Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 160158 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 958 PM EDT MON SEP 15 2014 .SYNOPSIS... A COLD FRONT WILL SWEEP SOUTHERN NEW ENGLAND BRINGING WITH THE CHANCE OF SCATTERED SHOWERS BEGINNING AFTER MIDNIGHT TONIGHT THROUGH TUESDAY. MAINLY DRY BUT COOLER THAN NORMAL WEATHER FOLLOWS WEDNESDAY THROUGH SATURDAY. TEMPERATURES THEN MODERATE TO NEAR NORMAL BY THE END OF THE WEEKEND. && .NEAR TERM /THROUGH TUESDAY/... 10 PM UPDATE... NO MAJOR ADJUSTMENTS WITH THIS UPDATE EITHER. PRIMARY CHANGES WERE TO INCREASE CLOUD COVER ACROSS THE AREA AS HIGH CLOUDS ARE ALREADY SPILLING INTO THE REGION FROM THE W. WITH THIS IN MIND ALSO...HAVE INCREASED BOTH HOURLY AND MIN TEMPS AS WELL AS DWPTS A BIT WITH THIS UPDATE. THE INCREASED CLOUD COVER AND SLIGHT UP- TICK IN DWPTS IS LIKELY TO MITIGATE COOLING TONIGHT IN COMPARISON TO PREVIOUS COOLER NIGHTS. OTHERWISE...FORECAST ON TRACK...INCLUDING POPS TOWARD DAYBREAK. INTO TONIGHT... A FALL-LIKE CHILL REMAINS IN THE AIR AS SCATTERED TO BROKEN PANCAKE CUMULUS LINGER ACROSS THE SKY. SHOULD SEE PRESENT HIGH TEMPERATURES AROUND THE UPPER-60S DROP TOWARDS THE LOWER-60S BY SUNDOWN. TONIGHT INTO TUESDAY... A MODEST MID-LEVEL IMPULSE WILL INVOKE WEAK TROUGHING AS IT ROUNDS THE BASE OF A DEEPER-LOW OVER THE NE-CANADIAN MARITIMES. CONSIDERING LOW-LEVEL CONVERGENCE OF A CONTINENTAL-MOIST AIRMASS UNDERGOING MID- LEVEL ENHANCED ASCENT COLLOCATED WITH A REGION OF FRONTOGENETICAL FORCING AND RIGHT-ENTRANCE-REGION OF THE UPPER-LEVEL JET /WHEW/... WOULD EXPECT SCATTERED LIGHT TO MODERATE SHOWER ACTIVITY ALONG A LINE AHEAD OF THE SURFACE COLD FRONT. THE LATEST HRRR IS SHOWING SUCH A TREND FAIRLY WELL ACROSS THE E GREAT LAKES BY MIDNIGHT TUESDAY. BUT A FEW THINGS WORTHY OF NOTE...NOT AN IMPRESSIVELY MOIST-AIRMASS WITH PWATS OF 1.00-1.25 INCHES. SUBSIDENCE AND DRY AIR CONTINUE TO PREVAIL SE...SQUEEZED BETWEEN THE APPROACHING MID-LEVEL IMPULSE AND WELL-OFFSHORE SUBTROPICAL AXIS BUCKLED BY THE MEANDERING HURRICANE EDOUARD. ANOMALOUSLY COOLER FOR THIS TIME OF YEAR OVER MUCH OF THE REGION...LOW CONFIDENCE CONCERNING THUNDER AND INSTABILITY. SO WILL NOT GO WITH A MENTION OF THUNDER. NOT EXPECTING A WASHOUT. WILL KEEP THE HIGHEST CATEGORICAL POPS TOWARDS THE W ESPECIALLY ALONG THE SLOPES OF HIGHER TERRAIN. WILL TAPER TO CHANCE POPS OFF TOWARDS THE SE AS ACCOMPANYING DYNAMICS TO THE DISTURBANCE SHIFT TO THE NE SHUNTING THE SURFACE COLD