Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 292320 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 720 PM EDT FRI AUG 29 2014 .SYNOPSIS... HIGH PRESSURE OVER NEW ENGLAND WILL PROVIDE DRY AND COOL WEATHER THROUGH SATURDAY MORNING. TEMPERATURES WILL BEGIN TO MODERATE SATURDAY AFTERNOON AS THE HIGH DRIFTS OFFSHORE. BY SUNDAY VERY WARM AND HUMID CONDITIONS OVERSPREAD THE AREA AS A COLD FRONT APPROACHES THE REGION FROM THE WEST. THIS MAY RESULT IN FEW THUNDERSTORMS LATER SUNDAY INTO MONDAY AND POSSIBLY TUESDAY. DRY AND SEASONABLE WEATHER IS EXPECTED BEHIND THE FRONT FOR THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 730 PM UPDATE... AS HIGH PRESSURE SHIFTS E ALLOWING FOR RETURN S-FLOW...SOME HINT AT INCREASING HUMIDITY AT THE H975-FIELD ACROSS THE S-COAST SUCH THAT LOW CLOUDS MAY BE AN ISSUE TOWARDS MORNING. OTHERWISE... NOTING DEWPOINTS AT MAX-HEATING OF THE DAY IN THE LOW- TO MID-50S AND CONSIDERING CONDITIONS THIS EVENING WHICH MAY ALLOW GOOD RADIATIONAL COOLING...PATCHY DENSE FOG IS POSSIBLE...FOCUSED OVER THE CT- AND MERRIMACK-RIVER VALLEYS...AS WELL AS THE S/SE INTERIOR IMMEDIATELY AWAY FROM THE S-COAST /I.E. E CT AND W RI...SE MA/. FORECAST LOWS DOWN AROUND THE LOW- TO MID-50S WITH A FEW AREAS IN THE UPPER-40S. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... SATURDAY... REAL NICE DAY ONCE EARLY MORNING PATCHY FOG/LOW CLOUDS BURN OFF. MID LEVEL RIDGE AXIS IS CENTERED OVER THE AREA YIELDING ANTICYCLONIC FLOW PROVIDING DRY WEATHER AND A FAIR AMOUNT OF SUNSHINE. LIKELY TO SEE TODAY/S MOISTURE REMAIN TRAPPED BENEATH SUBSIDENCE INVERSION SO ANOTHER ROUND OF SCT-BKN STRATO-CU EXPECTED. AS LOW LEVEL WINDS BECOME SSW AIRMASS WILL MODIFY SOMEWHAT WITH HIGHS TOMORROW IN THE MU 70S EXCEPT L70S ALONG THE SOUTH COAST GIVEN THE ONSHORE WINDS. SATURDAY NIGHT... WARM FRONT MOVES ACROSS THE AREA SO EXPECT MORE HUMID CONDITIONS WITH DEW PTS CLIMBING INTO THE 60S. CROSS SECTIONS SUGGEST MOISTURE IS FAIRLY SHALLOW SO NOT EXPECTING MUCH PRECIP OTHER THAN POSSIBLY AREAS OF DRIZZLE. THUS LOW CLOUDS WILL BE ON THE INCREASE. THE CLOUD COVER AND HIGHER DEW PTS WILL RESULT IN WARMER CONDITIONS THAN PREVIOUS NIGHTS ALONG WITH PATCHY FOG. && .LONG TERM /SUNDAY THROUGH FRIDAY/... */ HIGHLIGHTS... - PROLONGED PERIOD OF SHOWERS AND THUNDERSTORMS SUNDAY INTO MONDAY - COLD FRONT SWEEPS NEW ENGLAND AROUND TUESDAY - DRY AND QUIET WEATHER FOR THE REMAINDER OF THE WEEK */ OVERVIEW AND MODEL PREFERENCE... CONTINUED PREFERENCE OF SEASONABLE TO ABOVE AVERAGE TEMPERATURES ASSOCIATED WITH WEAK RIDGING OF A ZONAL-FLOW PATTERN INTO EARLY SEPTEMBER SIGNALED BY A NEGATIVE TO NEAR-NEUTRAL NAO / PNA. WITH LESSER MAGNITUDE OF WIND THROUGH ALL LEVELS EMPHASIZED BY ENSEMBLES NOT EXPECTING ROBUST-AMPLIFIED SYSTEMS...RATHER A SUBDUED WEATHER- PATTERN. ANTICIPATE IMPULSES THROUGH THE ZONAL- FLOW REGIME WITH THE BULK OF ACTIVITY EDGED N BY WEAK RIDGING / HIGHER HEIGHTS...THOUGH