Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 222331 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 731 PM EDT FRI MAY 22 2015 .SYNOPSIS... A COLD FRONT WILL MOVE OFFSHORE THIS EVENING...USHERING IN UNSEASONABLE COLD AIR INTO MUCH OF WESTERN MA. SOME LOCATIONS SHOULD SEE NEAR RECORD LOW MINIMUM TEMPERATURES. THERE WILL ALSO BE AREAS OF FROST TONIGHT. GRADUAL WARMING IS EXPECTED THROUGH NEXT WEEK...LEADING TO HOT AND HUMID CONDITIONS BY MID WEEK. THERE IS THE LOW CHANCE FOR A SHOWER OR THUNDERSHOWER MONDAY THROUGH WEDNESDAY. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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7PM UPDATE... COLD FRONT /ALTHOUGH CURRENTLY ACTING MORE LIKE A DRY-LINE/ IS NOW DRAPED ACROSS ERN MA AND RI...JUST E OF A PVD-BOS LINE. THERE HAS BEEN SOME ATTEMPT AT -SHRA ACTIVITY...BUT WITH A VERY DRY AIRMASS AND DWPTS DROPPING INTO THE LOW 20S BEHIND IT...THEY HAVE BEEN STRUGGLEING AT BEST. FEEL CONFIDENT ENOUGH FOR NIL POPS THE REST OF THE OVERNIGHT. OTHERWISE...THIS TEMP DECLINE AND A LOOK AT LATEST MESO-SCALE GUIDANCE STILL SHOWS DECOUPLING IN THE AREAS CURRENTLY HIGHLIGHTED BY FROST/FREEZE HEADLINES SO NO PROPOSED CHANGES. WOULD LIKE TO HIGHLIGHT THE I-495 CORRIDOR HERE THOUGH...AS AN AREA WHERE SOME LOW-LYING LCOATIONS MAY EXPERIENCE NEAR FREEZING TEMPERATURES AND SOME VERY PATCHY FROST BY MORNING. THESE ARE TYPICAL OUTLIERS. PREVIOUS DISCUSSION... OTHER THAN A SPOT EVENING SHOWER ASSOCIATED WITH THE FRONTAL PASSAGE...DRY WEATHER PREVAILS OVERNIGHT. STRONG COLD AIR ADVECTION BEHIND DEPARTING THIS FRONT...WILL RESULT IN STRONG NEGATIVE SEASONAL DEPARTURES...AND NEAR RECORD LOW TEMPERATURES FOR SOME LOCATIONS. THE BIG QUESTION IS WHETHER OR NOT WINDS WILL DECOUPLE SUFFICIENTLY TO ALLOW FOR FROST FORMATION. THE RAW MODEL GUIDANCE SAYS NO...BUT THE MOS OUTPUT SUGGESTS YES. SINCE THE MAJORITY OF RAW MODEL GUIDANCE HAS A GENERAL HIGH BIAS FOR WIND SPEED...WILL GO MORE WITH THE SCENARIO OF DECOUPLING WINDS AND STRONGER RADIATIONAL COOLING. FAVORED A CONSENSUS OF THE MOS GUIDANCE... WHICH HAD LOWER TEMPERATURES THAN THE MAJORITY OF MODEL 2 METER TEMPERATURES. FREEZE WARNINGS ISSUED FOR NORTHWEST MA...SURROUNDED BY A RING OF FROST ADVISORIES. WE COULD SEE SOME FROST IN THE NORMALLY COLDER LOCATIONS ACROSS EASTERN MA...SUCH AS NORWOOD AND TAUNTON...BUT FEEL IT WILL NOT BE WIDESPREAD ENOUGH TO WARRANT AN ADVISORY.