT THRU SAT * PATTERN BECOMES UNSETTLED AND MORE HUMID SUN INTO NEXT WEEK SYNOPTIC OVERVIEW AND MODEL PREFERENCES.... NORTHERN STREAM MID LEVEL TROUGH MOVES ACROSS THE AREA THU WITH ITS SURFACE COLD FRONT SLOWLY EXITING THE SOUTH COAST. POST FRONTAL AIRMASS OVERSPREADS THE REGION FRI. THE MID LEVEL MEAN TROUGH AXIS THEN MOVES OFFSHORE SAT WITH SUBTLE HEIGHT RISES AND ANTICYCLONIC FLOW OVERSPREADING NEW ENGLAND. THIS WILL MAINTAIN DRY WEATHER OVER THE AREA THRU SAT. BY SUNDAY AND ESPECIALLY EARLY NEXT WEEK ALL MODEL GUIDANCE INCLUDING THE GEFS AND ECENS ENSEMBLES ARE IN GOOD AGREEMENT ON A HIGH AMPLITUDE /+2 SD/ LONG WAVE TROUGH SETTING UP OVER SOUTHEAST CANADA SOUTHWARD INTO THE OH VLLY. BOTH DETERMINISTIC AND ENSEMBLE GUIDANCE ARE IN VERY GOOD AGREEMENT ON THE LARGE SCALE FLOW ACROSS NORTH AMERICA THIS PERIOD. THEREFORE WILL BASE THIS PORTION OF THE FORECAST ON A MODEL BLEND. DAILY DETAILS... THURSDAY... MID LEVEL TROUGH AXIS STILL WELL WEST OF NEW ENGLAND AT 12Z THU. THUS COLD FRONT WILL BE SLOW TO EXIT THE SOUTH COAST WHICH WILL INCREASE THE RISK FOR SHOWERS AND POSSIBLE A TSTM TO LINGER ACROSS THIS REGION. THE HIGH RES DETERMINISTIC GUID /GFS AND NAM/ ARE SLOWER WITH THE FROPA AS THESE MODELS FORM A STRONGER FRONTAL WAVE THAN THE ENSEMBLES. THIS IS POSSIBLE GIVEN THE HIER RES MODELS WOULD PERFORM BETTER THAN THE COURSE ENSEMBLES SIMULATING A SMALL SCALE FRONTAL WAVE. THEREFORE WILL GO WITH LIKELY POPS THU MORNING ACROSS RI AND SOUTHEAST MA AND TRENDING TO CHANCE AS THE RAIN SHIELD MOVES SLOWLY SOUTHEAST AND EVENTUALLY OFFSHORE LATER THU. DEPARTURE OF RAIN WILL BE CRITICAL TO TEMP FORECAST AS THE WETTER GFS 2 METER TEMPS NEVER CLIMB OUT OF THE 60S! EVEN THE WARMER ECMWF AND NAM 2 METER TEMPS ARE ONLY INTO THE L70S. THUS A COOLER DAY ON TAP THU AND IF THE GFS VERIFIES OUR TEMPS WILL BE TOO WARM. ELSEWHERE ACROSS INTERIOR CT/MA INTO SOUTHWEST NH MAINLY DRY CONDITIONS SHOULD PREVAIL WITH LOTS OF MID AND HIGH CLOUDS ALONG WITH N-NE WINDS YIELDING A COOLER DAY. THURSDAY NIGHT THRU SATURDAY... POST FRONTAL AIRMASS OVERSPREADS THE AREA THU NIGHT AND FRI WITH A 850 TEMP ANOMALIES AROUND 1 STANDARD DEVIATION COOLER THAN CLIMO... ABOUT +10C/+11C. HENCE REFRESHING AIRMASS WITH DEW PTS IN THE 50S. THE CORE OF THE DRY/COOLER AIRMASS WILL BE OVER SOUTHERN NEW ENGLAND AROUND 12Z FRI. THIS WILL YIELD A VERY COMFORTABLE AND COOL TEMPS THU NIGHT/EARLY FRI AM. SUNDAY THRU TUESDAY... PATTERN BECOMES UNSETTLED AS LONG WAVE TROUGH SETS UP OVER SOUTHEAST CANADA SOUTHWARD INTO THE OH VALLEY. THIS PROVIDES DEEP CYCLONIC FLOW ACROSS THE NORTHEAST ALONG WITH A BROAD SURFACE LOW PRES OVER NY AND NEW ENGLAND. LOW LEVEL FLOW WILL BE SSW OFF THE ATLANTIC INTO NEW ENGLAND SO EXPECT INCREASING HUMIDITY ALONG WITH THE RISK OF SCATTERED SHOWERS AND THUNDERSTORMS. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH WEDNESDAY NIGHT/... GENERALLY MODERATE CONFIDENCE ON FORECAST. BEFORE 00Z...VFR ACROSS THE REGION. WEAK/SHALLOW SEA BREEZE ON EAST COASTLINE. TONIGHT INTO WED...VFR TO START. ANTICIPATE PATCHY MVFR FOG/CIGS ACROSS INTERIOR DUE TO INCREASE OF LOW LEVEL MOISTURE. STRATUS AND FOG AGAIN OVER THE CAPE AND ISLANDS DROPPING TO MVFR/IFR. CONDITIONS CLEARING TO VFR BY DAY BREAK. LATE WED AFTERNOON INTO THURSDAY...MVFR CIGS AND VSBYS IN VICINITY OF SCT TSTMS AHEAD OF A COLD FRONT. A FEW TSTMS MAY BRIEFLY LOWER CIGS/VSBYS TO IFR LEVELS. ALSO...A FEW TSTMS MAY PRODUCE STRONG WIND GUSTS. VSBYS MAY BE REDUCE IN PATCHY FOG AHEAD OF FRONTAL PASSAGE AS WELL. KBOS TAF...HIGH CONFIDENCE. MODERATE CONFIDENCE IN SEABREEZE TIMING. T-STORMS POSSIBLE BY WED LATE AFTERNOON. KBDL TAF...HIGH CONFIDENCE IN TAF. LOW PROB ON FOG POTENTIAL TONIGHT. T-STORMS POSSIBLE BY WED AFTERNOON. OUTLOOK...THURSDAY THROUGH SUNDAY...MODERATE CONFIDENCE MVFR POSSIBLE BOSTON TO PROVIDENCE IN RAIN...POSSIBLY IFR SOUTH COAST WITH VFR NORTHWEST MA INTO SOUTHWEST NH. THEN VFR ALL TERMINALS THU NIGHT INTO SAT. LOW RISK OF MVFR IN SCATTERED SHOWERS/TSTMS SUN AFTN WESTERN NEW ENGLAND. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH WEDNESDAY/...MODERATE CONFIDENCE. WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY LEVELS THROUGH TONIGHT. THE SW FLOW WILL STRENGTHEN AHEAD OF A COLD FRONT ON WED WITH A RISK OF GUSTS APPROACHING 25 KT. AREAS OF FOG WILL GRADUALLY BURN OFF THIS MORNING BUT MAY REDEVELOP ALONG THE SOUTH COASTAL WATERS TONIGHT. OUTLOOK...THURSDAY THROUGH SUNDAY...MODERATE CONFIDENCE. THU...MODEST N-NE WIND ALONG WITH PERIODS OF RAIN ESPECIALLY SOUTH COASTAL WATERS. FRI/SAT...PLEASANT BOATING WEATHER WITH DRY CONDITIONS AND LIGHT WINDS BECOMING A MODEST SSW SAT AFTN. SUN...MODEST SSW WIND ALONG WITH LOW RISK OF A FEW SHOWERS NEAR SHORE. OTHERWISE MAINLY GOOD VSBYS. && .EQUIPMENT... KBOX RADAR MAY BE IN STANDBY MODE TOMORROW MORNING WHILE CONSTRUCTION TAKES PLACE NEARBY. THE RADAR WILL RETURN TO SERVICE BY THE AFTERNOON HOURS IN ANTICIPATING OF UPCOMING CONVECTION. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 10 AM TO 7 PM EDT WEDNESDAY FOR ANZ230>237-251. SMALL CRAFT ADVISORY FROM 2 AM WEDNESDAY TO 3 AM EDT THURSDAY FOR ANZ250-254. && $$ SYNOPSIS...NOCERA/DUNTEN NEAR TERM...DUNTEN SHORT TERM...DUNTEN LONG TERM...NOCERA AVIATION...NOCERA/DUNTEN MARINE...NOCERA/DUNTEN EQUIPMENT...STAFF

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