TRAILING OVER THE NE-CONUS TO ALLOW PERIODS OF DISTURBED WEATHER /THINKING MAINLY SUB-SEVERE/ AND BRIEF-SHOTS OF REFRESHING AIR. STILL FAVOR THE ECMWF / ECENS WITH DECENT RUN-TO-RUN CONSISTENCY. FEEL THE GFS IS CLOSE TO FOLLOWING SUIT. DO NOT FAVOR THE 29.12Z NAM AFTER 0Z MONDAY. HIGHLIGHTS/CONFIDENCE ARE BROKEN DOWN IN THE DAILY DISCUSSION BELOW. */ DAY-TO-DAY DETAILS... SUNDAY INTO MONDAY... WOULD EXPECT SCATTERED SHOWERS WITH DAYTIME-INSTANCES OF THUNDER- STORMS AS A WEAK DISTURBANCE SLIDES ACROSS THE REGION. BULK-FORCING PER POSITIVE VORTICITY ADVECTION WITHIN A MID-LEVEL CONDITIONALLY UNSTABLE PROFILE /H85-7/ ABOVE A LOW-LEVEL MOIST-UNSTABLE AXIS SHOULD ALLOW FOR FAVORABLE ASCENT...STRONGEST OF WHICH DURING THE DAY WITH WELL-MIXED BOUNDARY-LAYER PROFILES / POSITIVE BUOYANCY. DIFFICULT TO NAIL DOWN EXACTLY WHERE AND WHEN ACTIVITY WILL DEVELOP. THINKING INITIAL ACTIVITY ON SUNDAY WILL BE ACROSS THE N/W INTERIOR CLOSER TO BULK-FORCING AND ALONG THE S/W-SLOPES OF HIGHER TERRAIN WITH OROGRAPHIC LIFT...WHEREVER ASCENT IS POSSIBLE AS THE CONVECTIVE- TEMPERATURE IS MET TO BREAK THE CAP OF A LINGERING DRY-SUBSIDENCE INVERSION. WITH 0-6 KM BULK SHEAR /AROUND 30 KTS/ AND FREEZING-LEVEL HEIGHTS OF AROUND 14-15 KFT...EXPECT ONLY A FEW STRONG STORMS. VERY LITTLE IN THE WAY OF JET DYNAMICS. WILL ONLY ENTERTAIN THE THREAT OF HEAVY RAIN WITH PWATS EXCEEDING 2-INCHES...THOUGH ISOLATED AS DEEP- LAYER FORCING IS LACKING. ORDINARY TO MULTICELLUR STORMS CONSIDERED BASED ON CONVECTIVE INDICES. WARM AND MUGGY WITH BREEZY S/SW WINDS. ACTIVITY DIMINISHES SUNDAY EVENING AND OVERNIGHT WITH THE CONCLUSION OF DAYTIME-HEATING AND AS ENERGY STRETCHES TO THE NE OF THE DOMINANT W-ATLANTIC RIDGE. SHOWERS STILL ANTICIPATED WITH MID-LEVEL MOIST- CONVERGENCE AND ASCENT WITHIN A CONTINUED CONDITIONALLY UNSTABLE PROFILE SLIDING SE TOWARDS THE WATERS. NOT AS CONVINCED AS EARLIER THAT THERE WILL BE A LOT OF ACTIVITY ON MONDAY. COULD BE AN ISOLATED SHOW WHERE FORCING IS PRESENT WITHIN A LINGERING MOIST-UNSTABLE PROFILE. ITS LIKELY WHEREVER THE CONVECTIVE TEMPERATURE CAN BE MET WILL SHOWERS AND THUNDERSTORMS GENERATE. FEEL BULK OF ENERGY SHIFTING S/E AND UNDERGOING STRETCHING THROUGH THE ZONAL-FLOW WILL RESULT IN WEAKER DYNAMICS. ACTIVITY CONCLUDES INTO THE NIGHTTIME HOURS WITH ACTIVITY E. SHOULD TURN QUIET. TUESDAY INTO WEDNESDAY... CONSIDERING THE FOLLOWING: EARLY-WEEK ENERGY IS STRETCHED OFFSHORE ALONG THE W-PERIPHERY OF THE W-ATLANTIC RIDGE. COLD FRONT PUSHES IN FROM THE W WITH PARENT DYNAMICS SHIFTING NW WELL INTO CANADA. A LOW- LEVEL MOIST-UNSTABLE PLUME RE-SURGES INTO THE NE-CONUS COLLOCATED WITH AN ENVIRONMENT OF DECENT MID-LEVEL LAPSE RATES. RIDGING STILL PREVAILS OVER THE REGION. WHILE SOME SCATTERED SHOWER / THUNDERSTORM ACTIVITY IS POSSIBLE... FEEL IT WILL BE CONFINED TO THE N / W INTERIOR. SE MAY FIND ITSELF BENEATH SUBSIDENCE BETWEEN THE TWO SYSTEMS MENTIONED ABOVE. BEST CHANCE IS DURING