Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 271821 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 211 PM EDT MON JUL 27 2015 .SYNOPSIS... RISK OF SHOWERS AND THUNDERSTORMS CONTINUES THROUGH TUESDAY. STORMS MAY PRODUCE HEAVY RAIN AND A FEW MANY BECOME STRONG TO SEVERE. HOT AND HUMID TUESDAY THROUGH THURSDAY. A COLD FRONT MAY BRING SCATTERED THUNDERSTORMS LATE THURSDAY AND THURSDAY NIGHT. WARM AND DRY WEATHER IS EXPECTED FRIDAY INTO NEXT WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... ***FOCUS FOR SHOWERS AND THUNDERSTORMS WITH TORRENTIAL RAINFALL AND LOCALIZED FLOODING SHIFTING INTO INTERIOR SOUTHERN NEW ENGLAND*** THE EARLIER SHOWERS AND THUNDERSTORMS THAT PRODUCED LOCALLY HEAVY RAINFALL AND STREET FLOODING ALONG THE SOUTH COAST THIS MORNING HAS PRETTY MUCH FALLEN APART. BETTER FORCING AND SURFACE CONVERGENCE HAS LIFTED NORTH OF THAT REGION. MAIN ACTION WAS NOW DEVELOPING ACROSS NORTHERN MA WHERE THERE WAS SOME SURFACE CONVERGENCE MLCAPES WERE ON THE ORDER OF 1500 J/KG. THIS IS THE AREA WE ARE MOST CONCERNED ABOUT FOR LOCALIZED HEAVY RAINFALL/STREET FLOODING...WITH EVEN AN ISOLATED POCKET OR TWO OF FLASH FLOODING POSSIBLE. WE HAVE BEEN WATCHING A CELL JUST SOUTH OF ASHFIELD MA...WHICH HAS BEEN NEARLY STATIONARY WITH DOPPLER RADAR ESTIMATING UP TO 3 INCHES OF RAIN PER HOUR! WILL ALSO HAVE TO WATCH SOUTHWEST MA AND NORTHERN CT FOR SCATTERED SHOWERS AND EMBEDDED THUNDERSTORMS WITH LOCALLY HEAVY RAINFALL...AS THIS AREA IS ALSO DESTABILIZING. TO THE SOUTHEAST OF I-95 A FEW SHOWERS AND PERHAPS AN ISOLATED THUNDERSTORM IS STILL POSSIBLE THROUGH EARLY EVENING...BUT THE ATMOSPHERE HAS BEEN WORKED OVER SO NOT EXPECTING MUCH MORE THAN THAT. WHILE LOCALIZED FLOODING WILL BE OUR MAIN CONCERN... SEVERE WEATHER THREAT WILL BE RATHER LIMITED GIVEN VERY WEAK 0 TO 6 KM SHEAR. HOWEVER...AN ISOLATED SEVERE THUNDERSTORM OR TWO CAN NOT BE RULED OUT GIVEN DECENT MLCAPES WITH 500 MB TEMPS AROUND -11C WHICH IS RATHER CHILLY FOR OUR CURRENT AIRMASS AT THE SURFACE. HIGH TEMPS THIS AFTERNOON WILL MAINLY BE IN THE UPPER 70S TO THE MIDDLE 80S. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... TONIGHT... A REPEAT OF LAST NIGHT ANTICIPATED. SCATTERED SHOWER / THUNDERSTORM ACTIVITY WILL SHIFT E/SE WITH THE MEAN WIND SLOWLY. WHILE DAYTIME HEATING CONCLUDES...THERE STILL IS A LOT OF INSTABILITY AVAILABLE WITHIN THE LOW-MID LEVELS ALOFT WHERE LAPSE RATES ARE CONDITIONALLY UNSTABLE. THREATS OF HEAVY RAIN AND FREQUENT LIGHTNING CONTINUE AND WITH THE SLOW MOVEMENT OF THE STORM THERE IS A CONCERN FOR LOCALIZED FLOODING. A MUGGY NIGHT IN STORE WITH LOWS IN THE MID- TO UPPER- 60S. STORM ACTIVITY MAY DISSIPATE TOWARDS MORNING. TUESDAY... CONTINUED MID-LEVEL ENERGY THROUGH THE BROADER CYCLONIC FLOW ON WHAT APPEARS TO BE NNW-SSE FRONTAL BOUNDARY WHEN EVALUATING THE LOW- TO MID-LEVEL THERMAL PROFILE. SEEMS TO BE SOME LEVEL OF ENHANCED ASCENT THROUGH THE ATMOSPHERIC LAYER. COLLOCATED JET STREAK AND DECENT NNW- SSE