Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 260744 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 344 AM EDT SUN JUL 26 2015 .SYNOPSIS... UNSETTLED WEATHER EXPECTED THROUGH EARLY NEXT WEEK...WITH MAINLY DIURNAL SHOWERS AND THUNDERSTORMS. SCATTERED STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE AGAIN SOMETIME SUNDAY INTO SUNDAY NIGHT. RISK FOR THUNDERSTORMS CONTINUES MONDAY. THE NEXT MAIN WEATHER HEADLINE WILL BE A POSSIBLE HEAT WAVE TUESDAY THROUGH THURSDAY. A COLD FRONT MAY BRING SCATTERED THUNDERSTORMS LATE THURSDAY AND THURSDAY NIGHT. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
INTO THIS MORNING... WARM FRONT ALONG THE LEADING EDGE OF A NOSE OF WARM / HIGH THETA-E AIR IS PUSHING E ACROSS THE NE-CONUS. STRONG CONVERGENCE AND DECENT FORCING NOT OUT OF THE QUESTION IN AN ENVIRONMENT OF NOTEWORTHY 0-1/0-3 KM HELICITY AS E/SE-FLOW WITHIN THE LOW-LEVELS MEETS UP WITH PREDOMINANT W-FLOW ALOFT. BUT IT APPEARS BETTER INSTABILITY LAGS PER SPC MESOANALYSIS AS THE BULK OF THUNDERSTORMS HAS HELD WELL TO THE W. NEVERTHELESS MUCH OF THE ENVIRONMENT LOOKS TO TRANSLATE E SO ALL POTENTIAL FACTORS NEED TO BE TAKEN INTO CONSIDERATION. A LIKELY EXPECTATION OF WET WEATHER TO PUSH E THOUGH THE OUTER EDGE MAY FACE SOME WEAKENING / EROSION UP AGAINST THE DRIER AND SUBSIDING AIRMASS TO THE E...SEE 0Z SOUNDINGS OUT OF GRAY AND CARIBOU MAINE. NEVERTHELESS FEEL THE STRONG FORCING ALONG THE WARM FRONT SHOULD PUSH RAIN INTO THE AREA BY MORNING WITH EMBEDDED HEAVIER SHOWERS...PERHAPS SOME THUNDERSTORMS. FEEL THE S-FLANK OF THE LINE IS BEING FED BY BETTER THETA-E AND INSTABILITY. PERHAPS THE AFOREMENTIONED RIDGING AND DRY AIR TO THE E IS NOTEWORTHY... BUT NOT THINKING IT IS GOING TO BE ENOUGH TO STOP THE TRAIN. FORECAST WAS A BLEND OF HRRR/SREF BLENDS WITH MOS GUIDANCE. STRAYED FROM EXPLICIT NAM/WRF MODEL SOLUTIONS. LIKELY POPS ACCORDINGLY. TODAY... MID-LEVEL IMPULSE AND ACCOMPANYING WARM-FRONTAL BOUNDARY LIFT N/E INTO MAINE. LOW- TO MID-LEVEL FORCING ALONG THE NOSE OF HIGH THETA-E AIR WILL CONTINUE RESULTING IN LIKELY WET-WEATHER IN THE FORM OF WIDESPREAD SHOWERS AND PERHAPS SOME THUNDERSTORMS ACROSS MUCH OF S NEW ENGLAND. A CONTINUED HIGH SHEAR / LOW INSTABILITY ENVIRONMENT. FOCUS TURNS TO THE W FOR THE MIDDAY INTO AFTERNOON PERIOD. LAGGING CONVERGENT BOUNDARY SW-NE PARENT TO A WEAK LOW- TO MID-LEVEL TROUGH. HIGH THETA-E / THERMAL AXIS FROM THE SW ACROSS THE INTERIOR ALONG AND AHEAD. APPEARING AS A HIGH INSTABILITY / LOW SHEAR EVENT WITH INSTABILITY VALUES AROUND 1-2K J/KG. CONSIDERING TRIGGERS OF LOW- LEVEL CONVERGENCE / OROGRAPHIC INFLUENCES / DESTABILIZATION WITH A PWAT ENVIRONMENT AROUND 1.25-1.50 INCHES WITH A WESTERLY MEAN-WIND OF AROUND 