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 022056 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 456 PM EDT TUE SEP 2 2014 .SYNOPSIS...
-- Changed Discussion --
A COLD FRONT WILL CROSS THE REGION TONIGHT AND WILL BE ACCOMPANIED BY SCATTERED SHOWERS AND THUNDERSTORMS. BEHIND THE FRONT DRIER AND MUCH LESS HUMID AIR OVERSPREADS THE AREA WEDNESDAY AND THURSDAY. HUMIDITY WILL ONCE AGAIN INCREASE BY THE END OF THE WEEK AS THE NEXT COLD FRONT BRINGS THE RISK FOR MORE SCATTERED SHOWERS/THUNDERSTORMS FRIDAY NIGHT AND SATURDAY. MORE AUTUMN-LIKE WEATHER FOLLOWS SUNDAY AND INTO AT LEAST EARLY NEXT WEEK WITH COOLER AND LESS HUMID CONDITIONS.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 4 PM UPDATE... SHOWERS AND THUNDERSTORMS FROM THE PRE-FRONTAL LIKE TROUGH WILL CONTINUE TO MOVE EASTWARD AND EVENTUALLY OFFSHORE OVER THE NEXT HOUR OR TWO. A FEW ISOLATED SHOWERS ARE POSSIBLE ACROSS THE INTERIOR...BUT WITH THE LACK OF DEEP MOISTURE THEY WILL STRUGGLE TO GROW LATE THIS AFTERNOON. INTERESTING NOTE...AFTER THE STORMS PASS MANY SITES DROP DOWN INTO THE MID-70F FOR TEMPS. BUT BECAUSE OF HOW JUICY AND TROPICAL THE AIRMASS IS THEY BOUNCE RIGHT BACK UP TO 90F WITHIN AN HOUR. ASIDE FROM A FEW ISO THUNDERSTORMS THIS AFTERNOON...EXPECT A MOSTLY QUIET EVENING BEFORE THE COLD FRONT APPROACHES LATER TONIGHT. TONIGHT... STRONG COLD FRONT WILL MOVE ACROSS THE NORTHEAST OVERNIGHT. THIS FRONT IS EXPECTED TO MOVE INTO THE WESTERN ZONES AROUND 02-04Z AND OFFSHORE BETWEEN 10-12Z. ANTICIPATE CONVECTION WILL BE ONGOING AS IT APPROACHES THE REGION PER THE AMOUNT OF SURFACE HEATING AND DYNAMICS OUT AHEAD OF IT IN WESTERN CWA`S. BY THE TIME IT APPROACHES THE REGION A GOOD AMOUNT OF INSTABILITY WILL BE LOSS SO WE MAY SEE DYING CONVECTION. HOWEVER SOME MODELS...ESP THE HIGH-RES GUIDANCE SHOWS ABOUT 500 J/KG OF CAPE LINGERING BY THE TIME THE FRONT APPROACHES. ON TOP OF THE POSSIBLE INSTABILITY...850MB LLJ DOES INCREASE AS THE FRONT APPROACHES AND SHEAR VALUES INCREASE AS WELL. IN FACT...GUIDANCE SHOWS THAT 0-6KM SHEAR INCREASES TO 25KTS...BUT IT IS THE 0-1 KM SHEAR THAT INCREASES TO 30-40KTS. LASTLY K-INDEX PLUME MOVES OVER THE REGION DURING THIS TIMEFRAME GIVING THE REGION THE MOISTURE IT NEEDS FOR THUNDERSTORMS TO CONTINUE. THEREFORE BELIEVE THAT ALL THE INGREDIENT MENTIONED ABOVE MAY ALLOW FOR A FEW STRONG TO PERHAPS A SEVERE STORM AS THE FRONT MOVES THE REGION. KEEP IN MIND THAT THIS IS AN OVERNIGHT EVENT WHICH IS