UNIDIRECTIONAL BULK SHEAR WITH LAPSE RATES EXCEEDING 6C/KM. SURFACE REFLECTION OF A CONVERGENT BOUNDARY ALONG THE E-COASTLINE OF NEW ENGLAND APPEARS PLAUSIBLE. WITH A WARM MUGGY AIRMASS STILL IN PLACE MAY BE DEALING WITH SHOWER / THUNDERSTORM ACTIVITY ACROSS E- HALF OF NEW ENGLAND...POTENTIALLY LINE-CONVECTION ALONG THE LEADING EDGE OF THE MID-LEVEL IMPULSE. CONSIDERING SHEAR / INSTABILITY / INVERTED-V PROFILES WITHIN THE BOUNDARY-LAYER COULD BE LOOKING AT A MULTI-THREAT OUTCOME WITH ANY CONVECTION AS IT WOULD APPEAR. GOING TO HAVE TO TAKE A LOOK AT THIS MORE CLOSELY OVER THE NEXT 24-HOURS. COLLABORATING WITH OTHER WEATHER FORECAST OFFICES...WILL GO WITH ENHANCED WORDING OF HEAVY RAIN / GUSTY WINDS / SMALL HAIL. GOOD DEEP- LAYER FORCING AND NEAR A LOBE OF H5 COLDER AIR DROPPING S WITH THE MID-LEVEL VORTEX. WITH ANTICIPATED WEATHER / CLOUD COVER PERHAPS SOME ISSUES WITH HIGH TEMPERATURES. MAYBE AN ONSHORE FLOW ALONG THE E-COAST IF THE ZONE OF CONVERGENCE HOLDS OVER THE E-HALF OF NEW ENGLAND. WILL LEAN COOLER IN THIS AREA BUT GO INTO THE UPPER-80S TO THE W. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... HIGHLIGHTS... * TRIPLE-H WEATHER WED/THU WITH HIGHS IN 90S. * SCATTERED STORMS THU/THU NIGHT. * DRIER BUT STILL VERY WARM FRI THRU SUN. LARGE SCALE PATTERN FEATURES BUILDING RIDGE OVER NORTHEAST WED/THU WHICH WILL BRING OUR NEXT SHOT OF HEAT AND HUMIDITY. HOWEVER THIS SHOULD BE RELATIVELY SHORT LIVED AS UPPER LOW DIGS ACROSS CANADIAN PRAIRIES AND EVENTUALLY BECOMES CENTERED NEAR HUDSON BAY...RESULTING IN MORE IN WAY OF CYCLONIC FLOW FOR LATER THIS WEEK INTO NEXT WEEKEND. STILL LOOKS SUMMERLIKE BEYOND THU BUT CHANGE IN UPPER AIR PATTERN SHOULD BREAK HUMIDITY AND KEEP TEMPERATURES CLOSER TO AVERAGE FOR LATE JULY. WED INTO THU...HIGH CONFIDENCE. RISING HEIGHTS SHOULD SUPPRESS CONVECTION WED SO AM CONTINUING WITH DRY FORECAST. NAM SUGGESTION OF DEVELOPMENT ALONG SEA BREEZE FRONT IS POSSIBLE BUT IS OUTLIER AT THIS POINT. HIGHS SHOULD TOP OUT IN LOW TO MID 90S AWAY FROM S COAST BUT WITH DEWPOINTS IN MID 60S TO AROUND 70 HEAT INDICES WILL PROBABLY FALL SHORT OF ADVISORY CRITERIA /100F FOR 2+ HOURS/. ANOTHER HOT/HUMID DAY EXPECTED THU BUT HIGHS SHOULD BE SLIGHTLY LOWER THAN WED GIVEN INCREASING CLOUD COVER AHEAD OF COLD FRONT APPROACHING FROM GREAT LAKES. DECENT CAPE/0-6KM SHOULD BE PRESENT ALONG WITH MARGINAL MID LEVEL LAPSE RATES...SO BETTER CHANCE OF SHOWERS/STORMS DURING AFTERNOON AND EVENING AS FRONT PROVIDES FOCUS FOR LIFT. FRI THROUGH SUN...MODERATE CONFIDENCE. HIGH PRESSURE BUILDS ACROSS NORTHEAST AS UPPER FLOW BECOMES MORE CYCLONIC. THIS WILL BRING SOME RELIEF FROM HEAT/HUMIDITY BUT HIGHS SHOULD STILL TOP OUT WELL INTO 80S AWAY FROM S COAST. GOING WITH DRY FORECAST AS ENSEMBLES SHOW FAIRLY LOW PROBABILITIES OF MEASURABLE RAINFALL DURING THIS TIME FRAME. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY AFTERNOON/... THIS AFTERNOON...MODERATE TO HIGH CONFIDENCE. MAINLY VFR EXCEPT LOCALIZED IFR TO LIFR CONDITIONS IN SCATTERED HEAVIER SHOWERS AND THUNDERSTORMS. MAIN FOCUS IS ACROSS INTERIOR SOUTHERN NEW ENGLAND AND ESPECIALLY IN NORTHERN MA. TONIGHT...LOW TO MODERATE CONFIDENCE. DIURNALLY DRIVEN SCATTERED SHOWERS AND THUNDERSTORMS SHOULD DIMINISH THIS EVENING. WHILE DRY WEATHER PROBABLY DOMINATES MOST LOCATIONS OVERNIGHT...A NARROW BAND OR TWO OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS MAY AFFECT PORTIONS OF EASTERN NEW ENGLAND FOR A TIME. OTHERWISE...MAIN CONCERN OVERNIGHT WILL BE FORMATION OF LOW CLOUDS AND FOG. TIMING UNCERTAIN...BUT WILL HAVE TO WATCH FOR LOCALLY DENSE FOG DEVELOPING OVERNIGHT ESPECIALLY ACROSS THE INTERIOR. TUESDAY...MODERATE TO HIGH CONFIDENCE. ANY LOW CLOUDS AND FOG PATCHES SHOULD IMPROVE TO VFR BY LATE MORNING. OTHERWISE...MAIN CONCERN IS SCATTERED SHOWERS/THUNDERSTORMS THAT ARE EXPECTED TO DEVELOP MAINLY ACROSS EASTERN NEW ENGLAND. WHILE ACTIVITY WILL BE HIT AND MISS...THE POTENTIAL IS THERE FOR ISOLATED STRONG TO SEVERE STORMS WITH LOCALLY HEAVY RAINFALL. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. MAINLY VFR THROUGH TONIGHT BUT WILL HAVE TO WATCH FOR A THUNDERSTORM IN THE VICINITY OF THE TERMINAL. HIGHEST RISK IS NORTH OF THE AIRPORT...BUT IT IS POSSIBLE IN BOSTON AS WELL. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. MAINLY VFR THROUGH THIS EVENING BUT WILL HAVE TO WATCH FOR A THUNDERSTORM IN THE VICINITY OF THE TERMINAL. LOW CLOUDS AND SOME FOG MAY DEVELOP LATE TONIGHT. OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/... TUESDAY NIGHT AND WEDNESDAY...HIGH CONFIDENCE. MVFR/IFR IN SCT SHRA/TSRA TUESDAY EVENING...OTHERWISE VFR. THURSDAY...MODERATE CONFIDENCE. MVFR/IFR IN SCT SHRA/TSRA MAINLY DURING AFTERNOON AND EVENING. FRIDAY...MODERATE CONFIDENCE. VFR. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY AFTERNOON/...HIGH CONFIDENCE. WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH TUESDAY AFTERNOON. A FEW SPOT SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE THROUGH TONIGHT. HOWEVER...A BETTER CHANCE OF A FEW STRONG TO SEVERE THUNDERSTORMS TUESDAY AFTERNOON WHICH MAY RESULT IN BRIEFLY STRONG WIND GUSTS AND HAIL. SPECIAL MARINE WARNINGS MAY BE NEEDED. OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/... TUESDAY NIGHT AND WEDNESDAY...HIGH CONFIDENCE. WINDS AND SEAS REMAIN BELOW SCA. SCA. MAY SEE LEFTOVER SHOWERS/STORMS ON WATERS DURING EVENING. THURSDAY...MODERATE CONFIDENCE. INCREASING S/SW WINDS EXPECTED AHEAD OF COLD FRONT...BUT GUSTS SHOULD PEAK AROUND 20KT MAINLY ON S COASTAL WATERS. BUILDING S SWELL MAY REACH 5 FT ON OUTER WATERS S OF ISLANDS. MAY SEE THUNDERSTORMS LATER IN DAY AND THU EVENING. FRIDAY...MODERATE CONFIDENCE. HIGH PRESSURE BUILDS OVER WATERS. WINDS AND SEAS BELOW SCA. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...SIPPRELL/JWD NEAR TERM...FRANK SHORT TERM...SIPPRELL LONG TERM...JWD AVIATION...FRANK/JWD MARINE...FRANK/JWD

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