Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 042305 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 705 PM EDT MON MAY 4 2015 .SYNOPSIS... MILD WEATHER PREVAILS THIS EVENING AND OVERNIGHT AHEAD OF AN APPROACHING COLD FRONT. THIS BOUNDARY MAY TRIGGER ISOLATED TO WIDELY SCATTERED SHOWERS TUESDAY. HIGH PRESSURE BUILDS IN BEHIND THIS FRONT WED...PROVIDING MILD TEMPERATURES BUT LOWER HUMIDITY THAN TUESDAY. WARMER WEATHER FOLLOWS THU AND FRI AS THE HIGH SLIPS SOUTH AND THEN EAST OF NEW ENGLAND. A COLD FRONT LATE THIS WEEKEND INTO EARLY NEXT WEEK MAY YIELD SCATTERED SHOWERS. OTHERWISE DRY... WARM AND SLIGHTLY MORE HUMID WEATHER PREVAILS THIS WEEKEND. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 7 PM UPDATE... GUSTY SOUTHWEST WINDS WILL EASE AROUND OR JUST AFTER SUNSET. HOWEVER PERSISTENT SW WINDS WILL ADVECT HIGHER DEW PT AIRMASS INTO THE REGION OVERNIGHT ALONG WITH KEEPING BOUNDARY LAYER WELL MIXED. THIS WILL RESULT IN A MILD EVENING AND OVERNIGHT AHEAD. PREVIOUS FORECAST CAPTURES THESE DETAILS NICELY SO NO MAJOR CHANGES OTHER THAN MODIFYING HOURLY TEMPS/DEW PTS AND WINDS TO BETTER REFLECT CURRENT CONDITIONS. EARLIER DISCUSSION BELOW. ==================================================================== TONIGHT... HIGH PRESSURE CONTINUES TO MOVE OFFSHORE...WHICH WILL PERMIT A COLD FRONT TO APPROACH FROM THE WEST AFTER MIDNIGHT. THIS FRONT IS NOT PARTICULARLY POTENT...AND HAS A LOT OF DRY AIR TO OVERCOME. ANY SHOWERS WILL HOLD OFF UNTIL VERY LATE TONIGHT...AND BE CONFINED PRIMARILY TO NORTHWEST MA. THE INCREASING CLOUDS AND RELATIVELY WARM STARTING POINT WILL KEEP MINIMUM TEMPERATURES WELL ABOVE NORMAL OVERNIGHT...MAINLY IN THE 50S. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... A WEAKENING COLD FRONT WILL PROVIDE A FOCUS FOR ISOLATED TO SCATTERED SHOWERS ACROSS SOUTHERN NEW ENGLAND. INSTABILITY IS NOT GREAT...BUT CANNOT COMPLETELY RULE OUT THE POSSIBILITY OF AN ISOLATED THUNDERSTORM OR TWO. THE MOST LIKELY SCENARIO IS FOR SCATTERED SHOWERS...ESPECIALLY DURING THE MORNING HOURS. THE FRONT CONTINUES TO WEAKEN DURING THE AFTERNOON...WITH WEAK RIDGING ARRIVING DURING TUESDAY EVENING AND OVERNIGHT. THIS SHOULD MEAN A SLOW DRYING TREND TUESDAY NIGHT. TEMPERATURES WILL STILL BE SLIGHTLY ABOVE NORMAL TUESDAY AND TUESDAY NIGHT. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... 348 PM UPDATE... HIGHLIGHTS... * SPRING TO SUMMER-LIKE TEMPS MUCH OF THE PERIOD * MAINLY DRY WEATHER WED THRU SAT WITH INCREASING RISK OF SHOWERS SUN/MON SYNOPTIC OVERVIEW AND MODEL/GUIDANCE EVALUATION... 