Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Text Only | 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 281805 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 205 PM EDT TUE JUL 28 2015 .SYNOPSIS... A TROUGH OF LOW PRESSURE ALOFT WILL BRING A RISK OF SCATTERED SHOWERS AND THUNDERSTORMS TO EASTERN MASSACHUSETTS AND POSSIBLY RHODE ISLAND TODAY. HOT AND HUMID CONDITIONS EXPECTED THROUGH THURSDAY. A COLD FRONT MAY BRING SCATTERED THUNDERSTORMS LATE THURSDAY AND THURSDAY NIGHT. WARM BUT DRIER AND LESS HUMID WEATHER IS EXPECTED FRIDAY INTO NEXT WEEKEND. && .NEAR TERM /UNTIL 7 PM THIS EVENING/...
-- Changed Discussion --
***A FEW STRONG TO SEVERE THUNDERSTORMS POSSIBLE THROUGH EARLY EVENING MAINLY ACROSS EASTERN MA AND RHODE ISLAND BUT CAN NOT RULE ONE OUT ACROSS THE INTERIOR WITH SOME TERRAIN INTERACTION*** 2 PM UPDATE... NO CHANGES MADE TO THE PREVIOUS FORECAST. LATEST SPC MESO-ANALYSIS SHOWS 2000 TO 3000 J/KG OF CAPE WITH EFFECTIVE BULK SHEAR OVER 50 KNOTS ACROSS EASTERN NEW ENGLAND. LATEST MESOSCALE MODELS INDICATE HIGHEST RISK FOR A FEW STRONG TO SEVERE THUNDERSTORMS ACROSS EASTERN NEW ENGLAND...ESPECIALLY SOUTHEAST MA AND INTO RHODE ISLAND. HOWEVER...CAN NOT COMPLETELY RULE ONE OUT ANYWHERE AS A RESULT OF SOME TERRAIN INTERACTION. WE ARE WATCHING ONE STRONG STORM RIGHT NOW IN NORTHWEST MA. PREVIOUS DISCUSSION FROM 1030 AM... OVERALL...A RATHER COMPLEX AND UNCERTAIN SETUP ON CONVECTIVE POTENTIAL THIS AFTERNOON INTO EARLY THIS EVENING. LOW CLOUDS HAVE BURNED OFF ACROSS MOST OF THE REGION BY LATE MORNING...EXCEPT FOR AREAS NEAR THE SOUTH COAST. EVEN IN THESE LOCATIONS...SHOULD SEE SKIES BECOME PARTLY TO MOSTLY SUNNY IN THE NEXT HOUR OR SO. STRONG EARLY MORNING SHORTWAVE THAT CROSSED NORTHERN NEW ENGLAND WAS MOVING AWAY FROM THE REGION. IN ITS WAKE...THERE WAS SOME SUBSIDENCE WHICH WILL AT LEAST ALLOW FOR A FAIR AMOUNT OF SUNSHINE FOR THE NEXT FEW HOURS. HIGH TEMPS WILL TOP OUT IN THE UPPER 80S TO NEAR 90 AND IT WILL BE HUMID WITH DEWPOINTS GENERALLY IN THE 60S. THE MAIN UNCERTAINTY CONTINUES TO REVOLVE AROUND CONVECTIVE POTENTIAL FROM MID AFTERNOON INTO EARLY THIS EVENING. WILL GO OVER BOTH THE FAVORABLE AND UNFAVORABLE INGREDIENTS FOR CONVECTION. 