FRONT INTO A REGION OF SUBSIDENCE AND DRIER AIR. ELSEWHERE...EXPECTING AROUND A TENTH FOR AREAS OF W NEW ENGLAND...WITH A FEW HUNDREDTHS ACROSS CENTRAL AND E. MANY NOT SEE ANY PRECIPITATION WHATSOEVER FOR E/SE MASSACHUSETTS. && .SHORT TERM /TUESDAY NIGHT/... TUESDAY NIGHT... COLD FRONT PUSHING OFFSHORE. SOME BREEZY N/NW-FLOW REARWARD IS CERTAINLY PLAUSIBLE INITIALLY...BUT HIGH PRESSURE QUICKLY FOLLOWS ALLOWING WINDS TO RELAX. THOUGH THE POSSIBILITY OF SOME MID-LEVEL SCATTERED CLOUD DECKS WILL EXIST...THERE IS ALSO THE POTENTIAL OF EFFECTIVE RADIATIONAL COOLING OVERNIGHT WHICH WOULD LIKELY RESULT IN ABNORMAL LOWS INTO THE 40S ALONG WITH AREAS OF DENSE FOG...ESPECIALLY FOR THOSE REGIONS THAT RECEIVED A MODEST RAIN OVER THE PAST 24 HOURS /THINKING THE WEST- AND CENTRAL-INTERIOR...ESPECIALLY THE MID-CT RIVER VALLEY/. LOWS INTO THE 40S WITH THE POTENTIAL FOR UPPER-30S ACROSS THE HIGH TERRAIN OF N/W MASSACHUSETTS AND S NEW HAMPSHIRE. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... HIGHLIGHTS... * MAINLY DRY AND COOLER THAN NORMAL WEATHER THROUGH SATURDAY * TEMPERATURES MODERATE GOING INTO THE WEEKEND * A COLD FRONT BRINGS SOME RAIN TO THE REGION SUNDAY INTO MONDAY MODELS...INCLUDING ENSEMBLES...ARE IN GOOD AGREEMENT THROUGH MUCH OF THE LONG TERM WITH ONLY SOME MINOR DETAIL DIFFERENCES. THEREFORE... WILL USE A BLEND OF AVAILABLE GUIDANCE FOR MUCH OF THE FORECAST. POINTS OF INTEREST INCLUDE THE POTENTIAL FOR COLD TEMPERATURES AND FROST FOR THURSDAY NIGHT INTO FRIDAY AND A COLD FRONT BRINGING RAIN TO THE REGION SUNDAY INTO MONDAY. WEDNESDAY AND THURSDAY...A BROAD UPPER TROUGH OVER THE NORTHEAST US WILL SLOWLY MOVE OFFSHORE DURING THIS TIME. HIGH PRESSURE BUILDS OVER SOUTHERN NEW ENGLAND BRINGING AND SLIGHTLY COOLER THAN NORMAL TEMPERATURES AND DRY WEATHER TO THE REGION. FRIDAY...THIS IS THE COOLEST DAY BY FAR WITH LOW TEMPERATURES FRIDAY MORNING EXPECTED TO BE IN THE LOW TO MID 30S ACROSS PORTIONS OF THE FAR INTERIOR AND IN THE UPPER 40S ALONG THE COAST. HIGH TEMPERATURES WILL THEN BE A GOOD 10 TO 15 DEGREES BELOW NORMAL. OTHER THAN THE TEMPERATURES...EXPECT A PLEASANT DAY WITH MOSTLY CLEAR SKIES AS HIGH PRESSURE REMAINS OVER THE REGION. SATURDAY THROUGH MONDAY...TEMPERATURES START TO MODERATE THROUGH THE WEEKEND WITH WARMING SOUTHERLY SURFACE WINDS IN PLACE AHEAD OF A COLD FRONT STEMMING FROM AN INTENSIFYING AREA OF LOW PRESSURE JUST NORTH OF THE GREAT LAKES. THIS IS ASSOCIATED WITH A DEEP UPPER LEVEL TROUGH OVER THE GREAT LAKES THAT WILL SLOWLY MOVE OVER SOUTHERN NEW ENGLAND AND THEN OFFSHORE BY EARLY NEXT WEEK. EXPECT SOME RAINFALL AHEAD OF THE COLD FRONT SUNDAY AND MONDAY. MODELS ARE INDICATING SOME INSTABILITY SO THUNDER IS A POSSIBILITY AT THIS POINT...BUT WILL LEAVE IT OUT SINCE MUCH COULD CHANGE IN THE NEXT WEEK. