Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 031405 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1005 AM EDT THU SEP 3 2015 .SYNOPSIS... A COLD FRONT WILL SWEEP ACROSS NEW ENGLAND TODAY AND WILL BE ACCOMPANIED BY SCATTERED AFTERNOON/EVENING SHOWERS AND THUNDERSTORMS. CANADIAN HIGH PRESSURE BUILDS OVER NEW ENGLAND FRIDAY AND INTO THE LABOR DAY WEEKEND. THE HIGH MOVES JUST OFFSHORE EARLY NEXT WEEK YIELDING MAINLY DRY BUT WARMER THAN NORMAL TEMPERATURES. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... 10 AM UPDATE... FORECAST LOOKS ON TRACK THIS MORNING...ONLY EXCEPTION IS THE PATCH OF MARINE STRATUS/FOG DRIFTING EASTWARD FROM LONG ISLAND AND VICINITY TOWARDS BLOCK ISLAND. HAVE ADDED SOME CLOUD COVER AND PATCHY FOG TO THE VICINITY OF BLOCK ISLAND THRU MIDDAY...THIS MARINE CLOUD BANK SHOULD CONTINUE TO MIX/LIFT OVER THE NEXT COUPLE OF HOURS. OTHERWISE...PATCHY FOG OVER THE INTERIOR CONTINUES TO LIFT AND DISSIPATE...THEN EXPECTING DIURNAL CUMULUS CLOUDS WITH SCATTERED/ISOLATED SHOWERS/T-STORMS THIS AFTERNOON. PREVIOUS DISCUSSION FOLLOWS... =================================================================== LEFTOVER UPPER LVL CI DEBRIS FROM EARLY CONVECTION CONTINUES TO SPILL ACROSS THE NRN TIER OF SRN NEW ENGLAND THIS MORNING. OTHERWISE...CLEAR SKIES AND CALM CONDITIONS PREVAIL. THESE CLOUDS MAY LIMIT SOMEWHAT THE RISK FOR EARLY MORNING FOG IN SPITE OF THE DWPTS IN THE LOW-MID 60S. HOWEVER...SOME AREAS ALREADY REPORTING MODEST FOG IN THE VALLEYS OF WRN CT/MA. BACKDOOR COLD FRONT WILL BE SLIDING INTO THE REGION THROUGH THE DAY TODAY...STALLING AS IT MEETS THE MORE ROBUST INCOMING SEA BREEZE FRONT FROM THE S. BULK OF THE INSTABILITY IS ELEVATED...WITHIN A CORRIDOR OF 6.0-7.0C/KM LAPSE RATES...WHICH WILL SHIFT SE...THEN OFFSHORE IN THE EVENING. EXPECT CONVECTION TO START ACROSS THE HIGHER TERRAIN IN VT/NH THANKS TO ELEVATED HEAT SOURCE BETTER REALIZING THE AVAILABLE INSTABILITY. THEN IT WILL BE A RACE AGAINST TIME AS THIS CONVECTION SHIFTS S AND INTERACTS WITH THE VARIOUS FRONTS /COLD AND SEA BREEZE/ ACROSS SRN NEW ENGLAND. AGREE WITH PREVIOUS FORECASTER THAT THE MOST LIKELY CORRIDOR TO MAINTAIN SOME OF THIS CONVECTION WILL BE AROUND THE I-495 CORRIDOR AND INTO RI...WHERE THE FRONTS ARE LIKELY TO MEET. PLENTY OF INSTABILITY ALOFT WITH ML CAPES EXCEEDING 1000J/KG...BUT WITH THE CORE OF BEST LAPSE RATES SHIFTING OFFSHORE THROUGH THE EVENING...IT MAY STRUGGLE. THEREFORE...FEEL THAT CAPPING BOTH T-STORM AND SHOWER ACTIVITY AT SCT STILL REMAINS THE BEST FORECAST. PWATS NEAR 2 STD DEVIATIONS ABOVE NORMAL...BUT GIVEN THE SCT NATURE IT/S POSSIBLE SEVERAL LOCATIONS STILL REMAIN DRY. SHOULD ANY STORMS HOLD THROUGH THE EVENING...THE UPPER LVL INSTABILITY WILL BE THE ONLY THING TO MAINTAIN UPDRAFTS AS SHEAR IS VERY WEAK. THEREFORE...STILL NOT MENTIONING ANY ENHANCED WORDING WITH THIS UPDATE AS HEAVY RAIN...GUSTY WINDS AND/OR HAIL WOULD BE A VERY ISOLATED EVENT. HEAT CONTINUES ESPECIALLY INLAND...ONSHORE FLOW WILL LIMIT HIGHS FURTHER E. HIGHS RANGE FROM THE 90S W...TO LOW 80S NEAR SHORE. && .SHORT TERM /7 PM THIS EVENING THROUGH 6 PM FRIDAY/... TONIGHT... WITH BACKDOOR