NOT IN THE NORTHEAST FAVOR PER CLIMO...BUT CONDITIONS DO SHOW THAT A FEW STRONG STORMS ARE POSSIBLE. LASTLY...EVEN THOUGH THE REGION DID SEE SOME ACTION TODAY...THE ATMOSPHERE DID BOUNCE BACK VERY WELL AFTER THE STORMS PASSED. AS THE FRONT MOVES THROUGH THE K-INDEX VALUE AS WELL AS THE INSTABILITY DO DROP AFTER 06Z SO THAT THE CHANCE FOR ANY CONVECTION TO OCCUR DISSIPATES SIGNIFICANTLY. IN FACT...THE SHOWERS AND THUNDERSTORMS FROM THE FRONT WILL FRAGMENT AND BECOME VERY ISO IN NATURE BY THIS TIME FRAME AND MAY EVEN STRUGGLE TO REACH THE EAST COAST. WITH THE AMOUNT OF MOISTURE IN THE ATMOSPHERE BELIEVE THAT A FEW SHOWERS WILL REACH SO CONTINUED THE SLIGHT CHANCE POP FOR NOW. OVERNIGHT TEMPS WILL STRUGGLE TO DROP AS CLOUD COVER WILL KEEP TEMPS FROM RADIATING OUT OVERNIGHT AND DEWPOINTS WILL REMAIN IN THE 70S UNTIL FRONTAL PASSAGE. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... TOMORROW AND TOMORROW NIGHT... SURFACE FRONT WILL MOVE OFFSHORE BY EARLY TOMORROW MORNING AS UPPER LEVEL TROUGH WILL PUSH THROUGH AS WELL. 850 MB RIDGE WILL BEGIN TO SET UP OVER THE REGION ALLOWING FOR DRY AIR TO MOVE INTO THE AREA. THIS WILL KEEP THE WEATHER DRY FOR BOTH TOMORROW AND TOMORROW NIGHT. 850 MB TEMPS DROP DOWN TO -14C AND WITH MIXING UP TO 850MB WILL ALLOW FOR TEMPS TO REACH INTO THE MID TO UPPER 80S. DIFFERENCE WILL BE THE HUMIDITY AS DRY AIR WILL MIX DOWN DROPPING DEWS DOWN INTO THE UPPER 50S. WINDS WILL BE GUSTY REACHING ABOUT 20 MPH. OVERNIGHT...WITH CLEAR SKIES AND WINDS BECOME LIGHT AND VARIABLE...ANTICIPATE RADIATIONAL COOLING. LOWS WILL DROP INTO THE MID TO LOW 50S. A FEW SITES COULD EVEN DROP INTO THE UPPER 40S ACROSS CT VALLEY. && .LONG TERM /THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --
HIGHLIGHTS: * DRY THU/FRI WITH WARMER THAN NORMAL AFTERNOON TEMPS * MORE HUMID SAT WITH SCATTERED STORMS POSSIBLE * TREND TOWARD COOLER/LESS HUMID WEATHER SUN INTO EARLY NEXT WEEK THURSDAY AND FRIDAY... DRY/QUIET WEATHER CONTINUES THU WITH HIGH PRES AND A DRY/STABLE AIRMASS OVER THE REGION. IT WILL BE WARM WITH HIGHS OF 80- 85...COOLER ALONG THE COAST WITH AFTERNOON SEABREEZES...HOWEVER DEW PTS REMAINING IN THE 50S WILL PROVIDE COMFORTABLE HUMIDITY LEVELS. BY FRIDAY THE SUBTROPICAL RIDGE ALONG THE EAST COAST BRIEFLY BUILDS NORTHWARD INTO SOUTHERN NEW ENGLAND AHEAD OF THE NEXT NORTHERN STREAM TROUGH. THIS WILL RESULT IN WARMER TEMPS WITH HIGHS WELL INTO THE 80S COMBINED WITH MORE HUMID CONDITIONS AS DEW PTS