Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 300636 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 236 AM EDT SAT AUG 30 2014 .SYNOPSIS... HIGH PRESSURE OVER NEW ENGLAND MOVES OFFSHORE TODAY. WARMER MORE HUMID AIR WILL THEN MOVE UP FROM THE SOUTH AND SOUTHWEST WITH SUMMERTIME HUMIDITY STARTING SUNDAY. A COLD FRONT OVER THE PLAINS WILL STRUGGLE TO MOVE EAST...TAKING UNTIL TUESDAY NIGHT OR WEDNESDAY TO MOVE THROUGH NEW ENGLAND. DRY AND SEASONABLE WEATHER IS EXPECTED BEHIND THE FRONT FOR THE LATTER PART OF NEXT WEEK. && .NEAR TERM /THROUGH TODAY/... THROUGH 8 AM... A FEW PATCHES OF CLOUDS BUT MOSTLY CLEAR SKIES OVER SOUTHERN NEW ENGLAND. OTHERWISE CLEAR SKIES AND LIGHT WINDS ARE IN PLACE AND SHOULD CONTINUE FOR MOST OF THE NIGHT. THESE CONDITIONS SUPPORT RADIATIONAL COOLING. SURFACE TEMPS AT 1 AM WERE APPROACHING DEW POINT AT SEVERAL SPOTS SUCH AS TAN AND ORE. WE EXPECT AREAS OF RADIATION FOG TO DEVELOP OVERNIGHT ESPECIALLY IN THE COLDER VALLEY OF THE INTERIOR AND IN SOME OF THE LOW SPOTS OF EASTERN MASS. LOCAL VSBYS BELOW 1/2 MILE POSSIBLE. MIN TEMPS WILL BE GUIDED BY DEW POINT VALUES...IN THE UPPER 40S AND 50S. TODAY... GENERAL SUBSIDENCE UNDER THE HIGH SHOULD PROVIDE A SUNNY DAY. A MOIST LAYER WITH 75 PERCENT RH WILL LINGER BETWEEN 850 AND 900 MB WITH MIXING EXPECTED TO REACH TO 900 MB OR A LITTLE ABOVE. THIS SHOULD AGAIN GENERATE DIURNAL CUMULUS LATER THIS MORNING AND AFTERNOON. TEMPS AT THE TOP OF THE LAYER WILL SUPPORT MAX SFC TEMPS OF 73 TO 79F...A FEW SPOTS MAY TOUCH 80F. SOUTH WINDS COMING OFF THE OCEAN WILL KEEP THE SOUTH COAST A LITTLE COOLER...70 TO 75F. WINDS IN THE MIXED LAYER WILL BE AROUND 15-18 KNOTS...SO EXPECT SOME GUSTS TO THIS RANGE. && .SHORT TERM /TONIGHT THROUGH 6 PM SUNDAY/... TONIGHT... WITH HIGH PRESSURE OFFSHORE...SOUTH WINDS WILL BRING WARMER MORE HUMID AIR TOWARD NEW ENGLAND. THIS WILL MEAN INCREASING CLOUDS AS THE HIGHER HUMIDITY AIR RIDES UP OVER THE COOLER AIRMASS AT THE SURFACE. THE MOIST LAYER WILL BE CONCENTRATED BELOW 950 MB WITH AT BEST WEAK LIFT...SO EXPECT CLOUDS AND FOG WITH SOME DRIZZLE POSSIBLE. SUNDAY... SHORTWAVE MOVING THROUGH THE UPPER FLOW WILL START THE DAY OVER THE GREAT LAKES. AN 85-90 KNOT JET WILL DRIVE THE SYSTEM EAST INTO NEW ENGLAND BY LATER IN THE DAY. THE DYNAMICLY FAVORABLE ZONES FOR LIFT ASSOCIATED WITH THE JET WILL BE WELL TO OUR WEST IN THE MORNING...BUT THEN SHIFT INTO OUR AREA DURING THE AFTERNOON WITH THE BEST SUPPORT IN WESTERN MASS/SOUTHERN NH LATE IN THE DAY. CLOUDS MAY THIN IN THE MORNING BUT SHOULD THICKEN AGAIN THROUGH THE DAY AS SHORTWAVE AND ITS DEEPER MOISTURE MOVE IN. LAPSE RATE IN THE 850-500 MB LAYER IS SO-SO AT 5.5C/KM. TOTALS CLIMB TO THE MID 40S. WINDS AT 850 MB REACH 30 KNOTS WHILE 500 MB WINDS REACH 40-45 KNOTS. PRECIPITABLE WATER VALUES WILL CLIMB THROUGH THE DAY WITH AFTERNOON VALUES OF 2.0 TO 2.25 INCHES...MOVE THAN 2 STD DEVIATIONS ABOVE NORMAL AND POTENTIALLY NEAR 3. THIS FAVORS SHOWERS AND SCATTERED THUNDERSTORMS WITH POTENTIAL FOR STRONG WIND GUSTS AND HEAVY DOWNPOURS. && .LONG TERM /SUNDAY NIGHT 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 NIGHT INTO MONDAY... 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 /06Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT-TERM /THROUGH SUNDAY/...HIGH CONFIDENCE. TODAY...GENERALLY VFR. MVFR/IFR CIGS/VSBYS IN PATCHY FOG THROUGH SUNRISE ESPECIALLY IN PARTS OF THE CT VALLEY AND FAVORED SHELTERED SPOTS. LIGHT WINDS WILL INCREASING A LITTLE OUT OF THE SOUTH. TONIGHT...VFR EARLY. INCREASING RISK OF MVFR CIGS/VSBY IN DEVELOPING CLOUD COVER AND FOG/DRIZZLE...MAINLY AFTER MIDNIGHT. SUNDAY... MVFR/IFR EARLY IN FOG AND LOW CLOUDS. VSBY SHOULD IMPROVE TO VFR DURING THE MORNING EXCEPT ALONG THE SOUTH COAST WHERE IFR MAY LINGER. MVFR AND LOW-END VFR CEILINGS AWAY FROM THE SOUTH COAST DURING THE AFTERNOON. THUNDERSTORMS EXPECTED TO DEVELOP IN THE AFTERNOON...MOSTLY IN THE CT VALLEY AND SOUTHERN NH. POTENTIAL FOR HEAVY DOWNPOURS AND STRONG WIND GUSTS WITH ANY THUNDERSTORMS. KBOS TERMINAL...HIGH CONFIDENCE IN TAF. KBDL TERMINAL...HIGH CONFIDENCE IN TAF. OUTLOOK...SUNDAY NIGHT THROUGH WEDNESDAY... SUNDAY NIGHT 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...WTB/SIPPRELL NEAR TERM...WTB SHORT TERM...WTB LONG TERM...SIPPRELL AVIATION...WTB/SIPPRELL MARINE...NOCERA/SIPPRELL

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