Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 192300 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 700 PM EDT TUE MAY 19 2015 .SYNOPSIS... A FEW STRONG THUNDERSTORMS ARE POSSIBLE THIS EVENING ACROSS WESTERN MASSACHUSETTS AND NORTHERN CONNECTICUT IN ASSOCIATION WITH A COLD FRONT. OTHERWISE...DRY AND NICE WEATHER IS ON TAP FOR WEDNESDAY WITH NEAR OR JUST BELOW NORMAL TEMPERATURES. DRY WEATHER RETURNS FOR THURSDAY WITH A FEW SHOWERS POSSIBLE ON FRIDAY AHEAD OF A COLD FRONT. COOLER BUT DRY WEATHER RETURNS FOR THE WEEKEND. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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***A FEW STRONG TO PERHAPS A MARGINALLY SEVERE THUNDERSTORM OR TWO POSSIBLE BETWEEN 7 AND 10 PM ACROSS WESTERN MA/NORTHERN CT*** 7PM UPDATE... LATEST OBS SUGGEST THAT THE COLD FRONT IS JUST NOW MAKING IT INTO THE HUDSON RIVER VALLEY AND CATSKILLS...WITH A BAND OF WEAK CONVECTION MOVING ALONG WITH IT. AHEAD OF THIS FRONT...SOME ISOLATED SVR STORMS HAVE DEVELOPED...BUT CONTINUE TO DIMINISH AS THEY APPROACH SRN NEW ENGLAND...WHICH DESTABILIZED LATE IN THE DAY. BEST INSTABILITY NOW RESIDES MAINLY IN SRN NW AND SW CT THROUGH EXTREME SW MA. SO WILL NEED TO CONTINUE TO WATCH THIS AREA AS THE FRONT MOVES THROUGH...ESPECIALLY THANKS TO NEARLY 40 KT OF 0-6KM SHEAR TO HELP IT ALONG. HOWEVER...AS THE SUN CONTINUES TO SET...SUSPECT WE WILL SEE A GRADUAL END TO THE CONVECTION...WHICH SHOULD BE DONE COMPLETELY BY ABOUT 03-04Z. HAVE TIMED AND ADJUSTED POPS TOWARD THIS THINKING...HIGHLIGHTING MAINLY JUST THE SW PORTIONS OF THE FORECAST AREA THROUGH 04Z. WILL ALSO CONTINUE MENTION OF TSRA/GUSTY WINDS/HEAVY RAIN FOR THE TIME BEING. PREVIOUS DISCUSSION... JUST SOME LEFT OVER SHOWERS ACROSS THE FAR SOUTHEAST NEW ENGLAND COAST AT LATE AFTERNOON. THIS ACTIVITY SHOULD EXIT THE REGION OVER THE NEXT FEW HOURS. MEANWHILE...PARTIAL SUNSHINE HAS DEVELOPED ACROSS OUR WESTERN ZONES. THIS WILL LIKELY ALLOW FOR TEMPS TO SURGE INTO THE 70S TOWARD EVENING. HOWEVER...LOW CLOUDS AND PATCHY FOG WILL REMAIN ENTRENCHED ACROSS THE SOUTHEAST NEW ENGLAND COAST KEEPING TEMPS IN THE UPPER 50S AND 60S. THE MAIN QUESTION BECOMES HOW MUCH INSTABILITY DEVELOPS THIS EVENING ACROSS WESTERN MA/NORTHERN CT AHEAD OF THE PRE-FRONTAL TROUGH/COLD FRONT. BASED ON THE LATEST DATA WE ARE THINKING THAT 500 TO 1000 J/KG OF CAPE DEVELOP TOWARD EVENING. AT THE SAME TIME...0 TO 6 KM SHEAR VALUES ARE INCREASING TO BETWEEN 35 AND 45 KNOTS AS A STRONG SHORTWAVE WORKS INTO THE REGION. THIS SETUP IN SOUTHERN NEW ENGLAND IS RATHER MARGINAL. DESPITE...VERY GOOD SHEAR RATHER MARGINAL INSTABILITY WILL BE A LIMITING FACTOR. IN ADDITION...TIMING LOOKS TO BE BETWEEN 5 AND 10 PM THIS EVENING SO A FEW HOURS AFTER TYPICAL PEAK HEATING/INSTABILITY. ALL IN ALL...NOT REALLY MUCH CHANGE FROM THE PREVIOUS FORECAST. A FEW STRONG THUNDERSTORMS WITH PERHAPS A MARGINALLY SEVERE THUNDERSTORM