CLIMB FROM THE 50S INTO THE 60S. THUS A WARM AND HUMID DAY FRIDAY. ALL MODEL GUIDANCE INCLUDING THE 12Z GEFS AND NEW 12Z ECMWF SUGGEST JET DYNAMICS/BEST SHEAR/INSTABILITY AND CONVERGENCE ASSOCIATED WITH COLD FRONT HOLD OFF UNTIL SAT. THUS SLIGHT CHANCE POPS CONFINED TO WESTERN NEW ENGLAND LATE FRI FROM A MODEL BLEND SEEMS REASONABLE. HENCE MOST OF THE AREA ESPECIALLY RI AND EASTERN MA MAY REMAIN DRY FRI. SATURDAY... ALL DETERMINISTIC AND PROBABILISTIC /12Z GEFS AND 12Z ECENS/ GUIDANCE SUGGEST COLD FRONT WILL MOVE SLOWLY INTO THE REGION SAT. TEMPS ARE PROJECTED TO BE IN THE 80S SAT ALONG WITH DEW PTS IN THE 60S TO NEAR 70 SO THIS SHOULD YIELD AT LEAST MARGINAL INSTABILITY. THE 12Z GEFS SUGGEST A 30-40% PROBABILITY OF UP TO 1200 J/KG OF CAPE. THIS COMBINED WITH MODEST JET DYNAMICS/SHEAR AND FRONTAL CONVERGENCE EXPECTING A RISK FOR SCATTERED THUNDERSTORMS ALONG WITH A THREAT FOR HEAVY RAIN AS PWATS CLIMB ABOVE NORMAL. COULD BE A FEW STRONG STORMS GIVEN THE PARAMETERS MENTIONED ABOVE. SUNDAY... LIKELY OUR TRANSITION DAY AS BOTH ENSEMBLES /12Z ECENS AND GEFS/ SUGGEST FRONT MAY BE SLOW TO CLEAR THE COAST SUN MORNING. THUS SHOWERS MAY LINGER EARLY SUNDAY ESPECIALLY SOUTH COAST WITH A TREND TOWARD DRIER WEATHER AS THE DAY PROGRESSES FROM NW TO SE. MONDAY AND TUESDAY... SHOULD BE DRIER...COOLER AND LESS HUMID AS FRONT MOVES OFFSHORE. HOWEVER SOME OF THE GUIDANCE SHOWS UNCERTAINTY HOW FAR OFFSHORE THIS BOUNDARY GETS. THUS CLOUDS AND POSSIBLE UNSETTLED WEATHER MAY LURK JUST OFFSHORE. WILL KEEP THE FORECAST DRY FOR NOW.
-- End Changed Discussion --
&& .AVIATION /21Z 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 WEDNESDAY NIGHT/...HIGH CONFIDENCE IN TRENDS. THROUGH 00Z...SCT TSRA NORTH OF THE PIKE WITH ISO TSRA SOUTH OF THE PIKE. ANTICIPATE BRIEF LOCALIZED LOWER CONDITIONS TIL ABOUT 22Z. TONIGHT...A LULL IN ACTIVITY AFTER 00Z. BEFORE ANOTHER ROUND OF SHOWERS WITH ISO THUNDER MOVES THROUGH AFTER 03/04Z. THIS CONVECTION IS ASSOCIATED WITH AN APPROACHING COLD FRONT WHICH WILL PASS THROUGH THE REGION OVERNIGHT. EXPECT CONVECTION TO WEAKEN AS IT MOVES THROUGH WITH BRIEF LOWERING IN CIG HEIGHTS. PATCHY FOG IS EXPECT AHEAD OF THE FRONT AND SHOULD DISSIPATE AS IT PASSES THROUGH. WED INTO WED NIGHT...VFR. PATCHY FOG IN CT VALLEY WED NIGHT. KBOS TERMINAL...HIGH CONFIDENCE IN TRENDS. MAY BE A SHOWER OR THUNDERSHOWER IN THE AFTERNOON. KBDL TERMINAL...HIGH CONFIDENCE. OUTLOOK...THURSDAY THROUGH SATURDAY... THU AND