Area Forecast Discussion
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000 FXUS61 KBOX 271154 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 754 AM EDT WED AUG 27 2014 .SYNOPSIS... HIGH PRESSURE OFFSHORE WILL DRAW WARM AIR ACROSS NEW ENGLAND TODAY. A COLD FRONT WILL THEN SWEEP THROUGH DURING THE LATE AFTERNOON AND EARLY NIGHT. DRY AND COOLER CONDITIONS RETURN THURSDAY AND FRIDAY BEHIND THE FRONT. HURRICANE CRISTOBAL WILL PASS WELL OFFSHORE LATE TONIGHT INTO THURSDAY MORNING...BUT WILL BRING ROUGH SURF AND RIP CURRENTS TO SOUTH FACING BEACHES. A FRONT MAY STALL ACROSS NEW ENGLAND...BRINGING UNSETTLED CONDITIONS SUNDAY INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 730 AM UPDATE... OTHER THAN A FEW PATCHES OF DENSE FOG...SKIES WERE MAINLY CLEAR WITH SOME HIGH CIRRUS STARTING TO MOVE INTO CENTRAL AND NORTHERN AREAS AT 11Z. TEMPS BOTTOMED OUT MAINLY IN THE 60S WITH A FEW SPOTS DROPPING DOWN TO THE UPPER 50S INCLUDING KOWD...KTAN...KORE AND KEEN. FORECAST IS ON TRACK THIS MORNING OTHER THAN TEMPS/DEWPTS. BROUGHT THOSE ELEMENTS CURRENT AND INCORPORATED INTO NEAR TERM TRENDS. PREVIOUS DISCUSSION... COLD FRONT APPROACHES FROM THE ST LAWRENCE VALLEY WITH A BAND OF THICKER CLOUDS. MEANWHILE SUN THIS MORNING AND MIDDAY WILL GENERATE SUFFICIENT MIXING TO REACH 850 MB...WHERE TEMPS ARE 16-17C. IF WE ATTAIN FULL MIXING THEN MAX TEMPS SHOULD REACH NEAR 90. INCREASING SKY COVER AS THE FRONT APPROACHES MAY LIMIT MAX TEMPS A FEW DEGREES BELOW THIS. MAIN QUESTION WILL BE THE POTENTIAL FOR CONVECTION AND ITS SEVERITY. INSTABILITY FIELDS FROM THE ECMWF ARE SOMEWHAT SUPPORTIVE OF CONVECTION WITH TOTALS IN THE MID 40S AND CAPE 500-700 J/KG...WHILE THE GFS HAS SIMILAR MID 40S TOTALS BUT IS MORE GUNG- HO WITH CAPE 1500-2000 J/KG. EVEN WITH THE MILDER ECMWF VALUES...GENERAL THUNDER IS REASONABLE. WE WILL CONTINUE TO ADVERTISE CHANCE POPS FOR SHOWERS/TSTMS. SEVERE STORMS ARE LESS LIKELY. MOST OF THE FAVORABLE DYNAMICS WILL BE NORTH AND WEST THROUGH THE AFTERNOON/EVENING. WINDS AT 850 MB WILL BE MOSTLY BELOW 20 KNOTS WHILE 500 MB WINDS OF 35 KNOTS OR HIGHER ARE AT BEST REACHING OUR EXTREME NORTHWEST AREAS AROUND 00Z...NEAR SUNSET. PRECIP WATER VALUES INCREASE DURING THE AFTERNOON WITH GFS AND NAM SHOWING 1.75 TO 2.0 INCHES. EVEN IF WE STAY NEARER TO 1.5 INCHES...THIS WILL BE AROUND 1.5-1.9 STD DEVIATIONS ABOVE NORMAL. PUTTING IT TOGETHER...CAN/T RULE OUT ISOLATED SEVERE WIND GUSTS BUT BETTER CHANCE OF A FEW LOCALLY HEAVY DOWNPOURS. OTHER CONCERN WILL BE INCREASING SWELL FROM HURRICANE CRISTOBAL. FIVE FOOT SWELL DOESN/T ARRIVE IN THE SOUTHERN WATERS UNTIL AFTER 00Z. WHILE CONDITIONS MAY DETERIORATE A LITTLE DURING THE DAY...EXPECT THE SIGNIFICANT CHANGES TO HOLD OFF UNTIL AFTER SUNSET. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... TONIGHT... CONSENSUS OF THE MODEL SOLUTIONS BRINGS THE COLD FRONT TO THE COASTAL PLAIN AROUND SUNSET AND OFFSHORE EARLY TONIGHT. EXPECT LINGERING SHOWER/TSTM THROUGH 10 PM IN RI AND EASTERN MASS...AND THROUGH MIDNIGHT CAPE AND ISLANDS. WINDS TURN NORTHWEST BEHIND THE COLD FRONT AND DRAW COOLER DRIER AIR DOWN FROM CANADA. THIS WILL MEAN CLEARING SKIES AND DEW POINTS IN THE 50S AND LOWER 60S. SWELL FROM HURRICANE CRISTOBAL CONTINUES TO INCREASE...WITH 5 FOOT SWELL MOVING INTO OUR SOUTHERN WATERS EARLY TONIGHT. WE HAVE ISSUED A HIGH SURF ADVISORY STARTING TONIGHT. THURSDAY... UPPER SHORTWAVE MOVES ACROSS NEW ENGLAND WITH BRIEF COOLING ALOFT. MOISTURE FIELDS SHOW LINGERING 80 PCT RH VALUES BETWEEN 800 AND 900 MB. THIS SUGGESTS DIURNAL CUMULUS WILL FORM DURING THE DAY. MIXING WILL REACH TO 850 MB WHERE TEMPS OF 10-12C WOULD SUPPORT MAX SFC TEMPS IN THE UPPER 70S AND LOW 80S. WINDS ALOFT WITHIN THE MIXED LAYER ARE FORECAST AT 20 KNOTS...WHICH MAY GET MIXED TO THE SURFACE IN GUSTS. HIGH SURF WILL CONTINUE THROUGH THE DAY AS CRISTOBAL PASSES WELL OFFSHORE. THE HIGH SURFACE ADVISORY WILL CONTINUE THROUGH THE DAY. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... HIGHLIGHTS... * COOL AND DRY WEATHER UNDER HIGH PRESSURE FRIDAY * WARM AND HUMID CONDITIONS INTO THE WEEKEND * SCT SHOWERS/THUNDERSTORMS SUNDAY INTO EARLY NEXT WEEK OVERVIEW AND MODEL PREFERENCES... MEDIUM RANGE MODELS AND THEIR ENSEMBLES ALL CONTINUE TO SIGNAL A LOW AMPLITUDE UPPER LEVEL PATTERN ACROSS THE NORTHERN TIER STATES... WHICH GENERALLY MEANS A FAST MOVING PATTERN IN PLACE. NOTING A DECENT SHORT WAVE DEVELOPING ACROSS THE GREAT LAKES LATE THIS WEEK...THEN PUSHING ALONG IN THE GENERAL W-NW UPPER FLOW TOWARD NEW ENGLAND. A FRONT ALSO TRIES TO SHIFT S...BUT BECOMES PARALLEL TO THIS UPPER FLOW...SO MAY SEE UNSETTLED CONDITIONS MOVE IN FOR SUNDAY AND LABOR DAY. NOTING INCREASING VARIANCE AMONGST THE OP MODEL RUNS EARLY NEXT WEEK IN TRYING TO CLEAR THE SHORT WAVE...WITH POSSIBLY ANOTHER WEAKER ONE MOVING IN. LEANED TOWARD A BLEND OF AVAILABLE MODELS FOR THE EARLY PORTION OF THE FORECAST...WHICH SHOWED GOOD CONTINUITY AND RUN TO RUN CONSISTENCY OVER THE LAST SEVERAL MODEL RUNS...THEN TRENDED TOWARD THE GFS/EC ENSEMBLES BEGINNING SUNDAY THROUGH TUESDAY. DETAILS... THURSDAY NIGHT THROUGH FRIDAY NIGHT... EXPECT DRY AND COOL CONDITIONS AS LARGE HIGH PRES BUILDS OUT OF THE GREAT LAKES...SHIFTING E IN THE BROAD UPPER LEVEL WESTERLY WIND FLOW. WILL MAINLY CLEAR SKIES THU NIGHT AND WINDS BECOMING LIGHT/VRBL MAINLY AFTER MIDNIGHT...TEMPS WILL TUMBLE...WITH READINGS AWAY FROM THE IMMEDIATE COAST AND URBAN CENTERS DROPPING TO