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM FORECAST /THROUGH TUESDAY NIGHT/...HIGH CONFIDENCE. TONIGHT...SHRA AFTER MIDNIGHT FOR W-TERMINALS DISSIPATING AS THEY SPREAD E. WILL HOLD WITH LOW-END VFR CIGS WITH ONLY PERHAPS MVFR FOR S-COASTAL TERMINALS. WINDS TURNING S. TUESDAY...SHRA DISSIPATING AS SW-WINDS SHIFT OUT OF THE W-NW WITH THE COLD FRONTAL PASSAGE. LOW-END VFR CIGS OVERALL WITH PERHAPS SOME MVFR LINGERING ALONG THE S-COAST DURING THE MORNING. TUESDAY NIGHT...VFR WITH WINDS BECOMING VRB. DENSE FOG POSSIBLE FOR THE W-INTERIOR TERMINALS...ESPECIALLY THE CT-VALLEY FROM KBAF NORTHWARD. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...WEDNESDAY THROUGH FRIDAY. WEDNESDAY THROUGH FRIDAY...HIGH CONFIDENCE. VFR. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM FORECAST /THROUGH TUESDAY NIGHT/...MODERATE CONFIDENCE. WHILE THE WEATHER WILL BE FOR THE MOST PART QUIET WITH A DRY COLD FRONTAL PASSAGE EXPECTED FOR LATE TUESDAY /WINDS OUT OF THE SW SHIFTING OUT OF THE W-NW/...MAIN CONCERN IS THE ANTICIPATED SWELL AND WAVES ASSOCIATED WITH EDOUARD. WITH EDOUARD FAR REMOVED FROM THE COAST...AND OVERDONE FORECAST MODELS WITH REGARDS TO SEAS...HAVE HELD WAVE HEIGHTS NO GREATER THAN 5 FEET. HAVE ALSO HELD OFF ON THE ISSUANCE OF SMALL-CRAFT ADVISORIES FOR SEAS. WILL RE-EVALUATE AS WE GET CLOSER TO THE POTENTIAL FOR SIGNIFICANT WAVE HEIGHTS AND POSSIBLE RIP CURRENT THREAT BEGINNING TUESDAY NIGHT TOWARDS WEDNESDAY. OUTLOOK...WEDNESDAY THROUGH SATURDAY... WEDNESDAY THROUGH FRIDAY...LINGERING SWELL FROM HURRICANE EDOUARD /KEEPS WELL OUT TO SEA/ KEEPS SEAS IN THE 5 TO 6 FOOT RANGE ON THE OUTER WATERS. WINDS WILL REMAIN FAIRLY LIGHT AND VARIABLE THROUGH THURSDAY WITH HIGH PRESSURE OVER THE WATERS. NORTHEASTERLY WINDS MAY GUST TO NEAR 25 KTS FRIDAY AFTERNOON AS THE HIGH SHIFTS EASTWARD. LATE FRIDAY NIGHT INTO SATURDAY...QUIET BOATING WEATHER EXPECTED. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...RLG/SIPPRELL NEAR TERM...DOODY/SIPPRELL SHORT TERM...SIPPRELL LONG TERM...RLG AVIATION...RLG/SIPPRELL MARINE...RLG/SIPPRELL

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