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... HIGHER PRESSURE OVER THE MID ATLANTIC STATES GRADUALLY INCREASES ITS INFLUENCE ON OUR WEATHER SATURDAY INTO SATURDAY NIGHT. WITH THIS HIGH PRESSURE REMAINING TO OUR SOUTH...WE WILL SEE A CONTINUATION OF A GENERALLY WEST WIND. PRESENT THINKING IS THIS FLOW WILL BE STRONG ENOUGH TO PREVENT SEABREEZES FROM DEVELOPING. UNSEASONABLE COLD CONTINUES...WITH HIGH TEMPERATURES SATURDAY ONLY RECOVERING INTO THE LOWER TO MID 60S AT MOST. MORE SEASONABLE TEMPERATURES ARE EXPECTED FOR SATURDAY NIGHT LOW TEMPERATURES. DRY WEATHER CONTINUES. && .LONG TERM /SUNDAY THROUGH FRIDAY/... HIGHLIGHTS... - SOME SHOWERS POSSIBLE OVER THE INTERIOR MONDAY...BUT HIT-OR-MISS - GRADUAL WARMING LEADS TO HOT AND HUMID CONDITIONS BY MID WEEK. OVERVIEW AND MODEL PREFERENCES... WITH 22.12Z MODEL GUIDANCE CONTINUING TO CONVERGE ON A SOLUTION... AGREE WITH THE LATEST CPC OUTLOOK THAT WARMER THAN USUAL WEATHER WILL RETURN AFTER A COOL START THIS WEEKEND. PREVIOUS SHIFT FORECASTER NOTED THAT THERE IS NOW MUCH BETTER AGREEMENT THAT BERMUDA HIGH AND IT/S SUBTROPICAL RIDGE ARE LIKELY TO GAIN CONTROL OVER THE REGION THROUGH AT LEAST MID WEEK AS LONGWAVE TROF CONTINUES TO RECEDE BACK INTO NE QUEBEC/LABRADOR. THEREFORE... WILL BE CONTINUING THIS TREND THANKS TO BETTER CONFIDENCE IN THE LATEST RUN SOLUTIONS. KIND OF LIKE THE CMC/ECMWF AS A BLEND TO START GIVEN THEIR BETTER CONSISTENCY AND SLIGHTLY LOWER AMPLIFIED SOLUTIONS. HOWEVER...THIS MASS FIELD RIDGE IS ACCOMPANIED BY FAIRLY ROBUST THETA-E RIDGE WITH PWATS NEARLY 3 STD DEVIATIONS ABOVE NORMAL. TO QUOTE W.B. YEATS...THE CENTRE CANNOT HOLD...A DESTABILIZED COLUMN COULD YIELD DIURNAL CONVECTION PARTICULARLY AS A WEAKENING CUTOFF LOW PRES CURRENTLY OVER THE ROCKIES SHIFTS E BY TUE-WED. NEAR NEUTRAL AO/NAO ALSO SUGGEST THE BLOCK WON/T HOLD UP. DETAILS... SUN...MAINLY A REBOUND DAY. THE COLDER TEMPS OF SAT WILL BE GIVING WAY TO MORE MODERATE...SEASONAL TEMPERATURES. H85 TEMPS WILL BE REACHING THE NEAR NORMAL VALUES OF +8C TO +10C. SW WINDS WILL PROMOTE SOME DOWNSLOPING SO WARMER LOCALES OF WRN MA/CT WILL LIKELY APPROACH 80...WHILE THE REMAINING LOCALES REMAIN IN THE 70S. THIS MODERATE W FLOW IS LIKELY ALSO TO LIMIT SEA BREEZE DEVELOPMENT. MON...AS THE UPPER RIDGE BEGINS IT/S BUILDING PROCESS LLJ AND ATTENDANT SFC WARM FRONT WILL BE NOSING IN FROM THE W ON THE PERIPHERY OF THIS RIDGE. SUSPECT ENOUGH MOISTURE CONVERGENCE /PWATS INCREASE TO NEARLY 1.0 INCHES/ AND LIFT ASSOCIATED WITH THIS FEATURE TO YIELD A RISK FOR AFTERNOON -SHRA DEVELOPMENT MAINLY ACROSS INTERIOR WRN MASS/CT. ECHO PREVIOUS FORECASTER THAT IT IS UNLIKELY TO BE A WASHOUT...AND CIPS ANALOGS CONTINUE TO KEEP THE BULK OF THE ACTION TO THE NW. H85 TEMPS WILL INCREASE TO +10C OR +12C...BUT A LITTLE WEAKER MIXING WITH INCREASING CLOUD COVER AHEAD MAY KEEP AMBIENT TEMPS NEAR SEASONAL...BUT WITH INCREASED HUMIDITY AS THE BUILDING THETA-E RIDGE SUGGESTS DWPTS HEADING INTO THE 