15 KTS...LOOKING AT THREATS OF LARGE HAIL / HEAVY RAIN / STRONG TO DAMAGING WINDS. FOCUS IS MAINLY OVER THE N/W/CENTRAL-AREAS OF S NEW ENGLAND WHERE CLOUD DEBRIS LOOKS TO CLEAR ALLOWING STORM DEVELOPMENT. CAN NOT RULE OUT SOME LOCALIZED FLOODING. GAINING A MEASURE OF CONFIDENCE...SREF PROBABILITY GUIDANCE HIGHLIGHTS THE LIKELIHOOD OF INSTABILITY OVER W NEW ENGLAND SEPARATED FROM HIGH-VALUES OF EFFECTIVE BULK SHEAR TO THE E AND OFFSHORE. CONVECTIVE OUTCOMES WITH A LEVEL OF SEVERITY APPEAR LIKELY. SO WILL GO WITH MORNING WIDESPREAD RAIN WITH EMBEDDED HEAVY SHOWERS WITH LESSER WORDING CONCERNING THUNDERSTORMS SWEEPING S NEW ENGLAND AND LIFTING OUT OF THE REGION TOWARDS MIDDAY. TO THE W THERE IS AN OPPORTUNITY FOR DESTABILIZATION ALONG A CONVERGENT BOUNDARY YIELDING A LINE OF THUNDERSTORMS TO DEVELOP THAT SHOULD PROGRESS E/SE. THERE IS THE POTENTIAL FOR SUCH STORMS TO BE STRONG TO SEVERE WITHIN A WEAK TO MODERATE SHEAR GRADIENT W TO E IN AN ENVIRONMENT OF DEEP- LAYER THIN TO MODEST CAPE AS DERIVED FROM SREF PROBABILITIES. MUGGY AIRMASS IN PLACE WITH ONSHORE S-FLOW AS HIGHS WARM INTO THE UPPER-70S TO LOW-80S.
-- End Changed Discussion --
&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
-- Changed Discussion --
TONIGHT.... SCATTERED SHOWER / THUNDERSTORM ACTIVITY SHIFTING E/SE WITH THE MEAN WIND IN A CONTINUED ZONE OF LOW-LEVEL CONVERGENCE / LOWER PRESSURE. WITH DAYTIME HEATING ABSENT...STORMS SHOULD BE ON A DOWNWARD TREND. NO MORE FUEL TO THE FIRE. CONVECTIVE THREATS MAY LINGER INTO THE EVENING HOURS BUT SHOULD TRANSLATE INTO LIGHT SHOWERY WEATHER FOR THE OVERNIGHT PERIOD. OTHERWISE SOME CONCERN AS TO PATCHY DENSE FOG. EXPECT CLOUDS TO LINGER WITH MODEST S-WINDS...BUT COULD BE SOME CHANCES OVER N-PORTIONS OF S NEW ENGLAND WHERE CLEARING IS POSSIBLE UNDER LIGHT WINDS. LOWS IN THE 60S. MONDAY... LOWER PRESSURE ACROSS THE NE-CONUS ORIENTED WITH A THERMAL / THETA-E AXIS FROM THE SW CONTINUES. ANOTHER HIGH INSTABILITY/LOW-SHEAR SETUP IS ANTICIPATED. AIRMASS SHOWERS/THUNDERSTORMS ARE EXPECTED WHEREVER THE ATMOSPHERE DESTABILIZES AND/OR THERE IS LOCALIZED CONVERGENCE. BOUNDARY IS LESS DEFINED SO NOT THINKING AS SCATTERED TO WIDESPREAD AS TODAY BUT RATHER ISOLATED TO SCATTERED. WITH THE MEAN WIND FLOW AROUND 10 MPH OUT OF THE W...THREATS CONSIDERED ARE HEAVY RAIN / LARGE HAIL / PERHAPS STRONG TO DAMAGING WINDS AS STORM-CORES DROP OUT DUE TO THE WEAK-SHEAR ENVIRONMENT /POOR UPDRAFT MAINTENANCE/. WILL NEED TO MONITOR FOR ADDITIONAL STORM DEVELOPMENT ALONG ANY COLD POOLS AS STORMS POTENTIALLY DROP OUT AS WELL AS ALONG HIGH TERRAIN. ALSO POTENTIAL LOCALIZED FLOODING. HIGHS INTO THE THE MID- TO UPPER- 80S AWAY FROM THE COAST BENEATH THE WARM AND MUGGY AIRMASS.