FRONT SLOWING AND GRADUALLY DIMINISHING AS IT MOVES OFFSHORE...LINGERING RISK OF ISOLATED -SHRA WILL GIVE WAY TO DRIER CONDITIONS LATE WITH LOSS OF DIURNAL SUPPORT. LITTLE CHANGE IN AIRMASS OVERNIGHT SO WITH DWPTS IN THE 60S SOME FOG STILL POSSIBLE OVER INTERIOR MA/CT ESPECIALLY WHERE/IF RAIN FALLS. ERN MA/RI WILL BE UNDER THE INFLUENCE OF INCREASING PRES GRADIENT AND BREEZY CONDITIONS DURING THE AM HOURS. LOTS OF CLOUD COVER...SO MINS REMAIN IN THE 60S IN SPITE OF COOLER AIRMASS SPILLING OVER FROM THE NE. FRI... BREEZY AND COOLER THANKS TO A COMBINATION OF ONSHORE FLOW AND H85 TEMPS DIPPING TO AROUND +12C BY THE AFTERNOON HOURS. THE HIGH PRES BUILDING OVER WILL LEAD TO STRONG ENOUGH SUBSIDENCE TO LIMIT BL DEPTH. THEREFORE...UNLIKELY MIXING TO H85...LIMITING HIGHS MAINLY IN THE LOW 70S TO LOW 80S INLAND. LOW 70S WILL BE NEAR SHORE...THANKS TO SST/S NEAR THESE VALUES. THE NE WINDS WILL DIMINISH DURING THE AFTERNOON EVEN AS SKIES GRADUALLY CLEAR. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... HIGHLIGHTS... * WARMER THAN NORMAL TEMPERATURES MOST OF THIS PERIOD * MAINLY DRY WEATHER PREVAILS SYNOPTIC OVERVIEW... GEFS AND ECENS ENSEMBLES IN GOOD AGREEMENT THAT SUBTROPICAL RIDGE FROM TEXAS TO THE NORTHEAST STATES WILL DOMINATE OUR WEATHER MUCH OF THIS PERIOD. ITS NOT UNTIL THE MIDDLE OF NEXT WEEK THAT THE NORTHERN STREAM JET BEGINS TO DESCEND SOUTHWARD AND ERODE THE NORTHERN PERIPHERY OF THIS RIDGE. THUS OTHER THAN TEMPERATURES BRIEFLY AT OR COOLER THAN NORMAL FRI NIGHT INTO SAT MORNING...THE REMAINDER OF THIS FORECAST PERIOD WILL BE WARMER THAN NORMAL. IN FACT THE EURO ENSEMBLES SUGGESTING 850 TEMPS WARMING TO +18C ACROSS SNE BY MON AND TUE! GEFS AND DETERMINISTIC GUIDANCE JUST SLIGHTLY LESS AT +16C/+17C. THIS WOULD SUPPORT HIGHS APPROACHING 90 AWAY FROM THE SOUTH COAST. REGARDING PRECIP...SUBTROPICAL RIDGE WILL PROVIDE DRY WEATHER MOST OF THIS PERIOD WITH THE NEXT CHANCE OF CONVECTION THE MIDDLE OF NEXT WEEK AS NORTHERN STREAM JET ENERGY BEGINS TO BREAK DOWN THE NORTHERN PERIPHERY OF THE RIDGE. POTENTIAL WILDCARD NEXT WEEK REGARDING THE AMPLITUDE OF THE NORTHERN STREAM JET ACROSS THE CONUS MAY BE LINKED TO TROPICAL STORM IGNACIO...AS IT HEADS NORTHEAST TOWARD GULF OF ALASKA EARLY NEXT WEEK AND BECOMES ABSORBED AND POTENTIALLY ENERGIZES THE NORTHERN STREAM. DAILY DETAILS... FRI NIGHT/SATURDAY... ANOMALOUS 1025 MB ANTICYCLONE/SURFACE HIGH ADVECTS INTO SNE. THIS MODIFIED CONTINENTAL POLAR AIRMASS WILL COMBINE WITH CLEAR SKIES AND LIGHT WINDS TO YIELD COOL TEMPS FRI NIGHT/SAT AM. SOME OF THE GUIDANCE SUGGESTING THE TYPICALLY COOLER LOCATIONS COULD SEE TEMPS DIP INTO THE U40S! THIS DEEP LAYER RIDGE /H5 HEIGHTS OF 591 DM AND 1024 MB SFC HI/ OVER THE AREA WILL PROVIDE DRY WEATHER WITH TEMPS REBOUNDING INTO THE U70S AND L80S SAT AFTN AFTER A COOL START TO THE DAY. COMFORTABLE HUMIDITY WITH DEW PTS IN THE 50S. SUNDAY AND MONDAY... DEEP LAYER RIDGE REMAINS OVER THE AREA SO DRY WEATHER PREVAILS. RIDGE AXIS IS ACROSS THE REGION SUNDAY AND THEN SLIDES JUST OFF THE SOUTH COAST MON. THIS WILL RESULT IN A GRADUAL WARMING TREND SUN AND MON HOWEVER HUMIDITY LOOKS TO REMAIN TOLERABLE WITH DEW PTS ONLY CLIMBING INTO THE U50S AND L60S. TUESDAY AND WEDNESDAY... SUBTROPICAL RIDGE LINGERS ALONG THE EASTERN SEABOARD. ENSEMBLES AND DETERMINISTIC GUIDANCE SUGGEST A WEAK FRONT APPROACHES TUE BUT MAY JUST WASHOUT AS RIDGE WINS OUT. A MORE SIGNIFICANT FRONT MAY ARRIVE MID TO LATE NEXT WEEK. THUS WARM AND HUMID WEATHER LIKELY TO LINGER INTO TUE AND POSSIBLY WED. && .AVIATION /14Z 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. 