50S. TUE AND WED...THINGS START TO GET TRICKY HERE. PEAK THETA-E RIDGING AND SLIGHT COOLING AT H5 ARE LIKELY TO YIELD MODERATE MID LVL LAPSE RATES WITHIN THE WARM SECTOR. BUFKIT PROFILES DENOTE VERY HIGH PWATS /NEAR 1.75 INCHES/ ALONG WITH SFC BASED INSTABILITY 500- 1000 J/KG EACH AFTERNOON. STRONGER LLJ AND UPPER LVL DIVERGENCE REMAIN TO THE NW ON TUE...SO SUSPECT MOST CONVECTIVE ACTIVITY REMAINS NW. ON WED...RELOADING OF THE PATTERN AND SECONDARY RIDGE BUILDING BEHIND THE TUE SHORTWAVE MAY MITIGATE AFTERNOON CONVECTIVE ACTIVITY IN SPITE OF THE DESTABILIZED PROFILE. GIVEN THE DIURNALLY DRIVEN INSTABILITY BUT WITH MITIGATING FACTORS...WILL INCREASE POPS TO LOW END CHANCE IN THE W EACH AFTERNOON AS IT/S LIKELY TO BE MORE HIT OR MISS. RETURN FLOW...WITH W COMPONENT AND WARMING MID LVL TEMPS ALL SUGGEST CONTINUOUS TEMPERATURE MODERATION. HIGHS MAY APPROACH THE 90F IN WARM SPOTS. DWPTS IN THE LOW-MID 60S SUGGEST UNCOMFORTABLE HUMIDITY. THU AND FRI...ONCE AGAIN A TRICKY FORECAST HERE. IN THIS CASE...BETTER LOW LVL FORCING IS EXPECTED IN THE FORM OF A MORE ROBUST MID LVL SHORTWAVE AND ATTENDANT COLD FRONTAL PASSAGE. HOWEVER...AT ISSUE IS THE REBOUNDING RIDGE MENTIONED EARLY. THIS WILL LEAD TO AN OVERALL WEAKENING OF THE COLD FRONT/TROF SYSTEM. BUFKIT DOES SHOW SIGNS OF A SUBSIDENCE INVERSION IN PLACE WHICH COULD PRECLUDE AFTERNOON CONVECTION. INSTABILITY STILL SOMEWHAT FAVORABLE...BUT THIS IS A WEEK OUT. WILL NEED TO CONTINUE TO WATCH THIS PERIOD SHOULD THE FRONT SLOW TO A NEAR STALL AS IT INTERACTS WITH THE BUILDING RIDGE. PROVIDING A NEAR STEADY SOURCE OF LIFT FOR THE DESTABILIZED ATMOSPHERE. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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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 FRIDAY/... 00Z UPDATE... WIND GUSTS OF 20-25 KT WILL CONTINUE FOR ANOTHER COUPLE OF HOURS UNTIL THE FRONT CLEARS THE AREA...EXPECT THEM TO LINGER THROUGH ABOUT 02Z. AFTER WHICH THEY WILL ONLY REMAIN ELEVATED AT THE NEAR E COAST TERMINALS. VFR REMAINS IN PLACE. SATURDAY...WEST WINDS UP TO 20 KT IN GUSTS. VFR AND DRY WEATHER PREVAIL. SATURDAY NIGHT...VFR...WITH DIMINISHING WEST WINDS. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...SUNDAY THROUGH WEDNESDAY... SUNDAY INTO MONDAY...HIGH CONFIDENCE. VFR. MAINLY LIGHT W-SW WINDS...WITH SEA BREEZES LIKELY. LOW CHANCE FOR A SHOWER IN WRN MA/CT MON AFTERNOON AND EVENING. TUE AND WED...HIGH CONFIDENCE. MAINLY VFR. ALTHOUGH SOME OVERNIGHT FOG AND STRATUS IS POSSIBLE NEAR COASTLINES...THIS COULD LEAD TO LOCALIZED IFR/MVFR. ALSO...SW FLOW DOMINATES. LOW CHANCE EACH AFTERNOON/EVENING FOR AFTERNOON SHOWERS/TSRA MAINLY IN THE FAR INTERIOR.