-- End Changed Discussion --
&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... HIGHLIGHTS... * SCATTERED T-STORMS MONDAY. * HEAT WAVE POSSIBLE TUESDAY THROUGH THURSDAY. * SCATTERED STORMS POSSIBLE LATE THURSDAY AND THURSDAY NIGHT. OVERVIEW AND MODEL PREFERENCES... FINALLY WE WILL BE MOVING ONE CUTOFF LOW PRES ACROSS ATLANTIC CANADA OUT TOWARD GREENLAND...ALLOWING SUBTROPICAL RIDGING TO TAKE CONTROL THROUGH MUCH OF THE WEEK. FOLLOWED BY YET ANOTHER ONE. GUIDANCE IN PRETTY GOOD AGREEMENT AT THE SYNOPTIC SCALE WITH THIS THINKING. THEREFORE...HAVE HIGH CONFIDENCE IN ECHOING PREVIOUS FORECASTER THAT A HEAT WAVE FOR SOME /OR AT THE VERY LEAST ABOVE NORMAL TEMPERATURES/ IS LIKELY FOR THE TUE-FRI TIMEFRAME. UNCERTAINTY IN TIMING OF ANY PRECIP PARTICULARLY TUE- FRI AS WELL...AS GUIDANCE CONTINUES TO INDICATE QPF BUT IN AN UNFAVORABLE REGIME. FEEL THAT AS A SECONDARY CUTOFF SETTLES ACROSS QUEBEC AND NRN NEW ENGLAND THE THREAT FOR PRECIP WILL INCREASE...BUT THE MID TERM IS LIKELY TO BE MORE DRY THAN WET...WITH THE ONE EXCEPTION BEING MON...BUT MORE ON THAT BELOW. GIVEN THE REASONABLE SYNOPTIC AGREEMENT...A BLEND OF OPERATIONAL GUIDANCE AND ENSEMBLES WILL BE USED. THIS SHOULD ALSO SMOOTH OUT ANY OF THE QPF ANOMALIES MENTIONED ABOVE. DETAILS... MON... GFS HAS NOW JOINED THE ECMWF AND INDICATES HIGHER K-INDICES AND MODEST P-WATS AVAILABLE TO WORK WITH A STALLED AND DISSIPATING FRONT ACROSS SRN NEW ENGLAND MON. THIS INCREASE IN MOISTURE LEADS TO DECENT SFC BASED CAPE VALUES APPROACHING 1500-2000J/KG UNDER NEARLY 6.5C/KM LAPSE RATES. AT ODDS WILL BE HOW MUCH CLEARING IS OBSERVED AND WHETHER THE BULK OF THIS CAPE CAN EVEN BE REALIZED IN SPITE OF THE FORCING MECHANISM. BEST CHANCE WILL BE WRN MA/CT WHERE DRIER AIR WILL BE MOVING IN...BUT THIS WILL ALSO LEAD TO SOME CAPPING. THEREFORE...NOT AN IDEAL SETUP HERE...SHEAR NOT IMPRESSIVE EITHER AND WILL LIKELY BE TOO LOW TO MAKE UP THE DIFFERENCE. IN ANY CASE...LOW END CHANCE POPS WITH SOME MENTION OF THUNDER STILL SEEMS LIKE A REASONABLE FORECAST FOR MON...PRIOR TO THE HEATING OF MID WEEK. TUE THROUGH THU... BUILDING RIDGE WILL ALSO LEAD TO INCREASING LOW-MID LVL TEMPS THROUGH THE PERIOD. H92 TEMPS START AROUND 22-23C AND H85 16-17C. BY THU...THEY TOP OUT AROUND 26-28C AT H92 AND 20-22C AT H85. THIS SUGGESTS A CAP WHICH IS LIKELY TO PREVENT DEVELOPMENT DIURNAL CONVECTION AND WITH LIMITED PWATS /NEAR JULY NORMALS/ TUE AND WED...SUSPECT SOUNDING IS TOO DRY TO SUPPORT THE QPF THAT THE GFS IS ESPECIALLY ROBUST WITH. BY THU HUMIDITY/PWATS