1) FAVORABLE: THE DEPARTING FIRST SHORTWAVE ACTUALLY HAS DELIVERED 500 MB TEMPS OF -12C TO EASTERN MA LATE THIS MORNING...WHICH IS QUITE COLD ALOFT CONSIDERING OUR AIRMASS AT THE SURFACE. THEREFORE...WE SHOULD HAVE NO PROBLEM ATTAINING 2000 TO 3000 J/KG OF CAPE ACROSS EASTERN NEW ENGLAND THIS AFTERNOON. QUITE HIGH FOR OUR NECK OF THE WOODS. AT THE SAME TIME...ANOTHER SHORTWAVE WILL BE DROPPING DOWN ALONG THE EASTERN MA COAST. IN ADDITION...0 TO 6 KM SHEAR VALUES WILL BE INCREASING ON THE ORDER OF 35 TO 45 KNOTS DURING THE AFTERNOON. 2)UNFAVORABLE: THE FIRST SHORTWAVE CREATED SUBSIDENCE AND WHILE IT WILL HELP TO ALLOW HIGH CAPE TO DEVELOP...DRY MID LEVEL AIR MAY ATTEMPT TO CUTOFF ANY UPDRAFTS. THIS IS PROBABLY ONE OF THE MAIN REASONS THAT SEVERAL MODELS ARE NOT SHOWING MUCH QPF. ALTHOUGH 0 TO 6 KM SHEAR IS QUITE IMPRESSIVE...LOW LEVEL WIND FIELDS ARE QUITE WEAK WHICH WILL BE ANOTHER LIMITING FACTOR. FINALLY...500 MB TEMPS ALONG THE EASTERN MA COAST WARM FROM -12C AROUND 18Z TO -9C BY 00Z. SO OVERALL...THERE ARE QUITE A BIT OF MIXED SIGNALS FROM MID AFTERNOON AND EVENING. WE DO THINK THAT THERE SHOULD AT LEAST BE ISOLATED TO SCATTERED THUNDERSTORMS DEVELOPING ACROSS EASTERN MA/RI WITH HELP FROM SOME CONVERGENCE ON THE SEA BREEZE FRONT. MANY HIGH RESOLUTION MODELS IN FACT SHOW THAT. HIT AND MISS ACTIVITY MAY EXTEND INTO CENTRAL MA WITH THE HELP OF THE TERRAIN. IN FACT...MAY EVEN SEE AN ISOLATED STORM OR TWO IN OUR FAR WESTERN ZONES ALTHOUGH PROBABLY FEW AND FAR BETWEEN. IF THOSE LIMITING FACTORS ARE OVERCOME...THERE IS THE POTENTIAL FOR A FEW STRONG TO SEVERE STORMS...GIVEN VERY HIGH CAPES AND RATHER COLD 500 MB TEMPS THROUGH 19 OR 20Z. BEST SHOT WILL BE ON THE SEA BREEZE FRONT BUT CAN/T RULE OUT SOMETHING ON THE HIGHER TERRAIN. AREAL COVERAGE OF ANY STORMS WILL PROBABLY BE LIMITED WITH DRY WEATHER DOMINATING...ESPECIALLY IN OUR WESTERN ZONES. IT COULD BE ONE OF THOSE SCENARIOS WHERE WE COULD END UP WITH JUST A FEW LOW TOPPED THUNDERSTORMS IF TOO MUCH DRY AIR ENTRAINS. HOWEVER...THERE ALSO IS A LOW RISK OF A VERY ISOLATED/LOCALIZED HIGH END SEVERE WEATHER EVENT IN THE FORM OF LARGE HAIL/MICROBURST GIVEN THE ABOVE REASONING.
