Area Forecast Discussion
Issued by NWS Boston, MA

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764 FXUS61 KBOX 200124 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 924 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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*** THUNDERSTORMS SLOWLY WEAKENING THIS EVENING ACROSS WESTERN MA AND CT *** 930 PM UPDATE... CONVECTION ACROSS WESTERN MA AND NORTHWEST CT BEGINNING TO WEAKEN AS BOUNDARY LAYER COOLS AND T-STORMS MOVE INTO A MORE STABLE ENVIRONMENT ACROSS EASTERN MA/RI AND CENTRAL-EASTERN MA. THUS TREND OVER THE NEXT FEW HOURS WILL BE FOR CONVECTION TO WEAKEN. MAIN THREATS WITH STORMS WILL BE GUSTY WINDS/SMALL HAIL AND HEAVY RAINFALL. SHOWERS WITH EMBEDDED THUNDER MAY SURVIVE INTO EASTERN CT/RI AND SOUTHEAST MA LATER THIS EVENING...AS APPROACHING SHORT WAVE RESULTS IN HEIGHT FALLS/STEEPENING MID LEVEL LAPSE RATES AND MODEST FORCING FOR ASCENT. 12Z ARW AND NMM CAPTURING THIS WELL AND VERIFYING NICELY AT 00Z. WITH SUNSET BLYR COOLING AS RESULTED IN STRATUS AND FOG REDEVELOPING OVER RI AND SOUTHEAST MA. THIS WILL CONTINUE UNTIL ABOUT 06Z OR SO...THEN COLD FRONT WILL SWEEP ACROSS THIS REGION SCOURING OUT LOW LEVEL MOISTURE WITH GUSTY WNW WINDS BEHIND THE FRONT. PREVIOUS DISCUSSION... 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 /01Z 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/... 930 PM UPDATE... T-STORMS OVER WESTERN MA AND CT WILL CONTINUE TO SLOWLY WEAKEN AS ACTIVITY ENTERS EASTERN CT/RI AND SOUTHEAST MA. A FEW OF THE STRONGER STORMS MAY PRODUCE GUSTY WINDS...SMALL HAIL AND HEAVY RAIN THRU 1030 PM. OTHERWISE WEAKENING TREND CONTINUES WITH JUST SHOWERS ENTERING RI AND SOUTHEAST MA. IFR CONDITIONS IN LOW CLOUDS AND FOG OVER RI AND SOUTHEAST MA WILL IMPROVE AROUND 06Z WITH THE WIND SHIFT TO THE WNW WITH GUSTS UP TO 30 KT POSSIBLE. EARLIER DISCUSSION BELOW. ================================================================= 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... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EDT WEDNESDAY FOR ANZ230>236-250-251. && $$ SYNOPSIS...FRANK/DOODY NEAR TERM...FRANK/NOCERA/DOODY SHORT TERM...FRANK LONG TERM...DOODY AVIATION...FRANK/NOCERA/DOODY MARINE...FRANK/DOODY FIRE WEATHER...

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