00Z ECENS/EPS AND 12Z GEFS ENSEMBLES IN GOOD AGREEMENT ON THE LARGE SCALE FLOW THIS PERIOD WHICH FEATURES AN ANOMALOUS CLOSED LOW EVOLVING OVER THE NORTHWEST ATLANTIC OF ABOUT -3 STD DEVIATIONS FROM CLIMO...ALONG WITH A RIDGE CENTERED OVER THE GREAT LAKES AND OHIO VALLEY. THIS PLACES NEW ENGLAND IN A DRY NORTHWEST FLOW REGIME WED THRU FRI. BY THE WEEKEND THE UPPER AIR PATTERN BECOMES SOMEWHAT PROGRESSIVE WITH THE CLOSED LOW MOVING INTO THE CENTRAL ATLANTIC ALLOWING GREAT LAKES RIDGE/HEIGHT ANOMALY TO ADVECT EASTWARD INTO NEW ENGLAND...CONTINUING THE DRY WEATHER INTO AT LEAST THE FIRST HALF OF THE WEEKEND. THEN BY LATE IN THE WEEKEND AND ESPECIALLY EARLY NEXT WEEK THE QUESTION BECOMES HOW QUICKLY DOES THE RIDGE ERODE AS UPSTREAM TROUGH APPROACHES. IN ADDITION...RIDGE BECOMES SOMEWHAT OF A DIRTY RIDGE WITH MOISTURE FROM REMNANT CLOSED LOW OVER THE SOUTHEAST STATES ADVECTING NORTHWARD UP THE EASTERN SEABOARD. AS EXPECTED AT THIS TIME RANGE THE DETERMINISTIC RUNS OF THE 12Z ECMWF AND 12Z GFS HANDLE THIS DIFFERENTLY ALONG WITH ENSEMBLES. THUS FORECAST CONFIDENCE BECOMES LOW ON SHOWER POTENTIAL LATER THIS WEEKEND INTO EARLY NEXT WEEK. TEMPERATURES... BRIEF COOL DOWN OR BETTER LABELED AS NOT AS WARM WED /LOW TO MID 70S/ IN THE POST FRONTAL AIRMASS ALONG WITH LOWER DEW PTS /30S/. HOWEVER AS SURFACE HIGH SLIPS SOUTH OF NEW ENGLAND THU...SURFACE WINDS BECOME WSW AND THIS WILL SUPPORT TEMPS WARMING TO 75 TO 80 AND POTENTIALLY CLIMBING INTO U70S AND L80S BY FRI. WARM WEATHER CONTINUES SAT WITH HIGHS IN THE L80S AWAY FROM THE SOUTH COAST. IN ADDITION WITH SSW SURFACE WINDS DEW PTS WILL CLIMB INTO THE 50S. STILL COMFORTABLE BUT THIS WILL RESULT IN NIGHTLY TEMPS NOT AS COOL ALONG WITH PATCHY FOG. SUNDAY...TRICKY AS POTENTIAL BACKDOOR FRONT IMPACTS EASTERN MA AND POSSIBLY RI. NOT AS WARM EARLY NEXT WEEK GIVEN LIKELY CLOUD COVER...SOUTHERLY FLOW AND RISK OF SHOWERS. HOWEVER TEMPS WILL STILL AVERAGE WARMER THAN NORMAL. PRECIPITATION... AS MENTIONED ABOVE DRY PATTERN PREVAILS WED THRU FRI AND PROBABLY INTO SAT. RISK OF SHOWERS INCREASES SUNDAY AS UPSTREAM TROUGH APPROACHES ALONG WITH REMNANT MOISTURE OFFSHORE FROM CLOSED LOW OVER THE SOUTHEAST STATES LATER THIS WEEK. HOWEVER GREATEST RISK OF SHOWERS APPEARS TO BE EARLY NEXT WEEK AS UPSTREAM TROUGH GETS CLOSER TO THE REGION AND BEGINS TO INTERACT WITH DEEPER MOISTURE ALONG AND OFF THE EASTERN SEABOARD. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. HIGH CONFIDENCE THROUGH TUE NIGHT. 7 PM UPDATE... ONLY CHANGE IS TO ADD LLWS TO TAF SITES IN EASTERN MA AND RI FOR LOW LEVEL SOUTHWEST JET OF UP TO 50 KT PEAKING AROUND 06Z TONIGHT. EARLIER DISCUSSION BELOW. ================================================================= SW WINDS MAY BRING SOME 20-25KT GUSTS THROUGH EARLY EVENING...OTHERWISE VFR THROUGH TONIGHT. VFR CIGS TUE AS COLD FRONT DROPS THROUGH SOUTHERN NEW ENGLAND...WITH SCATTERED SHOWERS POSSIBLE. MAY SEE SOME MVFR CIGS NEAR S COAST TUE AFTERNOON. VFR TUE NIGHT. KBOS TAF...HIGH CONFIDENCE IN TAF. KBDL TAF...HIGH CONFIDENCE IN TAF. OUTLOOK...WEDNESDAY THROUGH SATURDAY... 