Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 130756 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 356 AM EDT SAT SEP 13 2014 .SYNOPSIS... HIGH PRESSURE DOMINATES OVERNIGHT. A QUICK MOVING WEATHER SYSTEM WILL BRING SCATTERED SHOWERS TO THE AREA LATE SATURDAY AFTERNOON AND EARLY EVENING. HIGH PRESSURE BRINGS DRY WEATHER WITH SLIGHTLY BELOW NORMAL TEMPERATURES SUNDAY INTO MONDAY. THE NEXT COLD FRONT WILL LIKELY BRING A PERIOD OF SHOWERS LATE MONDAY NIGHT INTO TUESDAY. MAINLY DRY WEATHER EXPECTED NEXT WEDNESDAY THROUGH FRIDAY WITH SLIGHTLY BELOW NORMAL TEMPERATURES CONTINUING. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... 130 AM UPDATE... ADJUSTED SKY COVER GRIDS BASED ON LATEST OBSERVATIONS AND SATELLITE PICTURES. RAP SEEMS TO HAVE BEST HANDLE ON PATCHES OF STRATOCUMULUS. ADJUSTED TEMPERATURES STILL A LITTLE COOLER IN SE ZONES BASED ON LATEST OBSERVED TRENDS. 1015 PM UPDATE... QUIET NIGHT WITH LITTLE CHANGE NEEDED IN FORECAST. DID LOWER HOURLY AND MIN TEMPS FOR PORTIONS OF SE MA AND MARTHAS VINEYARD TO ACCOUNT FOR CURRENT TRENDS AND CLIMATOLOGY. KEPT POP NEAR ZERO PERCENT THROUGH 8 AM AND JUST MADE A FEW TWEAKS WITH THE SKY COVER TO BE CONSISTENT WITH CURRENT TRENDS. 630 PM UPDATE... STRATO-CUMULUS CLOUDS HAVE DISSIPATED EARLY THIS EVENING ACROSS THE CAPE AND ISLANDS. OTHERWISE...MAINLY CLEAR SKIES WERE IN PLACE EARLY THIS EVENING OTHER THAN A TOUCH OF HIGH CLOUDINESS. IDEAL SEP WEATHER ACROSS THE REGION THROUGH THE EVENING WITH MAINLY CLEAR SKIES...COMFORTABLE TEMPS AND LIGHT WINDS. AFTER SUNSET...TEMPS WILL FALL FAIRLY QUICKLY GIVEN DRY ATMOSPHERE...CLEAR SKIES AND LIGHT WINDS. MANY LOCATIONS WILL DIP INTO THE MU40S TONIGHT INCLUDING PLACES SUCH AS MARTHAS VINEYARD... NORWOOD AND OTHER INTERIOR EASTERN MA LOCATIONS. ALSO WESTERN MA AND SOUTHWEST NH SHOULD FALL INTO THE MU40S. ELSEWHERE MINS WILL BE IN THE LOW TO MID 50S. TRICKY PART TO THE FORECAST WILL BE IF SOME LOW CLOUDS ARE ABLE TO DEVELOP NEAR THE COAST TOWARD DAYBREAK. THESE CLOUDS MAY REAPPEAR TOWARD SUNRISE GIVEN BLYR COOLING OVERNIGHT. THUS COULD SEE SKIES BECOME PARTLY TO MOSTLY CLOUDY TOWARD DAYBREAK OVER EASTERN MA AND POSSIBLY INTO RI...BUT CONFIDENCE IS LOW. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... SATURDAY... DRY TO START THE DAY BUT QUICK MOVING NORTHERN STREAM SHORT WAVE TROUGH APPROACHES FROM THE WEST. TWO AREAS OF SHOWERS WILL TRACK ACROSS THE NORTHEAST. FIRST BATCH WILL BE OVER NY STATE AND NORTHERN NEW ENGLAND WITH PARENT LOW AND ACCOMPANYING LOW TO MID LEVEL JET. A SECOND AREA OF SHOWERS WILL TRACK SOUTH OF NEW ENGLAND AS LAST NIGHT/S FRONTAL BOUNDARY LIFTS NORTHWARD WITH SECONDARY LOW PRES DEVELOPING ON THE FRONT IN RESPONSE TO RRQ OF THE UPPER JET STREAK. THIS YIELDS LIKELY POPS ACROSS CAPE COD AND THE ISLANDS WITH CHANCE POPS ELSEWHERE FOR SCATTERED SHOWERS. GREATEST RISK OF SHOWERS IS SOMEWHERE BETWEEN 4-8 PM. COULD BE SOME HEAVIER SHOWERS ALONG SOUTH COAST AND OFFSHORE AS PWATS CLIMB TO 2 INCHES /+2 STD FROM CLIMO/. HOWEVER INSTABILITY ALOFT AND AT THE SURFACE IS LACKING SO HEAVIER SHOWERS AND THUNDER MAY BE WELL OFFSHORE. SYSTEM IS VERY PROGRESSIVE SO NOT EXPECTING A SOAKING RAIN. IN FACT SOME LOCATIONS