Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 180131 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 931 PM EDT WED SEP 17 2014 .SYNOPSIS... HIGH PRESSURE WILL KEEP CONDITIONS COOL AND DRY TONIGHT. A WEAK COLD FRONT WILL CROSS THE AREA ON THURSDAY...BUT MOISTURE ASSOCIATED WITH THE FRONT IS LIMITED. COLD HIGH PRESSURE BUILDS INTO THE AREA DURING THURSDAY NIGHT AND FRIDAY. SOME FROST IS POSSIBLE EARLY FRIDAY MORNING IN SOME AREAS. THE HIGH WILL THEN SLIP OFFSHORE AND SOUTHWEST FLOW BEHIND IT WILL ALLOW TEMPERATURES TO WARM TO NEAR OR ABOVE NORMAL SUNDAY AND MONDAY. A COLD FRONT MOVES THROUGH ON MONDAY...FOLLOWED BY COOLER WEATHER TUESDAY AND WEDNESDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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930 PM UPDATE... WEAK COLD FRONT WAS DROPPING SE FROM ST LAWRENCE VALLEY AND WILL BRING SOME PATCHY CLOUDS INTO WESTERN NEW ENGLAND OVERNIGHT. OTHERWISE CLEAR SKIES EXPECTED. LIGHT OR CALM WINDS WILL ALLOW FOR GOOD RADIATIONAL COOLING OVERNIGHT. LOWS WILL DROP WELL DOWN INTO 40S ACROSS INTERIOR AND IN USUAL COLD SPOTS CLOSER TO COAST INCLUDING MARTHAS VINEYARD AIRPORT...NORWOOD AND TAUNTON. PATCHY VALLEY FOG ALSO APPEARS LIKELY.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... THURSDAY... THE COLD FRONT WILL MOVE THROUGH SOUTHERN NEW ENGLAND DURING THE DAY...WITH WINDS SHIFTING TO THE NORTHWEST. MODELS CONTINUE TO SHOW MINIMAL MOISTURE ASSOCIATED WITH THIS FRONT AS IT CROSSES THROUGH OUR AREA. WILL LIKELY SEE INCREASING CLOUDS WITH DIURNAL CUMULUS...CAN/T RULE OUT AN ISOLATED SHOWER OR TWO BUT WITH PRECIPITABLE WATER UNDER AN INCH ANY RAIN AMOUNT WOULD BE LIGHT AND LIKELY BRIEF. MAIN CONCERN WITH THE FRONT WILL BE USHERING IN COOLER TEMPERATURES. THURSDAY NIGHT... POTENTIAL FOR THE COOLEST PORTION OF THE FORECAST. WITH THE COLD FRONT SOUTHEAST OF THE AREA...CLEARING IS EXPECTED IN THE EVENING...WITH COLD HIGH PRES BUILDING OVER THE AREA. DEWPOINTS SHOULD FALL INTO THE 30S...SO ASSUMING CLEARING OCCURS QUICKLY ENOUGH WITH RADIATIONAL COOLING...TEMPS COULD FALL INTO THE MID 30S IN NW MA/SW NH VALLEYS WHICH MAY REQUIRE FROST ADVISORIES. ELSEWHERE...STILL A COOL MORNING FRI...UPPER 30S AND LOW 40S POSSIBLE. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... BIG PICTURE... ZONAL FLOW FRIDAY WITH 500 MB HEIGHTS BUILDING FROM A LITTLE BELOW NORMAL TO A LITTLE ABOVE BY THE NIGHTTIME. UPPER RIDGE BUILDS OVER THE WESTERN STATES WHILE A SHORTWAVE IN THE FLOW DIGS OVER THE NORTHERN PLAINS AND GREAT LAKES OVER THE WEEKEND. THE TROUGH THEN MOVES OVER NEW ENGLAND EARLY NEXT WEEK. BEST CHANCE OF SHOWERS WOULD BE SUNDAY NIGHT-MONDAY AS THE TROUGH APPROACHES. EXPECT A WARMING TREND OVER THE WEEKEND FOLLOWED BY COOLING TEMPS EARLY NEXT WEEK AS THE TROUGH MOVES OVERHEAD. THE DAILIES... FRIDAY-SATURDAY-SUNDAY... HIGH PRESSURE CENTERED OVER NORTHERN NEW ENGLAND FRIDAY MOVES EAST OVER THE MARITIMES DURING THE WEEKEND. THE RIDGE AXIS HOLDS ACROSS SOUTHERN NEW ENGLAND INTO SATURDAY...THEN SHIFTS SOUTH SUNDAY. THIS SHOULD SUPPORT DRY WEATHER THROUGH THE PERIOD. THE ECMWF ACTUALLY BRINGS SHOWERS INTO OUR NORTHWEST AREAS SATURDAY NIGHT AND THEN AGAIN SUNDAY AFTERNOON. BUT BOTH GFS AND ECMWF SHOW A SIMILAR JET POSITION ENTERING THE ST LAWRENCE VALLEY...AND THE GFS IS DRY UNTIL SUNDAY NIGHT. ADDED TO THIS IS THE OVERALL DRY PATTERN FOR SOUTHERN NEW ENGLAND THE PAST FEW WEEKS AND WHICH FAVORS THE DRIER FORECAST. TEMPS AT THE TOP OF THE MIXED LAYER ARE FORECAST EQUIV TO A TEMP OF 0-1C AT 850 MB FRIDAY...WARMING TO 10-11C BY SUNDAY. THIS SUPPORTS MAX SFC TEMPS UPPER 50S-LOWER 60S FRIDAY...WARMING TO 75-80 SUNDAY. WINDS IN THE MIXED LAYER ARE FORECAST TO REACH NEAR 20 KNOTS SATURDAY AND 25 KNOTS SUNDAY. WE HAVE BUMPED UP THE MODEL GRIDS TO REFLECT THESE VALUES. SUNDAY NIGHT-MONDAY... UPPER SHORTWAVE MOVES INTO THE GREAT LAKES AND SWINGS A COLD FRONT THROUGH SOUTHERN NEW ENGLAND LATE SUNDAY NIGHT OR MONDAY MORNING. THE ECMWF IS A LITTLE FASTER WITH FROPA...BUT WE STAYED CLOSER TO THE GFS. MUCH OF THE SYSTEM REMAINS TO OUR NORTH BUT SOUTHERN NEW ENGLAND REMAINS IN THE RIGHT ENTRANCE REGION OF THE SUPPORTING UPPER JET WHICH SHOULD PROMOTE SOME LIFT. WE WILL HOLD WITH CHANCE POPS FOR SHOWERS OVERNIGHT AND MONDAY. TUESDAY-WEDNESDAY... UPPER TROUGH AND COLD POOL MOVE OVERHEAD TUESDAY AND EAST OF US WEDNESDAY. SURFACE HIGH PRESSURE BUILDS IN BOTH DAYS. ENOUGH DESTABILIZING ALOFT AND CLOUD-LEVEL MOISTURE TO SUPPORT DIURNAL CLOUDS TUESDAY. OTHERWISE FAIR WEATHER BOTH DAYS. TEMPS IN THE MIXED LAYER SUPPORT MAX SFC TEMPS IN THE 60S BOTH DAYS. DEW POINTS IN THE UPPER 30S AND 40S WILL SUPPORT MIN SFC TEMPS IN THE 40S...POSSIBLY SOME UPPER 30S. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH THURSDAY NIGHT/...HIGH CONFIDENCE. TONIGHT AND THURSDAY...HIGH CONFIDENCE. VFR CONDITIONS EXPECTED ACROSS THE AREA. SCATTERED AREAS OF IFR CIGS/VSBYS IN PATCHY FOG/STRATUS LATE TONIGHT OVER THE FAR INTERIOR. VERY ISOLATED SHOWERS POSSIBLE DURING THURSDAY...ANY RAIN SHOULD BE LIGHT WITH PROBABLE VFR CONDITIONS WITH THE LIGHT SHOWERS. THURSDAY NIGHT...HIGH CONFIDENCE. VFR CONDITIONS EXPECTED. KBOS TERMINAL...HIGH CONFIDENCE IN TAF TONIGHT WITH VFR CONDITIONS THRU WED. MODERATE CONFIDENCE IN NW WINDS ON WED BECOMING E/NE DURING THE PM. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...FRIDAY THROUGH MONDAY...MODERATE TO HIGH CONFIDENCE. VFR THROUGH THE PERIOD. PATCHY IFR CIGS/VSBYS IN FOG SATURDAY AND SUNDAY EARLY MORNINGS. PATCHY MVFR IN SHOWERS SUNDAY NIGHT AND MONDAY. SOUTHWEST WINDS SATURDAY MAY GUST TO 20 KNOTS. SOUTHWEST WINDS SUNDAY MAY GUST 25 KNOTS...POSSIBLY A LITTLE HIGHER. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH THURSDAY NIGHT/...MODERATE CONFIDENCE. TONIGHT AND THURSDAY... SWELL FROM HURRICANE EDOUARD WILL SLOWLY BUILD INTO THE COASTAL WATERS WITH INCREASING SEAS. THERE IS A POSSIBILITY THAT SEAS MAY APPROACH 5 FEET ON THE OUTER COASTAL WATERS FOR A FEW HOURS THURSDAY MORNING. HOWEVER...CONFIDENCE IN THIS NOT HIGH ENOUGH AT THIS TIME TO POST HEADLINES. THURSDAY NIGHT...THE POTENTIAL EXISTS FOR 5 FOOT SEAS ON THE OUTER COASTAL WATERS THURSDAY NIGHT...AND WITH COLD AIR ADVECTION BEHIND THE COLD FRONT THURSDAY NIGHT SOME GUSTS IN THE LOW 20 KT RANGE ARE POSSIBLE ON THE OUTER COASTAL WATERS AS WELL. SMALL CRAFT ADVISORIES MAY BE NEEDED FOR SEAS STARTING THURSDAY NIGHT. OUTLOOK...FRIDAY THROUGH MONDAY...MODERATE CONFIDENCE. FRIDAY...DIMINISHING NORTHEAST TO EAST WIND LESS THAN 20 KNOTS. THERE WILL BE SOME 5 FOOT SEAS ON THE EASTERN WATERS FRIDAY MORNING SUPPORTED BY A 2-3 FOOT SOUTHEAST SWELL...BUT THIS WILL SUBSIDE THROUGH THE DAY. SMALL CRAFT ADVISORY FOR SEAS MAY BE NEEDED FOR PART OF FRIDAY. SATURDAY-SUNDAY...WINDS SWING AROUND TO SOUTHWEST WITH DAYTIME GUSTS AROUND 20 KNOTS...POSSIBLY NEAR 25 KNOTS SUNDAY. SEAS WILL REMAIN 2-4 FEET. A COLD FRONT APPROACHES LATE SUNDAY WITH A CHANCE OF SHOWERS SUNDAY NIGHT. MONDAY... A COLD FRONT CROSSES THE WATERS EARLY IN THE DAY. WEST WINDS BEHIND THE FRONT WILL REMAIN LESS THAN 20 KNOTS. SEAS WILL BUILD TO 5-7 FEET ON THE OUTER AND EXPOSED WATERS...AS A SOUTH SWELL INCREASES TO 3-5 FEET. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/NMB NEAR TERM...JWD SHORT TERM...NMB LONG TERM...WTB AVIATION...WTB/NMB MARINE...WTB/NMB

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