Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 151836 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 236 PM EDT WED APR 15 2015 .SYNOPSIS... HIGH PRESSURE TODAY PROVIDES DRY WEATHER AND WARMER THAN NORMAL TEMPERATURES. DRY BUT SEASONABLY COOL WEATHER FOLLOWS THURSDAY. HIGH PRESSURE MOVES OFFSHORE FRIDAY WITH A PERIOD OF RAIN POSSIBLE. A COLD FRONT CROSSES THE AREA LATE SATURDAY. WEAK HIGH PRESSURE FOLLOWS SUNDAY. LOW PRESSURE APPROACHES EARLY NEXT WEEK WITH THE THREAT OF WIDESPREAD RAIN LATER MARATHON MONDAY INTO TUESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 2 PM UPDATE... THE FEW BANDS OF CIRRUS CLOUDS THAT WERE FLIRTING ALONG THE S COAST HAVE PUSHED OFFSHORE...THOUGH STILL SEE A COUPLE OF SPOTS WITH SOME HIGH CLOUDS HANGING NEAR THE ISLANDS AT 18Z. WITH LARGE HIGH PRES PUSHING E OUT OF QUEBEC AND THE GREAT LAKES...EXPECT THESE CLOUDS TO REMAIN S OF THE REGION THROUGH THE REMAINDER OF THE DAY. HAVE NOTED A FEW DIURNAL CUMULUS CLOUDS HAVE DEVELOPED ACROSS E MA INTO RI AROUND MIDDAY...BUT SHOULD SEE THOSE DISSIPATE BY 21Z-22Z. N-NE WINDS ACROSS EASTERN AREAS AND N-NW WINDS ACROSS THE CENTRAL AND WEST HAVE PICKED UP...WITH BRIEF GUSTS OVER 25 KT IN THE CT VALLEY AROUND MIDDAY /NOTED 32 KT GUST AT KBDL AT 17Z/ BUT LOOK TO BE DIMINISHING ACROSS W MA/N CENTRAL CT AT 18Z. A SEA BREEZE HAS ACTUALLY KICKED AT KBOS AT 18Z. CURRENT FORECAST LOOKS ON TRACK...BUT HAVE UPDATED NEAR TERM TO BRING CONDITIONS CURRENT. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... TONIGHT... WINDS RELAX AS HIGH PRESSURE BUILDS INTO THE REGION. EXPECTING LIGHT AND VARIABLE WINDS UNDER MOSTLY CLEAR CONDITIONS. SHOULD SEE DECENT RADIATIONAL COOLING AND THUS HAVE GONE WITH A CONSENSUS BLEND OF MOS GUIDANCE...DROPPING IT A COUPLE OF DEGREES ESPECIALLY IN SUSCEPTIBLE LOW-LYING AREAS PRONE TO RADIATIONAL COOLING. FROST AND FREEZE HEADLINES ARE NOT NECESSARY AT THIS TIME AS THE GROWING SEASON DOES NOT BEGIN TILL APRIL 21ST FOR LOW- LYING COASTAL AREAS. THURSDAY... HIGH PRESSURE PUSHES E ALLOWING FOR RETURN S-FLOW. MOSTLY CLEAR FORECAST WITH LOW DEWPOINTS AS TEMPERATURES WARM TO THE 60-DEGREE MARK. CONTINUED BOUNDARY-LAYER MIXING ALBEIT LIMITED TO H9 BY A DRY-AIR INVERSION. INFLUENCE OF HIGH PRESSURE SHOULD KEEP WINDS BELOW THE 25 MPH THRESHOLD...CAN NOT RULE OUT GUSTS UP TO 20 MPH WITH THE MIX-DOWN OF FASTER MOMENTUM AND DRIER AIR. WILL NEED TO RE-EVALUATE WITH THE NEXT FORECAST PERIOD WITH RESPECT TO THE FIRE WEATHER ENVIRONMENT. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... SYNOPTIC OVERVIEW... CLOSED LOW OVER THE FOUR CORNERS REGION SUPPORTS SPLIT FLOW ACROSS THE CONUS INTO EARLY THIS WEEKEND. THIS CLOSED LOW EJECTS SEVERAL PACKETS OF SOUTHERN STREAM MOISTURE NORTHEASTWARD INTO NEW ENGLAND WITH THE FIRST MOISTURE PLUME ARRIVING FRI. THE NEXT PACKET OF JET ENERGY AND MOISTURE TARGET SNE EARLY NEXT WEEK. THIS 2ND PRECIP EVENT MAY BE MORE WIDESPREAD AND ASSOCIATED WITH APPRECIABLE QPF AS STREAMS MERGE AND FORMS A COASTAL LOW. MEANWHILE THE NORTHERN STREAM UNDERGOES SOME AMPLIFICATION AS TROUGHING DEVELOPS VICINITY OF ALASKA WITH DOWNSTREAM RIDGING INTO WESTERN CANADA. THIS RESULTS IN A MODEST SURGE OF COOL AIR INTO THE NORTHEAST SAT NIGHT AND SUN MORNING BEHIND A DEPARTING NORTHERN STREAM SHORT WAVE TROUGH/COLD FRONT. MODEL/GUIDANCE EVALUATION... FIRST ITEM OF CONCERN ARE POPS AND QPF FOR FRI. 00Z GFS IS MOST BULLISH WITH QPF. MEANWHILE ALL OTHER GUIDANCE HAS LIGHTER AMOUNTS ALONG WITH PRECIP BECOMING FRAGMENTED ESPECIALLY EASTWARD WHICH SEEMS REASONABLE AS PRECIP ENTERS CONFLUENT FLOW ALOFT OVER NEW ENGLAND. GEFS POPS FOR 0.05 QPF CAPTURES THIS NICELY WITH POPS DIMINISHING FROM WEST TO EAST FRI. THUS WILL FOLLOW A NON GFS SOLUTION HERE YIELDING LESS QPF. NEXT ISSUE IS TIMING OF PRECIP FOR MARATHON MONDAY. DETERMINISTIC 00Z GFS AND 00Z ECMWF ALONG WITH GEFS ENSEMBLES IN GOOD AGREEMENT FOR DRY WEATHER MON MORNING WITH INCREASING CHANCES FOR RAIN IN THE AFTERNOON AND BEYOND. GIVEN GOOD MODEL AGREEMENT WILL FOLLOW THIS TIMELINE. DAILY SENSIBLE WEATHER... THU NIGHT...MILD NIGHT AS RETURN FLOW ADVECTS DEW PTS NEAR 50 ACROSS THE REGION. ANY RAIN SHOULD HOLD OFF TIL VERY LATE AT NIGHT OR FRI MORNING. FRIDAY...HIGH CERTAINTY FOR SCATTERED SHOWERS BUT STILL SOME UNCERTAINTY REGARDING HOW WIDESPREAD AND ASSOCIATED QPF. DOESN/T APPEAR AS A WASHOUT GIVEN FAST FLOW ALOFT MAY YIELD RAIN ENDING IN THE AFTERNOON WITH PARTIAL CLEARING POSSIBLE. SATURDAY...MILD START AND WARM ADVECTION AHEAD OF APPROACHING SHORT WAVE AND ATTENDING COLD FRONT SHOULD SUPPORT A WARM AFTERNOON WITH HIGHS IN THE U60S TO L70S. LEANED TOWARD THE WARMER MOS TEMPS COMPARED TO COOLER MODEL BLEND TEMPS. SOME UNCERTAINTY REGARDING POTENTIAL FOR AFTERNOON AND EVENING SHOWERS. BEST INSTABILITY /STEEPENING LAPSE RATES/ AND FORCING FOR ASCENT APPEARS ACROSS NORTHERN AND EASTERN MA. THUS HIGHEST POPS ACROSS THIS REGION. SUNDAY...COOLER AND DRY BEHIND DEPARTING SHORT WAVE AND ATTENDING COLD FRONT. ALTHOUGH SEASONABLY MILD WITH HIGHS U50S TO L60S...FEW DEGS ABOVE NORMAL. EARLY NEXT WEEK INCLUDING MARATHON MONDAY...FAIRLY HIGH CONFIDENCE IN WIDESPREAD RAIN SOMETIME LATER MONDAY INTO MONDAY NIGHT AND AT LEAST EARLY TUE. RAIN COULD BE WIDESPREAD IN AREAL COVERAGE ALONG WITH APPRECIABLE RAINFALL GIVEN GULF MOISTURE...STREAMS MERGING RESULTING IN A COASTAL LOW TRACKING NEAR OR OVER SOUTHERN NEW ENGLAND. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY/...HIGH CONFIDENCE. THROUGH 00Z...VFR. N-NW WINDS GUSTING TO 25 KT THROUGH 19Z-20Z THEN DIMINISHING. E-NE WINDS FROM KBOS SOUTH TO CAPE COD AND THE ISLANDS IN PLACE...EXCEPT BRIEF SEA BREEZE AT KBOS THAT WILL BECOME E-NE BY AROUND 21Z. TONIGHT...VFR SKC. WINDS BECOME LIGHT/VRBL OR CALM AS HIGH PRES BUILDS OVER. THURSDAY...VFR. SKC THROUGH MIDDAY...THEN HIGH CLOUDS START TO MOVE INTO WESTERN AREAS DURING THE AFTERNOON. LIGHT E-SE WINDS VEER TO S AND INCREASE TO AROUND 10 KT DURING THE AFTERNOON. KBOS TAF...HIGH CONFIDENCE IN TAF. BRIEF SEA BREEZE SHOULD BECOME E-NE BY AROUND 21Z. KBDL TAF...HIGH CONFIDENCE IN TAF. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY... THURSDAY NIGHT...HIGH CONFIDENCE FOR VFR FRIDAY...MODERATE CONFIDENCE. MAINLY VFR BUT WITH PERIODS OF MVFR IN SCATTERED RAIN SHOWERS. SATURDAY...MOST LIKELY VFR WITH A MODEST WEST WIND BECOMING NORTHWEST. SUNDAY...MOST LIKELY VFR ALONG WITH DIMINISHING WINDS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM /THROUGH THURSDAY/...HIGH CONFIDENCE. THIS AFTERNOON...EXPECT N-NE WINDS GUSTING UP TO 25 KT. SEAS REMAIN BELOW 5 FT...BUT MAY POSSIBLY SEE BRIEF SWELLS UP TO 5 FT ACROSS THE FAR SOUTHERN OUTER WATERS. TONIGHT AND THURSDAY...LIGHT AND VARIABLE WINDS OVERNIGHT AS HIGH PRES MOVES ACROSS THE WATERS...THEN SHIFTS E ON THURSDAY ALLOWS FOR RETURN S FLOW THAT BECOMES BRISK WITH GUSTS UP TO 20 KTS TOWARDS THE END OF THE DAY. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY... THURSDAY NIGHT AND FRIDAY...MODEST WSW WINDS AS HIGH PRES SLIPS SOUTH OF NEW ENGLAND. STRONGEST WINDS NORTHERN WATERS AND NEAR SHORE. VSBY MAY LOWER AT TIMES IN PERIODS OF RAIN. SATURDAY...LOW PRES MOVING ACROSS EASTERN QUEBEC INTO NEW BRUNSWICK WILL YIELD A MODEST WSW WIND ACROSS THE WATERS. COLD FRONTAL PASSAGE LATE SAT YIELDS A WIND SHIFT TO THE WNW WITH MODEST WIND GUSTS. SUNDAY...DIMINISHING WIND AND SEAS AS HIGH PRES CREST OVER NEW ENGLAND AND NEARBY COASTAL WATERS. DRY WEATHER RESULTS IN GOOD VSBY. && .FIRE WEATHER... 2 PM UPDATE... NOTED ERROR ON DEWPT AT MARTHAS VINEYARD DUE TO PROBLEMS WITH THE DEWPT SENSOR AT THE AIRPORT. BACKUP DEWPT SENSOR REPRESENTATIVE OF REGION...REPORTING 27 DEGREES AT 18Z. DEWPTS HAVE ACTUALLY RISEN ACROSS SE MA AS WINDS HAVE SHIFTED TO E-NE THROUGH MIDDAY. ELSEWHERE...DEWPTS REMAIN IN THE TEENS TO LOWER 20S WITH RH VALUES REMAINING IN THE 15-20 PERCENT. GUSTY N-NW WINDS BRIEFLY KICKED ON ACROSS THE CT VALLEY INTO N CENTRAL MA...BUT APPEAR TO BE DIMINISHING AFTER 17Z. RED FLAG CONTINUES FOR MOST OF MASSACHUSETTS THROUGH THE AFTERNOON...NOTING SOME BRUSH FIRE REPORTS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...RED FLAG WARNING UNTIL 7 PM EDT THIS EVENING FOR MAZ002>023- 026. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/SIPPRELL NEAR TERM...EVT SHORT TERM...SIPPRELL LONG TERM...NOCERA AVIATION...SIPPRELL/EVT MARINE...NOCERA/SIPPRELL/EVT FIRE WEATHER...STAFF

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