MAY ONLY SEE A TRACE OF RAINFALL WITH OTHER LOCATIONS SUCH AS WELL INLAND AND ALONG THE SOUTH COAST PERHAPS A TENTH OR TWO. TEMPS A FEW DEGS COOLER THAN TODAY GIVEN THE COOLER START ALONG WITH INCREASING CLOUDS AND LIGHT ONSHORE WINDS. SATURDAY NIGHT... QUICK MOVING SYSTEM EXITS THE REGION BETWEEN 00Z WEST TO PERHAPS 03Z CAPE COD. EXPECT DECREASING CLOUDS AND DRIER AIR TO OVERSPREAD THE REGION. NORTHERLY WINDS WILL BECOME GUSTY LATE AT NIGHT AND TOWARD SUNRISE SUNDAY WITH A FEW GUSTS UP TO 25 MPH POSSIBLE. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... HIGHLIGHTS... * LOW RISK OF PATCHY FROST SUN NIGHT ACROSS DISTANT INTERIOR * A PERIOD OF SHOWERS LIKELY LATE MON NIGHT/TUE * DRY WEATHER/SLIGHTLY BELOW NORMAL TEMPS NEXT WED-FRI OVERVIEW... OVERALL MODEL GUIDANCE IS IN AGREEMENT WITH A BROAD TROUGH OVER THE EASTERN HALF OF THE CONTINENT AND A FULL-LATITUDE RIDGE OVER WESTERN NORTH AMERICA. IN FACT APPEARS THAT THE NORTHERN BRANCH OF THE JET STREAM REMAINS FAIRLY PROGRESSIVE ESP SINCE THE NAO TRENDING MORE POSITIVE FOR THE FIRST HALF OF THIS FORECAST. THE FLOW DOES BEGIN TO BECOME MORE AMPLIFIED TOWARDS THE END OF THE PERIOD AS A TROUGH DIGS OVER THE EASTERN PACIFIC LEADING TO A RIDGE IN THE CENTRAL CONUS....ABOUT WHEN THE NAO BECOMES MORE NEUTRAL. HOWEVER IT LOOKS LIKE THE EASTERN CONUS WILL STILL REMAIN IN A TROUGH PATTERN THROUGH THE WORK WEEK WITH A POSSIBLE CHANGE IN THE PATTERN BY NEXT WEEKEND. ONLY MAJOR WEATHER MAKE TO WATCH FOR AT THE MOMENT IS THE SHORTWAVE PASSING THROUGH MONDAY NIGHT/TUESDAY BRINGING SHOWERS TO THE REGION. LOW CONFIDENCE ON EXACT TIMING BUT CONFIDENCE IS INCREASING THAT PRECIP WILL OCCUR. OTHERWISE HIGH PRESSURE WILL PREVAIL WITH TEMPS AT OR BELOW AVERAGE FOR THIS TIME OF YEAR. IN FACT SUNDAY NIGHT AND MID TO LATE NEXT WEEK MAY NEED TO WATCH FOR FROST HEADLINES. DETAILS... MONDAY... A MODIFIED CANADIAN HIGH WILL BUILD INTO NEW ENGLAND DURING THIS PORTION OF THE FORECAST...CRESTING OVER THE REGION ON MONDAY. LOWS ON SUN NIGHT WILL BE QUITE CHILLY FOR SEPTEMBER. ALTHOUGH RECORD COLD IS NOT EXPECTED...WE MAY STILL SEE SOME MIDDLE TO UPPER 30S ACROSS PORTIONS OF SOUTHWEST NH/NORTHWEST MA...WHERE THIS IS A LOW RISK FOR SOME PATCHY FROST IN THE TYPICALLY COOLEST OUTLYING LOCATIONS. FOR MONDAY HIGHS...EVEN WITH FULL SUNSHINE TEMPS WILL ONLY REACH INTO THE MID 60S TO LOWER 70S...SINCE THE SUN ANGLE IS LOW. DRY WEATHER WILL PREVAIL. MONDAY NIGHT INTO TUESDAY... THE NEXT SHOT FOR ANY SHOWERS WILL BE LATE MONDAY NIGHT INTO TUESDAY AS ANOTHER SHORTWAVE MOVES THROUGH THE FLOW. OVERALL GUIDANCE HAS TRENDED TO BE ON THE WETTER SIDE SO CONFIDENCE IS INCREASING THAT PRECIP WILL OCCUR. RIGHT NOW LOOKS AS IF DROUGHT STRICKEN RI AND SE MASS HAVE THE BETTER SHOT FOR THE HIGHER QPF AMOUNTS. ALTHOUGH THE EC DOES HAVE A QPF BULLS-EYE FOR THE REGION...NOTICED THAT THE GFS HAS TICKED UP SO OVER 0.25 TO 0.5 INCHES IS NOT OUT OF THE QUESTION...ESPECIALLY SINCE PWAT VALUES DO NOSE IN AT ABOUT 1.5 INCHES. INSTABILITY LOOKS FAIRLY LIMITED...SO WILL NOT INCLUDE THUNDER IN THE FORECAST AT THIS TIME. HIGHS SHOULD BE IN THE 60S TO AROUND 70. END OF THE WORK WEEK... HIGH PRESSURE FROM CANADA WILL SET UP OVER THE NORTHEAST