INCREASE TO NEARLY 2 STD DEVIATIONS ABOVE NORMAL BUT DEEP LAYER RIDGING AND CONTINUED CAPPING SHOULD LIMIT RISK FOR SHOWERS/STORMS. THEREFORE...WILL GO WITH A MAINLY DRY PERIOD...BUT WITH GRADUALLY MODERATING TEMPERATURES. W COMPONENT TO THE FLOW DOES INDICATE DOWNSLOPING...SO TEMPERATURES ARE LIKELY TO OVERACHIEVE TYPICAL MIXING EACH DAY. SOME LOCATIONS COULD BE HEADING FOR A TRUE HEAT WAVE...BUT SEVERAL LOCATIONS WILL LIKELY SEE THE LOW 90S BY THU. FRI... THE FIRST IN A SERIES OF SHORTWAVES WHICH WILL HELP TO DIG A CUTOFF LOW PRES AND ASSOCIATED TROF TO THE S MOVES THROUGH ON FRI. TIMING DIFFERENCES ARE NOTED WITH TYPICAL BIASES...AS IN GFS IS FASTER THAN THE THE MORE AMPLIFIED ECMWF. FOR NOW...WILL TIME THE ATTENDANT FRONTAL BOUNDARY RIGHT DOWN THE MIDDLE OF THESE SOLUTIONS...SUGGESTING A LATE THU NIGHT/EARLY FRI PASSAGE. RISK FOR THUNDERSTORMS WILL BE DEPENDENT ON EROSION OF THE CAP AND LEFTOVER CAPE VALUES DURING THE OVERNIGHT HOURS. ONCE AGAIN SHEAR IS LIMITED...SO WILL BE INCREASING POPS BUT APPLYING THUNDER UNDER THE HIGHEST POP THRESHOLD. INDEED EVEN MODELS CAPABLE OF RESOLVING CONVECTION ARE NOT OVERLY IMPRESSIVE AT THIS POINT. HOWEVER...GIVEN THE AIRMASS IN PLACE ABOVE THE CAP...WILL NEED TO KEEP AN EYE ON THIS PERIOD...AS A LATER PASSAGE COULD MEAN SOMETHING ENTIRELY DIFFERENT. SAT... WILL GENERALLY LEAN ON A DRY PERIOD...BUT WITH THE SETTLING CUTOFF AND NEAR STALLING FRONTAL BOUNDARY TO THE S...THIS TOO COULD CHANGE. AT ANY RATE...COOLER AIRMASS IN PLACE WITH TEMPERATURES TRENDING BACK TOWARD SEASONAL NORMALS. && .AVIATION /07Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH MONDAY/... TOWARDS 12Z... RAIN PUSHES E INTO W NEW ENGLAND WITH MAINLY EMBEDDED +RA... POSSIBLE TSRA. TEMPO MVFR-IFR POSSIBLE WITH +RA. SE-WINDS. PATCHY DENSE FOG SHOULD ERODE. LOW-END VFR CIGS EXPECT ACK WHERE PERHAPS IFR HOLDS. TODAY... RAIN LIFTS N/E THROUGH MIDDAY WITH EMBEDDED +RA/TSRA AND TEMPO MVFR- IFR IMPACTS. LOW-END VFR PREVAILS THOUGH BRIEF. SHRA/TSRA DEVELOP TO THE W...SOME POSSIBLY STRONG TO SEVERE. HAIL / WINDS / LIGHTNING. AWW/S MAY BE NEEDED. INCREASING S-WINDS. TONIGHT... SHRA/TSRA MAINLY W DISSIPATE AS THEY DRIFT S/E TOWARDS THE COAST DURING THE EVENING HRS. -SHRA OVERNIGHT. CONTINUED S-WINDS WITH POSSIBLE PATCHY IFR-LIFR DENSE FOG IN SPOTS MONDAY... IMPROVING LOW-END VFR. SCT SHRA/TSRA DEVELOPING ACROSS THE INTERIOR SOME OF WHICH MAY BE STRONG TO SEVERE WITH TEMPO MVFR-IFR IMPACTS. HAIL / WINDS / LIGHTNING. AWW/S MAY BE NEEDED. BREEZY S /SW-WINDS. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. LOW-END VFR CIGS. PERHAPS SOME TEMPO MVFR WITH RAIN PUSHING THRU DURING MIDDAY. FEEL BETTER SHRA/TSRA MAY HOLD W OF TERMINAL DURING AFTERNOON. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. LOW-END VFR WITH RAIN THIS MORNING EXITING BY MIDDAY. AFTERNOON PROGGED WITH SCT SHRA/TSRA THOUGH UNCERTAIN IF DIRECT IMPACT. OUTLOOK /MONDAY THROUGH THURSDAY/... MON AND TUE...MODERATE CONFIDENCE. A FRONTAL BOUNDARY WILL STALL OVER...OR JUST OFFSHORE OF NEW ENGLAND. THIS WILL PROVIDE A FOCUS FOR CONTINUED SHOWER/T-STORMS DURING THE AFTERNOON HOURS. OTHERWISE VFR DURING THE DAY. FOG POSSIBLE AT TYPICALLY PRONE AIRPORTS EACH NIGHT. WED AND THU...HIGH CONFIDENCE. MAINLY VFR WITH WEAK HIGH PRES.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH MONDAY/...HIGH CONFIDENCE. TODAY... PERIODS OF WET-WEATHER WITH THE POSSIBILITY OF THUNDERSTORMS BY AFTERNOON CLOSER TO THE S-WATERS. SE-WINDS VEERING S WITH GUSTS UP TO AROUND 20 KTS. SEAS REMAINING BELOW 4-FEET. TONIGHT... WET-WEATHER CHANCES CONTINUING WITH THUNDER POTENTIAL DIMINISHING THROUGH THE EVENING HOURS. S-WINDS CONTINUING WITH THE POTENTIAL FOR GUSTS UP AROUND 20 KTS. SEAS BELOW 4-FEET. MONDAY... WET-WEATHER MAY HOLD MORE ACROSS THE INTERIOR THAN OVER THE WATERS AS BREEZY S-WINDS CONTINUE WITH THE POTENTIAL FOR GUSTS UP 15 KTS. SEAS REMAINING BELOW 4-FEET THE HIGHEST OF WHICH ARE ANTICIPATED OVER THE E/NE-WATERS. OUTLOOK /MONDAY THROUGH THURSDAY/... MON AND TUE...HIGH CONFIDENCE. A FRONTAL BOUNDARY WILL STALL OVER OR JUST INLAND OF THE SRN NEW ENGLAND WATERS...THEN MOVE OFFSHORE ON TUE. THIS BOUNDARY IS LIKELY TO HAVE LITTLE IMPACT ON SEAS/WINDS EACH DAY...CONDITIONS SHOULD GENERALLY REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS...ALTHOUGH NEAR SHORE WATERS SURROUNDING CAPE COD/ISLANDS MAY APPROACH 20-25 KT OUT OF THE SW. AN OCCASIONAL SHOWER OR THUNDERSTORM IS POSSIBLE WITH LOCALLY ROUGH CONDITIONS...BUT THIS THREAT SHOULD DROP BY TUE NIGHT. WED AND THU...MODERATE CONFIDENCE. WEAK HIGH PRES WILL BUILD OVER THE WATERS WITH WARMING CONDITIONS. EXPECT WINDS/SEAS TO REMAIN BELOW SCA CONDITIONS SAVE FOR MAYBE THU...WHERE INCREASING SW FLOW MAY LEAD TO 5 FT SWELLS MOVING UP THE COASTLINE AND IMPACTING THE SRN WATERS.
-- End Changed Discussion --
&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...SIPPRELL/GAF NEAR TERM...SIPPRELL SHORT TERM...SIPPRELL LONG TERM...GAF AVIATION...SIPPRELL/GAF MARINE...SIPPRELL/GAF

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.