Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
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
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 140736 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 336 AM EDT SUN SEP 14 2014 .SYNOPSIS...
-- Changed Discussion --
HIGH PRESSURE OVER THE GREAT LAKES BUILDS INTO NEW ENGLAND TODAY AND MONDAY...BRINGING DRY WEATHER ALONG WITH MILD AFTERNOONS AND CHILLY NIGHTS. A COLD FRONT WILL LIKELY BE ACCOMPANIED BY A PERIOD OF SHOWERS LATE MONDAY NIGHT INTO TUESDAY. MAINLY DRY BUT COOLER THAN NORMAL WEATHER FOLLOWS NEXT WEDNESDAY THROUGH FRIDAY. TEMPERATURES THEN LIKELY MODERATE TO NEAR NORMAL BY NEXT WEEKEND.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
330 AM UPDATE... COLD FRONT NOW OFFSHORE WITH NW WINDS ADVECTING IN DRY POST FRONTAL AIRMASS ACROSS THE REGION. HOWEVER SOME OF THE INTERIOR VALLEYS AND LOW LYING AREAS OF EASTERN MA /I.E. NORWOOD/ HAVE DECOUPLED AND RESIDUAL MOISTURE FROM LAST EVENINGS RAINS HAS RESULTED IN SOME PATCHY FOG. THIS INVERSION IS VERY SHALLOW AND WILL ERODE RAPIDLY WITH SUNRISE. THUS ANY PATCHY GROUND FOG WILL BE SHORT LIVED AND DISSIPATE SHORTLY AFTER SUNRISE. IN FACT WINDS WILL BRIEFLY BECOME BREEZY AFTER SUNRISE AS BLYR WARMS AND ERODES INVERSION RESULTING IN STRONGER WINDS ALOFT MIXING TO THE SURFACE. HOWEVER BY 15Z PGRAD RELAXES AND WINDS DIMINISH WITH AFTERNOON SEABREEZES POSSIBLE. POST FRONTAL AIRMASS IS SLIGHTLY COOLER THAN NORMAL WITH 925 MB TEMPS AROUND +10C...-1 STD FROM CLIMO. MODEL SOUNDINGS SUGGEST SUBSIDENCE INVERSION LIMITS MIXING TO ABOUT 900 MB. THIS WILL LIMIT HIGH TEMPS THIS AFTERNOON TO 65 TO 70...LOW 60S HIGHER TERRAIN. THIS IS ABOUT 5-8 DEGS COOLER THAN NORMAL. HOWEVER ABUNDANT SUNSHINE AND DIMINISHING WINDS WILL HELP OFFSET THE COOLER TEMPS...YIELDING A VERY PLEASANT DAY BY MID SEP STANDARDS.
-- End Changed Discussion --
&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
-- Changed Discussion --
TONIGHT...IDEAL RADIATIONAL COOLING WITH CLEAR SKIES...LIGHT WINDS AND A DRY ATMOSPHERE. GIVEN THESE CONDITIONS SIDED WITH THE COOLER MOS TEMPS COMPARED TO THE WARMER MODEL BLEND. MOST LOCATIONS DIP INTO THE 40S TONIGHT BUT AS COLD AS THE M30S OVER NORTHWEST MA AND SOUTHWEST NH. M30S APPEAR MORE WIDESPREAD IN SOUTHWEST NH SO HAVE ISSUED A FROST ADVISORY FOR CHESHIRE COUNTY. MONDAY...MORE OF THE SAME...CHILLY START TO THE DAY BUT SHORT WAVE RIDGING WILL PROVIDE MOSTLY SUNNY SKIES AND LIGHT WINDS WITH HIGH PRES OVERHEAD. TEMPS A FEW DEGS WARMER THAN TODAY WITH AFTERNOON HIGHS IN THE U60S TO L70S. LIGHT PGRAD SHOULD SUPPORT ANOTHER ROUND OF AFTERNOON SEABREEZES.