10 AM UPDATE... TODAY...MAINLY VFR. THERE IS A MARINE STRATUS DECK /WITH FOG/ DRIFTING EAST OFF LONG ISLAND THAT MAY PRODUCE LOWER CIGS/VSBYS ON BLOCK ISLAND AND NEARBY SOUTH COASTAL WATERS...SHOULD GRADUALLY MIX/LIFT THRU NOON TODAY. LATE AFTERNOON/EVENING WIDELY SCT -SHRA/TSTMS POSSIBLE...WITH LOCALIZED LOWER CATEGORIES. WINDS SHIFT FROM THE SW TO E-NE THROUGH THE DAY. TONIGHT AND FRI... MAINLY VFR AFTER ANY SHOWERS AND LATE NIGHT FOG TONIGHT BURN OFF. BREEZY EARLY FRI. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. SEA-BREEZE EXPECTED TO DEVELOP BY MIDDAY. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/...HIGH CONFIDENCE. VFR THROUGH THE PERIOD. AREAS OF EARLY MORNING IFR CIGS/VSBYS POSSIBLE IN FOG SATURDAY AND SUNDAY. LIGHT FLOW OVER THE WEEKEND WITH SEA BREEZES POSSIBLE SATURDAY. INCREASING WEST-SOUTHWEST FLOW SUNDAY-MONDAY. && .MARINE... 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. TODAY... MARINE CLOUD/FOG BANK DRIFINT EAST FROM LONG ISLAND AND VICINITY...WILL ALLOW FOR PATCHY FOG IN THE VICINITY OF BLOCK ISLAND/LONG ISLAND SOUND AND WATERS SOUTH OF BLOCK ISLAND THRU MIDDAY...POSSIBLY EARLY AFTERNOON. EXPECT THIS CLOUD/FOG BANK TO SLOWLY MIX/LIFT OVER THE NEXT FEW HOURS. OTHERWISE...HIGH PRES WILL MOVE E OF THE WATERS AS A COLD FRONT BACKDOORS FROM THE GULF OF MAINE. MAINLY QUIET BOATING WEATHER PREVAILS...BUT AN ISOLATED SHOWER OR T-STORM LATE TODAY MAY LEAD TO LOCALIZED ROUGH CONDITIONS. TONIGHT INTO EARLY FRI... N-NE WINDS WILL GRADUALLY INCREASE THROUGH THE OVERNIGHT HOURS. GUSTS MAY APPROACH 25-30 KT AT TIMES EARLY AM INTO ABOUT MID DAY. SEAS INCREASE AS WELL...REACHING NEAR 5 FT FIRST ON THE E WATERS...THEN THE OUTER SRN WATERS BY MID DAY. THEREFORE...SMALL CRAFT ADVISORIES HAVE BEEN HOISTED FOR THIS RISK. LATE FRI... CONDITIONS WILL GRADUALLY RECEDE BUT SOME SMALL CRAFT ADVISORIES MA LINGER AS SEAS TAKE A BIT LONGER TO DIMINISH. OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/...HIGH CONFIDENCE. FRI NIGHT THROUGH MONDAY...TRANQUIL BOATING WEATHER THIS PERIOD AS 1025 MB HIGH PRESSURE BUILDS OVER THE WATERS. WIND AND SEAS FRI NIGHT DIMINISH OVER THE WEEKEND TO LIGHT/VARIABLE SATURDAY AND SOUTHWEST SUNDAY-MONDAY. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FROM 8 AM TO 8 PM EDT FRIDAY FOR ANZ231>235-237-254>256. SMALL CRAFT ADVISORY FROM 5 AM TO NOON EDT FRIDAY FOR ANZ230. SMALL CRAFT ADVISORY FROM 5 AM TO 2 PM EDT FRIDAY FOR ANZ236. SMALL CRAFT ADVISORY FROM 5 AM TO 6 PM EDT FRIDAY FOR ANZ250- 251. && $$ SYNOPSIS...NOCERA/DOODY NEAR TERM...NOCERA/DOODY/NMB SHORT TERM...DOODY LONG TERM...NOCERA AVIATION...NOCERA/DOODY MARINE...NOCERA/DOODY/NMB

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