-- End Changed Discussion --
&& .SHORT TERM /7 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... TONIGHT INTO TOMORROW... A FEW LINGERING SHOWERS ARE POSSIBLE AFTER 00Z. OTHERWISE EXPECT A QUIET NIGHT AS MID-LEVEL RIDGE BEGINS TO BUILD INTO THE REGION. WEAK FLOW AND INCREASING LOW LEVEL MOISTURE WILL ALLOW FOR ANOTHER ROUND OF FOG TO DEVELOP. ALTHOUGH BELIEVE THAT IT WONT BE AS WIDESPREAD AS TONIGHT. BEST CHANCE IS ACROSS THE CAPE AND ISLANDS AND WHERE PRECIP OCCURS TODAY. OVERNIGHT TEMPS WILL DROP INTO THE UPPER 60S TO LOW 70. HIGH PRESSURE BUILDS ACROSS SOUTHERN NEW ENGLAND TOMORROW BRINGING 18-19C 850MB TEMPS. THIS WILL ALLOW FOR TEMPS TO REACH IN THE LOW TO MID 90S. DEWPOINTS WILL STILL BE IN THE UPPER 60S TO LOW 70S LEADING TO HEAT INDEX VALUES IN THE MID 90S. CANNOT RULE OUT A SPOT SHOWER ON WEDNESDAY IF LOCATIONS REACH THEIR CONVECTIVE TEMPERATURES...ESP ACROSS THE HIGHER TERRAIN. BECAUSE OF THE UNCERTAINTY KEPT FORECAST DRY. && .LONG TERM /THURSDAY THROUGH MONDAY/... 350 AM UPDATE... HIGHLIGHTS... * VERY WARM AND HUMID THU * SCATTERED STORMS POSSIBLE LATE THU/THU NIGHT * DRIER/LESS HUMID FRI THRU MON BUT STILL WARM WED NIGHT/THU/THU NIGHT... GOOD MODEL AGREEMENT ON SHORT WAVE RIDGING OVER THE AREA WED NIGHT INTO THU. THUS DRY WEATHER TO START THIS PERIOD HOWEVER THE RISK OF SHOWERS/T-STORMS INCREASES LATE THU INTO THU NIGHT AS POTENT NORTHERN STREAM TROUGH CURRENTLY EXITING THE NORTHERN ROCKIES INTO THE HIGH PLAINS BEGINS TO APPROACH NEW ENGLAND FROM THE WEST. APPEARS TIMING OF THE FRONT COMES THROUGH OVERNIGHT...WELL AFTER PEAKING HEATING. THIS COMBINED WITH MARGINAL SHEAR KEEPS THE RISK LOW FOR STRONG CONVECTION LATE THU INTO THU NIGHT. HOWEVER GOOD SYNOPTIC SCALE LIFT WITH THIS TROUGH SUGGEST AT LEAST SHOWERS SHOULD BE ABLE TO HOLD TOGETHER AND MOVE ACROSS THE AREA LATE THU AND THU NIGHT. PWATS ABOVE NORMAL AND DEW PTS 65 TO 70 WILL INCREASE THE RISK FOR HEAVY DOWNPOURS. ALTHOUGH STILL 2 DAYS AWAY WILL NEED TO MONITOR LATER MODEL TRENDS. OTHERWISE VERY WARM AND HUMID CONDITIONS THU AHEAD OF APPROACHING COLD FRONT. A MODEL BLEND OFFERS HIGHS U80S TO L90S. FRIDAY THROUGH MONDAY... ANOMALOUS CLOSED LOW/VORTEX SETS UP OVER HUDSON/JAMES BAY THIS TIME PERIOD. THIS RESULTS IN BELOW NORMAL HEIGHTS AND MEAN TROUGH OVER THE GREAT LAKES INTO THE NORTHEAST. THIS WILL KEEP TEMPERATURES NEAR NORMAL /HIGHS MU80S/ AND LOWS IN THE 60S ALONG WITH TOLERABLE HUMIDITY AS DEW PTS AVERAGE IN THE 50S DURING THE DAYLIGHT HOURS. HOWEVER WITH THE NORTHERN STREAM JET SUPPRESSED SOUTHWARD INTO THE GREAT LAKES AND NORTHEAST THERE WILL BE THE RISK OF SCATTERED DIURNAL SHOWERS/T-STORMS JUST ABOUT EVERY DAY. TOO DIFFICULT AT THIS TIME RANGE TO TIME INDIVIDUAL SHORT WAVES. NOT A WASHOUT BUT THE RISK OF CONVECTION FROM TIME TO TIME. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