-- End Changed Discussion --
&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
-- Changed Discussion --
HIGHLIGHTS... *SHOWERS POSSIBLE FROM COLD FRONTAL PASSAGE MON NIGHT/TUE *BELOW NORMAL TEMPS OBSERVED AFTER LATE WEEK FRONTAL PASSAGE *LESS HUMIDITY AS DEW POINTS ARE BELOW 60F FOR THE ENTIRE PERIOD OVERVIEW... THIS PERIOD IS CHARACTERIZED BY A RIDGE IN THE WEST AND A TROUGH IN THE EAST OR THE TYPICAL POSITIVE PNA PATTERN AT LEAST TO START. WITH THE UPPER LEVEL LOW PRESSURE SYSTEM DROPPING SOUTH OUT OF CANADA...EXPECT THE ARCTIC OSCILLATION TO DROP MORE NEGATIVE. ALSO EXPECTING THE NAO TO DROP FROM POSITIVE TO MORE NEUTRAL INDICATING A SLOWING PATTERN. MODELS HANDLE THIS PERIOD FAIRLY WELL AND WITH ADEQUATE AGREEMENT ASIDE FROM THE HANDLING OF A SHORTWAVE THAT MOVES THROUGH THE REGION. THE 6Z GFS IS FASTER AND WEAKER WITH THE MOVEMENT OF THAT SHORTWAVE THROUGH THE REGION THAN THE ECMWF. THE LATTER HAS A STRONGER SHORTWAVE...WHICH FORMS A LOW PRESSURE SYSTEM SOUTH OF THE AREA. HAVE GONE WITH A BLEND OF THE MODELS TO ELIMINATE THE GFS BIAS TOWARDS QUICKER EVOLUTION THROUGH THE REGION AND THE HEAVIER PRECIPITATION FROM THE ECMWF. LATER IN THE PERIOD...A COLD FRONT PUSHES SOUTH THROUGH NEW ENGLAND WITH MORE MODEL DISAGREEMENT. THE ECMWF ALLOWS FOR A LATER PASSAGE OF THE FRONT LATE THURSDAY NIGHT WHILE THE GFS PUSHES IT THROUGH LATE WEDNESDAY/EARLY THURSDAY. FOLLOWING THE ENSEMBLES AND WPC...HAVE GONE WITH AN EARLY THURSDAY FRONTAL PASSAGE. DAILIES... TUESDAY...EVEN WITH THE SOUTHWEST WARMING WINDS...THE HUMIDITY REMAINS LOW WITH PWATS ONLY AROUND 1 INCH AND THE TOTAL OF TOTALS ONLY AROUND 40. FEEL A LOWER END EVENT MAY OCCUR FROM THIS WITH THE QUICK MOVING LOW PRESSURE SYSTEM. HAVE LEANED AWAY FROM THE ECMWF...BUT FEEL THE GFS MAY BE TOO LOW. ALSO DON/T SEE MUCH IN THE WAY OF INSTABILITY FOR THUNDER. WEDNESDAY THROUGH FRIDAY...AREAS OF HIGH PRESSURE PINWHEEL AROUND THE UPPER LEVEL LOW IN SOUTHEASTERN CANADA. A COLD FRONT LOOKS TO PASS THROUGH EARLY THURSDAY WITH TEMPERATURES AS COLD AS JUST OVER 2 SDS BELOW NORMAL AT 850MB OR 1.5 KM INTO THE SKY. AM EXPECTING A FEW CUMULUS CLOUDS TO BE AROUND...BUT NOT OVERCAST AT ALL. BEST CHANCE TO SEE THURSDAY OVERNIGHT TEMPS DIP BELOW 40F AND WOULD THEREFORE HAVE TO WATCH FOR FROST IN THOSE AREAS...NAMELY NORTHWESTERN MA AND SOUTHEASTERN NH. SATURDAY...THE 6Z GFS IS SHOWING A COLD FRONT...BUT WITH THE NAO BEGINNING TO GO NEGATIVE AND INDICATING A SLOWING PATTERN...WILL STICK WITH WHAT THE ECMWF AND OTHER ENSEMBLE MODELS ARE SHOWING AND ALLOW HIGH PRESSURE TO SLOWLY EXIT THE REGION.