OR TWO ARE POSSIBLE BETWEEN 6 AND 10 PM THIS EVENING ACROSS WESTERN MA/NORTHERN CT. THE MAIN CONCERN IS VERY LOCALIZED STRONG TO DAMAGING WIND GUSTS WITH HAIL A SECONDARY CONCERN. ACROSS EASTERN NEW ENGLAND...INSTABILITY WILL BE QUITE LIMITED. SO DESPITE GOOD FLOW ALOFT THE ACTIVITY WILL WEAKEN AS IT TRIES TO MOVE EAST. IF ANY ACTIVITY DOES SURVIVE...PROBABLY JUST A FEW SHOWERS ARRIVE ACROSS EASTERN MA/RI LATE THIS EVENING. MUCH DRIER AND COOLER AIR WORKS INTO THE REGION BEHIND THE COLD FRONT AFTER MIDNIGHT. LOW TEMPS BY DAYBREAK WILL BE DOWN INTO THE UPPER 40S TO THE MIDDLE 50S. LEFT OVER LOW CLOUDS/FOG PATCHES WILL SCOUR OUT TOWARD DAYBREAK ACROSS THE FAR SOUTHEAST NEW ENGLAND COAST.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... WEDNESDAY... MUCH DRIER AIR CONTINUES WILL WORK INTO SOUTHERN NEW ENGLAND BEHIND THE COLD FRONT. PARTLY SUNNY SKIES ARE EXPECTED BUT THERE WILL BE SOME SCATTERED DIURNAL CUMULUS CLOUDS ESPECIALLY ACROSS OUR NORTHERN ZONES. 850 MB TEMPS DROP TO BETWEEN 0C AND +4C BY 18Z...BUT THERE WILL BE DEEP MIXING. THEREFORE...EXPECT HIGHS TO REACH WELL INTO THE 60S...WITH PERHAPS A FEW LOCATIONS TOUCHING 70 ACROSS RHODE ISLAND/SOUTHEAST MA. IT WILL BE BLUSTERY AS GOOD MIXING WILL RESULT IN A FEW HOURS OF NORTHWEST WIND GUSTS OF 25 TO 30 MPH DURING THE AFTERNOON. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... */ HIGHLIGHTS... - SEASONABLE AND DRY UNDER HIGH PRESSURE THURSDAY - SWEEPING COLD FRONT FRIDAY - RETURN OF DRY AND COOLER CONDITIONS FOR THE WEEKEND - PERHAPS A RETURN OF WET-WEATHER EARLY NEXT WEEK OVERVIEW AND MODEL PREFERENCES... WITH 19.12Z MODEL GUIDANCE CONTINUING TO SHOW REASONABLY GOOD AGREEMENT THROUGH THE LONG TERM...A BLEND OF OPERATIONAL GUIDANCE AND PERSISTENCE WILL BE USED AS A BASELINE. THERE ARE A FEW TWEAKS TO MAKE. THE LONGWAVE TROF THAT SETTLES ACROSS ERN CANADA AND THE NE CONUS WILL ALLOW FOR A FAIRLY COLD AIRMASS TO ADVECT ACROSS THE REGION WITH A STRONG VORTEX MOVING THROUGH ON FRI...MANIFESTING AS A COLD FRONT. MODEL DWPTS ARE LIKELY TOO HIGH HERE. WHICH MEANS THAT SHOULD THE PRES GRADIENT SLACKEN ENOUGH BOTH FRI AND SAT NIGHTS...MAY NEED TO MONITOR FOR A PERIOD WHERE FROST IS POSSIBLE. ALSO...AS NOTED BY PREVIOUS FORECASTER...THIS DRY AIR WOULD ALSO SUGGEST HIGHER FIRE WEATHER POTENTIAL DEPENDENT ON RAINFALL TODAY/THIS EVENING. DETAILS... WED NIGHT INTO THU NIGHT... MAINLY DRY WX EXPECTED AS HIGH PRES MOVES ACROSS THE REGION. WILL LIKELY SEE SOME PERSISTENT CLOUD COVER AT TIMES THOUGH...GIVEN UPPER LVL CYCLONIC CURVATURE AND MODEST MID LVL MOISTURE. +3C TO +5C H85 TEMPS SHOULD STILL BE REACHED...IF NOT EVEN SLIGHTLY HIGHER. THEREFORE...SUSPECT MAX/MIN VALUES NEAR SEASONAL NORMALS. FRI... FAIRLY ROBUST ARCTIC INFLUENCED VORTEX WILL BE MOVING THROUGH THE BASE OF THE LONGWAVE TROF ACROSS THE NE CONUS AND ERN CANADA. THE SFC REFLECTION IS ITSELF A STRONG COLD FRONT WITH DECENT