-- Changed Discussion --
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 CONDITIONS BUT HIT AND MISS SHOWERS/THUNDERSTORMS EXPECTED THROUGH EARLY EVENING WILL RESULT IN LOCALIZED LOWER CONDITIONS. ACTIVITY WILL BE ISOLATED...EXCEPT PERHAPS ACROSS EASTERN MA AND RHODE ISLAND WHERE SEA BREEZE CONVERGENCE MAY HELP. A FEW OF THE STORMS MAY BE STRONG TO EVEN SEVERE WITH HAIL AND GUSTY WINDS. HIGHEST RISK FOR THAT IS EASTERN MA/RI. TONIGHT...MODERATE CONFIDENCE. ANY ISOLATED TO SCATTERED CONVECTION SHOULD COME TO AN END EARLY THIS EVENING. OTHERWISE...VFR FOR MOST SITES EXCEPT FOR SOME PATCHY FOG IN THE TYPICALLY PRONE LOCATIONS. ALSO...CANNOT RULE OUT IFR IN STRATUS AND FOG ACROSS FAR SE MASS INCLUDING THE CAPE AND ISLANDS...BUT CONFIDENCE IN THAT IS LOW. WEDNESDAY...HIGH CONFIDENCE IN VFR CONDITIONS. KBOS TERMINAL...HIGH CONFIDENCE IN MAINLY VFR THROUGH TONIGHT. LOW CONFIDENCE ON WHETHER OR NOT A THUNDERSTORM IS IN THE VICINITY OF BOSTON BETWEEN 19Z AND 23Z. KBDL TERMINAL...HIGH CONFIDENCE IN MAINLY VFR THROUGH TONIGHT. OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/... 350 AM UPDATE... WED NGT/THU...PATCHY MVFR/IFR IN FOG WED NGT BUT QUICKLY IMPROVING TO VFR THU MORNING. LOW PROB THAT MVFR/IFR IN STRATUS LINGERS ALONG THE SOUTH COAST THU. THEN UNCERTAINTY ON HOW QUICK THIS FOG/STRATUS BURNS OFF SOUTH COAST. THU NIGHT...VFR-MVFR IN SCATTERED SHOWERS/T-STORMS. SOME UNCERTAINTY ON HOW WIDESPREAD PRECIP WILL BE. FRI AND SAT...VFR LIKELY. HIGH FORECAST CONFIDENCE.
-- End Changed Discussion --
&& .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH WEDNESDAY/...HIGH CONFIDENCE. WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS THROUGH WEDNESDAY. A FEW SPOT SHOWERS AND PERHAPS A THUNDERSTORM WILL BE POSSIBLE TODAY. THESE THUNDERSTORMS COULD CONTAIN GUSTY WINDS. SPECIAL MARINE WARNINGS MAY BE NEEDED WITH THE HIGHEST RISK ACROSS OUR WATERS ADJACENT TO EASTERN MA. OTHERWISE FOG AND STRATUS WILL BE THE ISSUE TONIGHT...WITH DRY WEATHER EXPECTED ON WEDNESDAY. OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/... 350 AM UPDATE... WED NIGHT AND THU...FAIRLY TRANQUIL WIND AND SEAS. POSSIBLE PATCHY FOG IN HUMID AIRMASS. THU NIGHT...MODEST SSW WIND AHEAD OF APPROACHING COLD FRONT. SCATTERED SHOWERS WITH EMBEDDED THUNDER POSSIBLE. FRI AND SAT...COLD FRONT SLOWLY MOVES OFFSHORE. ANOTHER WEAK FRONT MAY ENTER THE WATERS SAT. WSW WINDS EXPECTED. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/DUNTEN NEAR TERM...FRANK SHORT TERM...DUNTEN LONG TERM...NOCERA AVIATION...FRANK/DUNTEN MARINE...NOCERA/DUNTEN

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