-- End Changed Discussion --
&& .AVIATION /08Z SUNDAY THROUGH THURSDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. HIGH CONFIDENCE THRU MONDAY. TODAY...MVFR/IFR ACROSS RI/EASTERN MA AND SOUTHEAST NH WILL IMPROVE TO VFR BY 09Z. NNW WINDS MAY GUSTS UP TO 25 KT FROM 09Z TO 15Z THEN DIMINISH WITH AFTERNOON SEABREEZES POSSIBLE. TONIGHT...VFR ALONG WITH LIGHT WINDS. LOW RISK OF PATCHY MVFR INLAND IN FOG. MONDAY...VFR WITH LIGHT WINDS INTERIOR AND SEABREEZES ALONG THE COAST. KBOS TERMINAL...HIGH CONFIDENCE IN TAF EXCEPT FOR AFTERNOON WINDS. IFR/MVFR CONDITIONS IMPROVE TO VFR BY 09Z. SEABREEZE MAY DEVELOP THIS AFTERNOON BUT LOW CONFIDENCE. KBDL TERMINAL...HIGH CONFIDENCE IN TAF FOR VFR CONDITIONS. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY...HIGH CONFIDENCE. MONDAY NIGHT...VFR CONDITIONS EXPECTED. TUESDAY...SHOWERS BEGIN IN THE EARLY MORNING HOURS WITH MVFR CONDITIONS EXPECTED. THEN BECOMING VFR AS SHOWERS EXIT IN THE MID AFTERNOON HOURS. WEDNESDAY AND THURSDAY...VFR CONDITIONS EXPECTED. && .MARINE...
-- Changed Discussion --
FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. FORECAST CONFIDENCE IS HIGH THROUGH MONDAY. TODAY...NNW WINDS GUSTING UP TO 25 FROM ABOUT 5 AM TO 11 AM THEN DIMINISHING THEREAFTER. GOOD VSBY AS WELL. TONIGHT AND MONDAY...LIGHT WINDS AND GOOD VSBY. OUTLOOK...MONDAY NIGHT THROUGH THURSDAY... MONDAY NIGHT INTO TUE MORNING...MODERATE TO HIGH CONFIDENCE. HIGH PRESSURE NEARBY WILL RESULT IN A WEAK PRESSURE GRADIENT KEEPING WINDS/SEAS BELOW SCA THRESHOLDS. TUESDAY AFTERNOON INTO WEDNESDAY...MODERATE CONFIDENCE. SWELLS BEGIN TO BUILD TO BETWEEN 5 AND 7FT BEHIND THE DEPARTING LOW PRESSURE SYSTEM AND COLD FRONT. THIS IS ABOVE SCA LEVELS AND THEREFORE A SCA MAY BE NEED. THURSDAY...AS NEXT HIGH PRESSURE SYSTEM APPROACHES WITH WEAKER PRESSURE GRADIENT...EXPECT SWELLS TO DIE DOWN DURING THE DAY TO BELOW SCA THRESHOLD.
-- End Changed Discussion --
&& .BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR ANZ231- 232-251-255. SMALL CRAFT ADVISORY UNTIL 4 PM EDT THIS AFTERNOON FOR ANZ250- 254.
-- End Changed Discussion --
&& $$ SYNOPSIS...NOCERA/DUNTEN NEAR TERM...NOCERA SHORT TERM...NOCERA LONG TERM...99 AVIATION...NOCERA/99 MARINE...NOCERA/99

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