BAROCLINIC PACKING EVIDENT. THEREFORE...PLENTY OF POTENTIAL FOR LIFT WITH THIS FEATURE AS IT MOVES ACROSS THE REGION FRI. THE LIMITING FACTOR IS MOISTURE AS PREVIOUS LONG TERM FORECASTER NOTED. PWATS REALLY ONLY TOP OUT AROUND 0.60 INCHES. BY THE AFTERNOON. STILL FEEL THE SLIGHT CHANCE POPS ADVERTISED ARE WARRANTED...ESPECIALLY JUST GIVEN HOW HIGH THE LIFT POTENTIAL IS WITH THE FRONT ITSELF. THERE IS A LITTLE BIT OF LOW LVL INSTABILITY INVOF THE BL TO WORK WITH AS WELL. THEREFORE...WILL MAINTAIN PRECIP CHANCES AS THEY STAND FOR THE TIME BEING. FRI NIGHT INTO SAT... AS MENTIONED ABOVE THE KEY FOR THIS TIME PERIOD IS THE POTENTIALLY DRY AND COOL AIRMASS WHICH IS PROGGED TO SETTLE ACROSS THE REGION. IN FACT 1000-500 THICKNESS VALUES ARE SUB 540DAM FOR MUCH OF THE REGION. WITH H85 TEMPS DIPPING BELOW 0C FOR SAT. THEREFORE...WILL NEED TO MONITOR FOR LOW DWPTS AND RH VALUES BY DAY...AND POTENTIALLY NEAR FREEZING TEMPERATURES FOR COLDER VALLEYS AT NIGHT. CONFIDENCE IS NOT HIGH ENOUGH TO ALARM ON FROST POTENTIAL AT THIS POINT GIVEN THERE IS SOME QUESTION IN THE PRES GRADIENT AND WINDS REMAINING ELEVATED...BUT FEEL IT IS AT LEAST WORTH MENTIONING/MONITORING. EARLY NEXT WEEK... SUBTROPICAL RIDGING WILL ONCE AGAIN BE GAINING STRENGTH THROUGH THE PERIOD...ALLOWING FOR A WARMING OF THE COLUMN ACROSS THE NE THROUGH THE PERIOD. ASIDE FROM THE WARMING...INDICATIONS OF A WARM FRONTAL PASSAGE WITH POTENTIAL FOR PRECIP/CONVECTION INDICATED FOR TUES. SOMETHING TO KEEP AN EYE ON. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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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 WEDNESDAY/... THROUGH THE OVERNIGHT HOURS...MODERAT CONFIDENCE. VFR MAINLY W OF A PVD-BOS LINE WILL REMAIN THROUGH THE OVERNIGHT HOURS. THE ONLY CAVEAT WILL BE THE POSSIBILITY OF A BRIEF TSRA/SHRA ESPECIALLY AT TERMINALS IN CT AND EXTREME SW MA. THIS RISK ENDS BY ABOUT 04Z. TO THE E OF THIS LINE. A PERIOD OF IFR/MVFR CONDITIONS PERSISTS IN LOW CLOUDS AND FOG. UNTIL A COLD FRONT MOVES THROUGH MAINLY BETWEEN 04Z-07Z. AFTER WINDS SHIFT TO THE W EXPECT IMPROVEMENT TO VFR WITH WIND GUSTS INCREASING...15-25 KT AT TIMES. WEDNESDAY...HIGH CONFIDENCE. VFR WITH NORTHWEST WIND GUSTS OF 25 KNOTS EXPECTED FOR A FEW HOURS DURING THE AFTERNOON. KBOS TERMINAL...HIGH CONFIDENCE. CONDITIONS IMPROVE WITHIN AN HOUR OR TWO. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. AT ISSUE IS A BRIEF TSRA/SHRA MAINLY BETWEEN 00Z AND 03Z. OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY... WED NIGHT THROUGH FRI...HIGH CONFIDENCE. MAINLY VFR. WINDS SHIFT FROM NW ON THU...TO S-SW ON FRI BEFORE A COLD FRONT MOVES THROUGH. A FEW SHOWERS POSSIBLE FRI...BUT IT/S LIKELY MOST AREAS REMAIN DRY. SEA BREEZES LIKELY THU. SAT AND SUN...HIGH CONFIDENCE. VFR. W WINDS ON SAT...MAY GUST TO ABOUT 25 KT NEAR SHORELINES. WEAKER WINDS ON SUN...WITH SEA BREEZES POSSIBLE.