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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 /THROUGH SATURDAY/... TONIGHT...COLD FRONT SWEEPS ACROSS THE WATERS WITH WNW WINDS GUSTING UP TO 25 KT. GOOD VSBY. SAT...WNW WINDS 15 TO 20 KT POSSIBLY GUSTING UP TO 25 EARLY BECOMES WSW 15 TO 20 KT DURING THE AFTERNOON. NO PRECIP AND GOOD VSBY. SAT NIGHT...WSW WINDS BRIEFLY DIMINISH BELOW 20 KT. NO PRECIP AND GOOD VSBY. OUTLOOK...SUNDAY THROUGH WEDNESDAY... SUNDAY AND MONDAY...HIGH CONFIDENCE. HIGH PRES WILL MOVE OVER THE WATERS YIELDING PERIOD OF MAINLY QUIET BOATING WEATHER. TUESDAY AND WEDNESDAY...MODERATE CONFIDENCE. WINDS SHIFT TO THE SW...AND INCREASE WITH A FEW NEAR SHORE GUSTS BETWEEN 20 AND 25 KT. EXPECT A SLOWLY BUILDING SW SWELL. THERE MAY BE A NEED FOR SMALL CRAFT ADVISORIES THROUGH THIS PERIOD...BUT NOT THE ENTIRE TIME. SOME MARINE STRATUS AND FOG MAY DEVELOP...REDUCING VISIBILITIES. && .FIRE WEATHER... VERY DRY CONDITIONS EXPECTED SATURDAY...ALONG WITH GUSTY WEST WINDS. WITH THE LACK OF APPRECIABLE RAINFALL ACROSS SOUTHERN NEW ENGLAND LAST NIGHT...AND INFORMATION FROM STATE FIRE OFFICIALS...WILL ISSUE A STATEMENT CONCERNING AN ELEVATED RISK FOR FIRES ACROSS SOUTHERN NEW ENGLAND. && .CLIMATE... RECORD LOWS FOR MAY 23RD... BOSTON - 40 /1967/ HARTFORD - 37 /1976/ PROVIDENCE - 40 /1950/ WORCESTER - 32 /1929/ && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...FROST ADVISORY FROM 2 AM TO 7 AM EDT SATURDAY FOR MAZ004- 009>011-026. FREEZE WARNING FROM 2 AM TO 7 AM EDT SATURDAY FOR MAZ002-003- 008. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EDT SATURDAY FOR ANZ231>235- 237-250-251-254>256. SMALL CRAFT ADVISORY UNTIL 8 AM EDT SATURDAY FOR ANZ230-236. && $$ SYNOPSIS...BELK/DOODY NEAR TERM...BELK/DOODY SHORT TERM...BELK LONG TERM...DOODY AVIATION...BELK/DOODY MARINE...BELK/DOODY FIRE WEATHER... CLIMATE...

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