THE DAY TUESDAY WITHIN DECENT INSTABILITY AND SOME SHEAR AROUND 15-20 KTS. DYNAMICS LACKING AND WEAK RIDGING IS STILL IN PLACE. THURSDAY INTO FRIDAY... WILL PREVAIL WITH THE ECMWF OF ZONAL-FLOW AND HIGHER HEIGHTS. HIGH PRESSURE IN CONTROL. SEASONABLE CONDITIONS WITH SOME COOL NIGHTS. NEXT WEEKEND... ANOTHER COLD FRONT POTENTIALLY SLIDES ACROSS THE REGION...STRETCHING AND BECOMING DIFFUSE AS IT PROGRESSES SE TOWARDS A W-ATLANTIC RIDGE PATTERN. && .AVIATION /23Z FRIDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH SATURDAY NIGHT/...HIGH CONFIDENCE. MOSTLY VFR. MVFR-IFR CIGS AND VSBYS DUE TO PATCHY FOG POSSIBLE FOR CT- AND MERRIMACK-VALLEY TERMINALS...AS WELL AS IMMEDIATE INTERIOR LOCALES AWAY FROM THE SHORE /I.E. E CT AND W RI...AND SE MA/. PATCHY IN COVERAGE...WILL ERODE WITH SUNRISE. LIGHT AND VARIABLE WINDS. SATURDAY...MARGINAL MVFR-VFR IN SCT-BKN035-045 DURING THE AFTERNOON HOURS. LOW RISK OF MORE WIDESPREAD MVFR CIGS BKN020-030 ACROSS RI AND SOUTHEAST MA. SE WINDS BECOMING MORE S IN THE AFTERNOON. DRY WEATHER/RUNWAYS CONTINUE. SAT NIGHT...INCREASING RISK OF MVFR CIGS AND VSBYS. SHOULD REMAIN DRY. S WINDS BECOME MORE SSW DURING THE NIGHT. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...SUNDAY THROUGH WEDNESDAY... SUNDAY INTO MONDAY...MODERATE CONFIDENCE. SHRA THROUGHOUT THE PERIOD WITH DAYTIME-INSTANCES OF TSRA. BREEZY S- WINDS. MIX OF LOW-END VFR TO MVFR...POSSIBLE IFR ALONG THE S-COAST SUNDAY AND MONDAY MORNING PRIOR TO ACTIVITY PUSHING OFFSHORE TOWARDS TUESDAY MORNING. TUESDAY...MODERATE CONFIDENCE. COLD FRONT WITH SOME SHRA/TSRA FOR N/W NEW ENGLAND. LOWER CONFIDENCE S/E. LOW-END VFR CIGS WITH WET-WEATHER. WEDNESDAY...MODERATE CONFIDENCE. VFR. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. TONIGHT... PLEASANT BOATING WEATHER WITH LIGHT WINDS AND DIMINISHING SE SWELL. VSBY MAY LOWER IN FOG TOWARD MORNING NEAR SHORE. SATURDAY...OTHER THAN SOME PATCHY MORNING FOG NEAR SHORE EXPECT GOOD VSBY AND DRY WEATHER. HIGH PRES BEGINS TO SLIDE OFFSHORE SO WINDS BECOME SSW. SAT NIGHT...WARM FRONT MOVES ACROSS THE WATERS SO PATCHY FOG AND DRIZZLE POSSIBLE. A MODEST SSW WIND EXPECTED. OUTLOOK...SUNDAY THROUGH WEDNESDAY... SUNDAY INTO MONDAY...MODERATE CONFIDENCE. BREEZY S/SW-WINDS WITH GUSTS UP TO 25 KTS. WAVE HEIGHTS IN EXCESS OF 5-FEET ACROSS THE S/SE WATERS. SHOWERS ENCROACHING UPON THE WATERS LATE SUNDAY AND CONTINUING THROUGH TUESDAY MORNING. FOG POSSIBLE DURING THE OVERNIGHT HOURS ALONG THE S-COAST THOUGH LOW CONFIDENCE. TUESDAY INTO WEDNESDAY...MODERATE CONFIDENCE. COLD FRONT SWEEPS ACROSS THE WATERS...BUT EXPECTING JUST A FEW SHOWERS...MAINLY DRY. WAVE HEIGHTS BELOW 5-FEET. WINDS REMAINING BELOW 25 KTS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...NOCERA/SIPPRELL NEAR TERM...NOCERA/SIPPRELL SHORT TERM...NOCERA LONG TERM...SIPPRELL AVIATION...NOCERA/SIPPRELL MARINE...NOCERA/SIPPRELL

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