ON WED INTO FRIDAY. THE GFS BRING AN ARCTIC FRONT ACROSS THE REGION ON WED WHILE THE EC HOLDS IT UP UNTIL THURSDAY NIGHT. EITHER WAY GUIDANCE IS SHOWING 850 MB TEMPS DROPPING BELOW 0C. THIS WILL KEEP TEMPS WELL BELOW AVERAGE...IN THE 60S RESULTING IN CRISP FALL LIKE TEMPS. BECAUSE OF THE DIFFERENCE...WILL CONTINUE WITH A BLEND OF PREV FORECAST AS WELL AS THE ENSEMBLES FOR NOW. EITHER WHICH WAY WE MAY NEED TO BEGIN TO WATCH FOR THE RISK FOR SOME FROST IN SOUTHWEST NH/NORTHWEST MA...WHERE WINDS CAN DECOUPLE. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. OVERNIGHT... MODERATE CONFIDENCE. MAIN CHALLENGE ARE A FEW PATCHES OF STRATOCUMULUS CLOUDS IN 30-35 HUNDRED LAYER. RAP MODEL SEEMS TO HAVE BEST HANDLE SO FAR ON THIS. LIGHT NORTH TO NORTHEAST WINDS EXPECTED TO BECOME MORE FROM THE EAST TO NORTHEAST AFTER DAYBREAK. SATURDAY... MVFR CIGS EXPECTED TO DEVELOP FROM WEST TO EAST AND SOUTH TO NORTH DURING THE AFTERNOON. SCATTERED SHOWERS MOST LIKELY AFTER 20Z WITH SOME MOVING FROM WEST TO EAST AND A SECOND AREA SOUTHWEST TO NORTHEAST TOWARD THE CAPE AND ISLANDS. SAT NIGHT... MVFR CIGS IN SCATTERED SHOWERS WITH PATCHES OF IFR CIGS POSSIBLE SE COASTAL AREAS. CONDITIONS IMPROVING TO VFR BY 03Z WEST AND BY 06Z EAST. MODEST NNE WIND DEVELOPS 06Z- 12Z WITH GUSTS UP TO 20-25 KT POSSIBLE E COASTAL AREAS. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. CIGS BKN030 POSSIBLE A FEW HOURS ON EITHER SIDE OF SUNRISE...THEN PROBABLY A PERIOD OF VFR MID TO LATE MORNING BEFORE CIGS LOWERING TO MVFR RANGE BY MID OR LATE AFTERNOON. SCATTERED SHOWERS MAY LOWER VSBYS TO MVFR THRESHOLDS FOR A TIME LATE AFTERNOON/EARLY EVENING. GREATEST RISK OF SHOWERS 20Z SAT THRU 03Z SUN. CONDITIONS IMPROVING AFTER 03Z SUN. KBDL TERMINAL...MODERATE TO HIGH CONFIDENCE. GREATEST RISK OF SHOWERS 18Z SAT THRU 00Z SUNDAY WITH A PERIOD OR TWO OF MVFR CIGS AND VSBYS POSSIBLE. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY...HIGH CONFIDENCE. MAINLY VFR CONDITIONS OVER THIS TIME...EXCEPT FOR A PERIOD OF MVFR- IFR CONDITIONS LATE MON NIGHT/TUE IN A ROUND OF SHOWERS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. FORECAST CONFIDENCE IS MODERATE TO HIGH THROUGH SUNDAY. OVERNIGHT...LIGHT EAST TO NORTHEAST WINDS...DRY WEATHER AND GOOD VSBY. SATURDAY...GENERALLY LIGHT EASTERLY WINDS. ONE AREA OF LOW PRES TRACKS NE INTO NY STATE AND ANOTHER WEAK LOW FORMS OFF THE NJ COAST. CHANCE OF SHOWERS LATE IN THE DAY WITH A LOW RISK OF THUNDER WELL SOUTH OF NEW ENGLAND. SAT NIGHT...WEAK LOW PRES MOVES NE ACROSS GEORGES BANK. A MODEST NORTH WIND DEVELOPS WITH A CHANCE OF GUSTS TO NEAR 25 KT LATE. SCATTERED SHOWERS DURING THE EVENING GIVES WAY TO DRY WEATHER AND GOOD VSBY. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY.... MONDAY 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. MAY SEE SOME MARGINAL SCA WINDS/SEAS ACROSS THE OUTER-WATERS BEHIND A COLD FRONT/LOW PRESSURE SYSTEM IN THE COOL AIR ADVECTION PATTERN. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/DUNTEN NEAR TERM...FRANK/NOCERA/THOMPSON SHORT TERM...NOCERA LONG TERM...DUNTEN AVIATION...NOCERA/DUNTEN/THOMPSON MARINE...NOCERA/DUNTEN/THOMPSON

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