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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 /TONIGHT THROUGH TUESDAY NIGHT/... TONIGHT...MODERATE TO HIGH CONFIDENCE. MAIN CONCERN WILL BE FOR AREAS OF FOG ACROSS OUR SOUTHERN WATERS FOR THE FIRST PART OF THE NIGHT...SOME OF WHICH MAY BE LOCALLY DENSE. OTHERWISE...SOUTHWEST WINDS AT 10 TO 15 KNOTS WILL SHIFT TO THE NORTHWEST AFTER MIDNIGHT BEHIND A STRONG COLD FRONT. SOME GUSTS INTO THE LOWER 20 KNOTS ARE EXPECTED WITH PRESSURE RISES BEHIND THE FRONT. WEDNESDAY...HIGH CONFIDENCE. A FEW HOURS OF NORTHWEST WIND GUSTS OF 25 KNOTS EXPECTED NEAR SHORE WITH DEEP MIXING OVER THE LAND. HAVE HOISTED SCA HEADLINES MAINLY FOR OUR NEAR SHORE WATERS. STRONGEST WINDS LOOK TO BE ACROSS OUR EASTERN ZONES...SO DID LEAVE OUT BLOCK ISLAND SOUND OUT FOR NOW. OUTLOOK...WEDNESDAY NIGHT THROUGH SUNDAY...HIGH CONFIDENCE. WED NIGHT INTO FRI... WINDS AND SEAS GENERALLY REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH THIS PERIOD. WINDS WILL BE SHIFTING FROM NW...TO S-SW BY FRI. SEA BREEZES LIKELY ALONG THE COAST. SAT... WINDS WILL INCREASE OUT OF THE W ON SATURDAY SUCH THAT GUSTS MAY APPROACH 25 KT IN THE AFTERNOON. SMALL CRAFT ADVISORIES MAY BE NEEDED. SUN... ANOTHER ROUND OF QUIET BOATING WEATHER WITH HIGH PRES. && .FIRE WEATHER... WEDNESDAY... NORTHWEST WIND ARE EXPECTED TO GUST BETWEEN 25 AND 30 MPH FOR A FEW HOURS WEDNESDAY AFTERNOON. IN ADDITION...MINIMUM AFTERNOON RELATIVE HUMIDITY VALUES ARE EXPECTED TO DROP TO BETWEEN 25 AND 30 PERCENT IN A WELL MIXED ATMOSPHERE. RAINFALL AMOUNTS VARIED CONSIDERABLY TODAY IN SHOWERS. MANY LOCATIONS IN CT/RI AND SOUTHEAST MA RECEIVED NEAR OR MORE THAN 0.25 INCHES OF RAIN WITH LOWER AMOUNTS TO THE NORTH. AFTER COLLABORATING WITH OUR FIRE WEATHER PARTNERS...WILL GO AHEAD AND ISSUE A SPECIAL WEATHER STATEMENT FOR JUST MASSACHUSETTS. THIS IS WHERE THE LEAST AMOUNT OF RAIN FELL TODAY. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EDT WEDNESDAY FOR ANZ230>236-250-251.
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&& $$ SYNOPSIS...FRANK/DOODY NEAR TERM...FRANK/DOODY SHORT TERM...FRANK LONG TERM...DOODY AVIATION...FRANK/DOODY MARINE...FRANK/DOODY FIRE WEATHER...

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