THE MID 40S TO AROUND 50. SOME DIURNAL CLOUDS WILL DEVELOP DURING FRIDAY...BUT IT WILL REMAIN COOL WITH HIGHS MAINLY IN THE LOWER-MID 70S. NW WINDS MAY GUST UP TO AROUND 20 KT DURING THE AFTERNOON. CONDITIONS WILL REMAIN DRY FRI NIGHT...BUT THE HIGH WILL CREST ACROSS THE REGION OVERNIGHT. EXPECT SOME MID AND HIGH LEVEL CLOUDS WORKING IN WITH LOWS IN THE 50S. SATURDAY... TRANSITION DAY AS H5 SHORT WAVE MOVES OUT OF THE GREAT LAKES. TEMPS WILL REBOUND AS W-SW WINDS KICK IN...BRINGING IN THE MILDER CONDITIONS WITH INCREASING HUMIDITY ESPECIALLY LATE IN THE DAY INTO SAT NIGHT. A FRONT WILL BEGIN TO SLOWLY SHIFT S OUT OF QUEBEC AND S ONTARIO...SO MAY START TO SEE SOME SHOWERS MOVE INTO WESTERN AREAS SAT NIGHT. CARRIED ONLY LOW CHANCE POPS AT THIS POINT. HIGHS WILL BE IN THE 70S...UP TO AROUND 80 IN THE CT AND MERRIMACK VALLEYS. SUNDAY THROUGH MONDAY... WITH THE HIGH ANCHORED OFF THE MID ATLC AND SE U.S. COAST...ALONG WITH GENERAL W WIND FLOW ALOFT...THE FRONT THAT TRIES TO PUSH S WILL GET HUNG UP IN THIS UPPER FLOW. THE SHORT WAVE WILL MOVE ALONG THE FRONT...SO WILL SEE SCT SHOWERS PUSH ACROSS SUNDAY INTO THE HOLIDAY...WITH BEST SHOT SUNDAY NIGHT AND MON MORNING. DEWPTS ALSO INCREASE. PWATS WILL ALSO INCREASE...ON ORDER OF 1.7 TO 1.8 INCHES /ABOUT +2 SD FOR LATE AUGUST/. SOME MARGINAL INSTABILITY ALSO WORKS IN...SO CAN NOT RULE OUT SOME THUNDERSTORMS. MAY ALSO SEE A FEW PRODUCING LOCALLY HEAVY RAINFALL. TEMPS WILL RISE TO THE UPPER 70S TO MID 80S...MILDEST ON SUNDAY...WITH DEWPTS RISING TO THE MID 60S BOTH DAYS. TUESDAY... SOME QUESTION AS TO TIMING OF EXIT OF PRECIP...AND WHETHER ANOTHER SHORT WAVE DEVELOPS AND PUSHES TOWARD THE REGION. FOR NOW...EXPECT MAINLY DRY BUT WARM CONDITIONS...BUT NOT A LOT OF CONFIDENCE FOR THIS PORTION OF THE FORECAST. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /TODAY THROUGH THURSDAY/...MODERATE CONFIDENCE. TODAY...MOSTLY VFR. SCATTERED SHOWERS/TSTMS SHOULD DEVELOP THIS AFTERNOON...INITIALLY INLAND FROM AROUND MHT TO BAF AND BDL BUT THE POTENTIAL SPREADS E TO BOS-PVD LATER IN THE DAY. BRIEF MVFR/IFR UNDER THE CORE OF ANY SHOWERS/STORMS...ALSO BRIEF HEAVY RAIN AND MAYBE A STRONG WIND GUST. LOW CONFIDENCE ON TIMING. TONIGHT...MOSTLY VFR. ANY LINGERING SHOWERS/TSTMS IN EASTERN MASS/RI WILL MOVE OFFSHORE OR DISSIPATE DURING THE FIRST PART OF THE NIGHT. WINDS THEN BECOME NORTHWEST OVERNIGHT AS THE COLD FRONT MOVES OFFSHORE. THURSDAY...VFR. NORTHWEST WINDS MAY GUST TO 20 KNOTS WITH SCATTERED TO BROKEN SKY COVER AROUND 5000 FEET FROM MIDDAY TO EVENING. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. SW-WINDS PREVAILING. SCT SHRA/TSRA POSSIBLE AROUND 21Z...LOW CONFIDENCE ON DIRECT HIT FOR TERMINAL SO NO MENTION AT THIS TIME. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. SW-WINDS PREVAILING. SCT SHRA/TSRA POSSIBLE AROUND 19Z...LOW CONFIDENCE ON DIRECT HIT FOR TERMINAL SO NO MENTION AT THIS TIME. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY... THURSDAY NIGHT INTO FRIDAY...HIGH CONFIDENCE. VFR WITH SKC THURSDAY NIGHT INTO FRIDAY. LIGHT WINDS. PATCHY FOG AFTER 06Z FRI WITH LOCAL MVFR TO IFR CONDITIONS POSSIBLE IN NORMALLY PRONE AREAS. SEA BREEZES FRIDAY. SATURDAY INTO SUNDAY...MODERATE CONFIDENCE. VFR. INCREASING S-SW WINDS. BETTER CHANCES FOR SHRA/TSRA SUNDAY ACROSS THE INTERIOR. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /TODAY THROUGH THURSDAY/...HIGH CONFIDENCE. TODAY...HIGH PRESSURE OVER THE WATERS WILL SHIFT FARTHER OFFSHORE. EXPECT LIGHT WINDS/PATCHY FOG FIRST THING THIS MORNING...OTHERWISE GOOD VSBY WITH SOUTHWEST WINDS 10-15 KNOTS. AN APPROACHING COLD FRONT MAY BRING SCATTERED SHOWERS/TSTMS TOWARD EVENING. TONIGHT...INCREASING SOUTH SWELL FROM HURRICANE CRISTOBAL. THE SOUTHERN WATERS WILL EXPERIENCE A 5 FOOT SWELL IN THE EARLY NIGHT AND 6 TO 8 FOOT SWELL BY MORNING. THURSDAY...SOUTH SWELL CONTINUES THROUGH THE DAY WITH 6 TO 9 FOOT SEAS...MAINLY SWELL...ON THE SOUTHERN WATERS. NORTHWEST WIND WILL BE GUSTY NEAR SHORE WITH MAXIMUM GUSTS AROUND 20 KNOTS. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY... THURSDAY NIGHT...HIGH CONFIDENCE. EXPECT S SWELL FROM HURRICANE CRISTOBAL TO CONTINUE THROUGH THE NIGHT...THOUGH MAY START TO SUBSIDE LATE. SEAS UP TO 7-9 FT ON THE OUTER WATERS. N-NW WIND GUSTS UP TO 20 KT ON THE EASTERN OUTER WATERS. FRIDAY...HIGH CONFIDENCE. N WINDS GUSTING TO 20 KT EARLY...THEN WILL VEER TO E-NE AND DIMINISH DURING THE DAY. SEAS MAY LINGER AT AROUND 5 FT ON THE OUTER WATERS DURING THE DAY BEFORE SUBSIDING. SATURDAY AND SUNDAY...MODERATE CONFIDENCE. WINDS BECOME S-SW DURING SAT AND CONTINUE THROUGH SUN. GUSTS SHOULD REMAIN BELOW SMALL CRAFT CRITERIA...BUT SEAS MAY BUILD UP TO AROUND 5 FT ON THE SOUTHERN OUTER WATERS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...AIR QUALITY ALERT FROM 1 PM THIS AFTERNOON TO 9 PM EDT THIS EVENING FOR CTZ002>004. MA...HIGH SURF ADVISORY FROM 8 PM THIS EVENING TO 8 PM EDT THURSDAY FOR MAZ020-022>024. NH...NONE. RI...HIGH SURF ADVISORY FROM 8 PM THIS EVENING TO 8 PM EDT THURSDAY FOR RIZ006>008. AIR QUALITY ALERT FROM 11 AM THIS MORNING TO 11 PM EDT THIS EVENING FOR RIZ001>005. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 5 PM THIS AFTERNOON TO 8 PM EDT THURSDAY FOR ANZ235-237-254>256. && $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB/EVT SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/EVT MARINE...WTB/EVT

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