FRIDAY...HIGH CONFIDENCE. MAINLY VFR CONDITIONS OTHER THAN LATE NIGHT/EARLY MORNING PATCHY GROUND FOG IN THE TYPICALLY PRONE LOCATIONS. FRIDAY NIGHT AND SATURDAY...MODERATE CONFIDENCE. A PERIOD OF MVFR- IFR CONDITIONS EXPECTED IN LOW CLOUDS/FOG PATCHES AND SCT SHOWERS/THUNDERSTORMS. TIMING HIGHLY UNCERTAIN AT THIS POINT. SUNDAY...ANY MVFR ALONG SOUTH COAST SHOULD TREND TOWARD VFR WITH POTENTIAL SHOWERS MOVING OFFSHORE. OTHERWISE VFR PREVAILS ELSEWHERE.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. HIGH CONFIDENCE THROUGH THE PERIOD WEDNESDAY NIGHT. TONIGHT... SW FLOW BEGINS TONIGHT BEFORE A COLD FRONT PASSES OVER THE WATERS OVERNIGHT. EXPECT A FEW GUSTS TO AROUND 20 KT ARE POSSIBLE AS THE WINDS SHIFT TO THE W-NW. A FEW SHOWERS AND THUNDERSTORMS MAY MOVE OVER THE SOUTHERN WATERS BY MIDNIGHT LASTING TIL ABOUT 3AM. SEAS MAY APPROACH 5 FT ON THE SOUTH OCEAN WATERS BUT HAVE LOW CONFIDENCE AND HELD OFF ON ISSUING A SCA. OTHERWISE...SOME FOG MAY LEAD TO VSBY REDUCTIONS TONIGHT BEFORE THE FRONT PASSES. WED INTO WED NIGHT...QUIET BOATING WEATHER. A FEW GUSTS NEAR 15KTS POSSIBLE DURING THE DAY. OUTLOOK...THURSDAY THROUGH SATURDAY... MODERATE CONFIDENCE THROUGH THIS PERIOD. THURSDAY...HIGH CONFIDENCE. WEAK PRESSURE GRADIENT YIELDS LIGHT WINDS AND SEAS ALONG WITH GOOD VISIBILITIES SHOULD MAKE FOR NICE BOATING WEATHER. AFTERNOON SEABREEZES EXPECTED. FRIDAY...MODERATE TO HIGH CONFIDENCE. NEAR SHORE SOUTHWEST WIND GUSTS OF 20 TO 25 KNOTS MAY DEVELOP IN THE AFTERNOON WITH GOOD MIXING OVER THE LAND. SW WIND WAVES DEVELOP ESPECIALLY NEAR SHORE. DRY WEATHER WILL PREVAIL WITH A CHANCE OF SHOWERS/T-STORMS INCREASING AFTER SUNSET. FRIDAY NIGHT AND SATURDAY...MODERATE CONFIDENCE. AREAS OF FOG MAY AFFECT THE SOUTHERN WATERS. SOUTHWEST WIND GUSTS AROUND 20 KNOTS ARE EXPECTED AHEAD OF AN APPROACHING COLD FRONT. THERE WILL BE THE RISK OF SCT SHOWERS AND THUNDERSTORMS DURING THE DAY SATURDAY WITH A FEW STRONG STORMS POSSIBLE...WIND AND HEAVY RAIN. SUNDAY...FRONT BEGINS TO MOVE OFFSHORE SLOWLY BUT SHOWERS MAY LINGER ESPECIALLY IN THE MORNING.
-- End Changed Discussion --
&& .CLIMATE... BOSTON LOGAN AIRPORT REACHED 93 DEGREES TODAY. THIS IS THE WARMEST TEMPERATURE IN BOSTON SO FAR THIS SUMMER. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/DUNTEN NEAR TERM...DUNTEN SHORT TERM...DUNTEN LONG TERM...NOCERA AVIATION...NOCERA/DUNTEN MARINE...NOCERA/DUNTEN CLIMATE...DUNTEN

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