348 PM UPDATE... HIGH CONFIDENCE FOR VFR AND DRY WEATHER. LOW RISK FOR PATCHY FOG EACH NIGHT BETWEEN MIDNIGHT AND SUNRISE WITH LOCAL IFR CIGS/VSBYS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH TUESDAY/... 4430 PM UPDATE... TONIGHT INTO TOMORROW...MODERATE CONFIDENCE. THE SW FLOW WILL SLOWLY GIVE WAY TO W FLOW AS A COLD FRONT CROSS THE WATERS DURING THE TUE EVENING HOURS. WITH THE PERSISTENT SW FLOW TODAY...SOME CONCERN WIND-DRIVEN SEAS COULD APPROACH 5 FT ON THE OCEAN WATERS. IT IS MARGINAL...BUT DID HAVE ENOUGH CONFIDENCE TO ISSUE A SMALL CRAFT ADVISORY ACROSS THE OUTER COASTAL WATERS. THE MAIN RISK WILL BE ROUGH SEAS...BUT COULD SEE A FEW GUSTS TO 25 KT AS WELL AHEAD OF A COLD FRONT. CONDITIONS IMPROVE TUESDAY AFTERNOON. SOME SHOWERS...WITH POSSIBLY EVEN A THUNDERSHOWER. TUESDAY NIGHT...WINDS AND SEAS CONTINUE TO DIMINISH. OUTLOOK...WEDNESDAY THROUGH SATURDAY... 348 PM UPDATE... WEDNESDAY...HIGH PRES OVER THE WATERS WITH TRANQUIL/DRY WEATHER AND GOOD VSBY. HIGH FORECAST CONFIDENCE. THURSDAY...HIGH SLIPS SOUTH OF NEW ENGLAND WITH WINDS BECOMING SSW. TRANQUIL/DRY WEATHER WITH GOOD VSBY CONTINUES. FRIDAY...HIGH PRES MOVES EAST OF NEW ENGLAND. DRY/TRANQUIL WEATHER CONTINUES. && .FIRE WEATHER... RED FLAG WARNING REMAINS POSTED PRIMARILY FOR THE TERRAIN INFLUENCE IN WESTERN MASSACHUSETTS. TEMPERATURES IN THE UPPER 70S AND LOWER 80S WILL COMBINE WITH DEWPOINTS IN THE UPPER 30S AND LOW 40S TO YIELD MIN RH VALUES AROUND 20 PERCENT THIS AFTERNOON. SW WINDS 10 TO 15 MPH WILL OCCASIONALLY GUST TO 20-25 MPH THROUGH 7 PM. SCATTERED SHOWERS EXPECTED TUE...BUT RAINFALL AMOUNTS SHOULD BE UNDER 0.25 INCH. LIGHT W/NW WINDS EXPECTED WITH MORE CLOUD COVER. 348 PM UPDATE... THURSDAY...LOW RISK OF ELEVATED FIRE WEATHER CONCERNS WITH MIN RH VALUES DIPPING TO 25 TO 30 PERCENT ALONG WITH WSW WIND GUSTS UP TO 20 MPH. SUSTAINED WINDS WILL BE LESS 10-15 MPH BUT AGAIN GUSTS UP TO 20 MPH AND PERHAPS 25 MPH ARE POSSIBLE. WHILE ISOLATED OR WIDELY SCATTERED SHOWERS ARE POSSIBLE TUE MOST OF THE REGION WILL BE DRY WITH ANY RAINFALL LIKELY LESS THAN 0.25 INCHES. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...RED FLAG WARNING UNTIL 9 PM EDT THIS EVENING FOR MAZ002>004- 008>012-026. RI...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR ANZ230>237-251. SMALL CRAFT ADVISORY FROM 1 AM TO 9 AM EDT TUESDAY FOR ANZ235. SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 9 AM EDT TUESDAY FOR ANZ250. SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 3 PM EDT TUESDAY FOR ANZ254. SMALL CRAFT ADVISORY FROM 1 AM TO 3 PM EDT TUESDAY FOR ANZ255- 256. && $$ SYNOPSIS...NOCERA NEAR TERM...BELK/NOCERA/JWD SHORT TERM...BELK LONG TERM...NOCERA AVIATION...NOCERA/JWD MARINE...BELK/NOCERA FIRE WEATHER...

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