Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 020146 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 945 PM EDT FRI AUG 1 2014 .SYNOPSIS... SCATTERED SHOWERS AND THUNDERSTORMS SHOULD DIMINISH EARLY THIS EVENING. A SERIES OF LOW PRESSURE AREAS MOVING ALONG A STALLED FRONT WILL LIKELY BRING PERIODS OF RAIN TO AT LEAST SOUTHEAST NEW ENGLAND ON SATURDAY AND SUNDAY. UNSETTLED WEATHER REMAINS WITH US MUCH OF THE WEEK AS A COUPLE OF COLD FRONTS MOVE THROUGH. && .NEAR TERM /UNTIL NOON SATURDAY MORNING/... 945 PM UPDATE... ***SATURDAY WASHOUT EXPECTED FOR EASTERN NEW ENGLAND*** CONVECTION FROM THIS AFTERNOON AND EARLY EVENING HAS COME TO AN END AS INSTABILITY WAS WANING. DRY WEATHER EXPECTED THE REST OF THE EVENING. ALL ATTENTION NOW TURNS TO PLUME OF TROPICAL MOISTURE STREAMING NORTHWARD OFF THE MID ATLANTIC COAST. BASED ON SOME SHORT TERM AND 18Z GUIDANCE...HAVE EXPANDED CATEGORICAL POPS FOR SATURDAY INTO MUCH OF EASTERN NEW ENGLAND. ALSO...INCREASED POPS SOME ACROSS THE INTERIOR. THIS STILL MAY NOT BE ENOUGH...BUT WANTED TO TREND IN THE RIGHT DIRECTION. APPEARS STEADY RAIN WILL BEGIN TO WORK NORTHWARD INTO MUCH OF THE REGION BY 12Z. BANDS OF HEAVY RAIN ARE EXPECTED ACROSS EASTERN NEW ENGLAND ON SATURDAY GIVEN PWATS APPROACHING 2 INCHES. THIS MAY RESULT IN TYPICAL NUISANCE POOR DRAINAGE STREET FLOODING...BUT DO NOT SEE ANY MAJOR PROBLEMS AT THIS TIME. MARGINAL INSTABILITY MAY RESULT IN AN ISOLATED THUNDERSTORM OR TWO ACROSS THE SOUTHEAST NEW ENGLAND COAST...BUT MAIN STORY WILL BE BANDS OF HEAVY RAIN AND SATURDAY WASHOUT FOR MUCH OF EASTERN NEW ENGLAND. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... ***A PERIOD OF STEADY AND POSSIBLY HEAVY RAIN LIKELY ON SATURDAY FOR AT LEAST EASTERN NEW ENGLAND*** WATER VAPOR IMAGERY DEPICTS RATHER IMPRESSIVE TROPICAL CONNECTION ALONG THE EASTERN SEA BOARD AHEAD OF OH VALLEY TROF. MODELS ALL DEPICT IN SOME WAY SHAPE OR FORM A WEAK LOW PRESSURE WAVE MOVING ALONG A STALLED FRONTAL BOUNDARY JUST OFFSHORE. PWATS INCREASE FROM A LITTLE OVER 1 INCH THIS AFTERNOON TO 1.5 TO 2 INCHES ACROSS MUCH OF SOUTHERN NEW ENGLAND BY SATURDAY AFTERNOON. NOTED THAT THE 12Z ECMWF WAS ESPECIALLY BULLISH WITH THE RAINFALL PROJECTION AND ALSO STRONGER WITH THE SATURDAY LOW PRESSURE WAVE ALONG THE BOUNDARY. THE NAM SEEMED TO BE MORE INCLINED TO PUT AS MUCH OR MORE ENERGY IN A SECOND WAVE LATER IN THE WEEKEND. THE SREF OUTPUT DEPICTS LESS THAN 20 PERCENT CHANCE OF AN INCH OR MORE RAIN SATURDAY BUT THE SREF IS MADE UP OF A NUMBER OF NAM MEMBERS. IN SPITE OF SOME MODEL DIFFERENCES...SEE ENOUGH INDICATORS TO GO WITH CATEGORICAL POPS ACROSS SE MA AND SOUTHERN RI AND LIKELY POPS AS FAR NORTH AND WEST AS NEWBURYPORT TO THE WORCESTER AREA TO NW HARTFORD COUNTY. INDICATED STRATIFORM RAIN IN THE LIKELY AND CATEGORICAL POP AREAS AND SHOWERY TO THE NW. THE WATER VAPORY IMAGERY...INCREASE IN PWATS...DEEP SYNOPTIC SCALE SW FLOW WITH A TROPICAL ORIGIN AND MODEL CONSENSUS LEADS TO BELIEVE A RELATIVELY HIGH CHANCE OF 1 TO 1.5 INCHES OF RAIN ACROSS THE SE HALF OF THE AREA AND TAPERING OFF TO QUITE A BIT LESS TO THE NW. THERE IS A LOW PROBABILITY OF EMBEDDED AND ELEVATED THUNDER ACROSS SOUTHEAST MA AND SOUTHERN RI WHERE K INDICES MAY REACH TO NEAR OR JUST ABOVE 30. TEMPERATURES ON SATURDAY ARE NOT LIKELY TO REBOUND VERY HIGH DUE TO CLOUDS AND RAIN IN MUCH OF THE AREA. WARMEST TEMPERATURES LIKELY IN THE KEENE AREA. MOST LOCATIONS WILL PROBABLY NOT RISE OUT OF THE LOWER OR MID 70S. SATURDAY NIGHT...HAVE TAPERED POPS DOWN AS SURFACE WAVE MOVES NE OUT OF AREA. DEPENDING UPON STRENGTH OF THE SURFACE WAVE OF LOW PRESSURE...MAY SEE BOUNDARY SHIFT A LITTLE FURTHER SE. HAVE POPS TAPERING OFF TO CHANCE MOST AREAS EXCEPT KEPT THEM LIKELY ACROSS THE CAPE AND ISLANDS CLOSER TO THE FRONTAL BOUNDARY. ANTICIPATE FEED OF TROPICAL MOISTURE WILL CONTINUE AND THE AIR MASS APPROACHES CONDITIONALLY UNSTABLE STATUS OVER THE CAPE AND ISLANDS. FOG MAY BE MORE WIDESPREAD LATE SATURDAY NIGHT DUE TO LIGHT WINDS AND ADDED MOISTURE FROM THE RAIN...ESPECIALLY ACROSS SE SECTIONS. LOW TEMPERATURES SATURDAY NIGHT WILL DEPEND TO SOME DEGREE UPON THE STRENGTH OF THE SURFACE WAVE AND WHETHER IT IS ABLE TO DRAW ANY DRIER AIR INTO SOUTHERN NEW ENGLAND. WOULD EXPECT CLOUDS TO PREVENT MUCH OF A DIURNAL DROP IN TEMPERATURES OVER THE SE HALF OF THE AREA. && .LONG TERM /SUNDAY THROUGH FRIDAY/... BIG PICTURE... UPPER TROUGH OVER THE EAST WITH UPPER RIDGE OVER THE WESTERN USA. ONE SHORTWAVE EJECTS FROM THE EASTERN TROUGH SUNDAY WHILE ANOTHER SHORTWAVE DROPS IN FROM CANADA. THE TROUGH THEN MIGRATES EAST THROUGH NEW ENGLAND WEDNESDAY THROUGH FRIDAY. THIS IS AN UNSETTLED PATTERN...BUT WITH NEAR SEASONABLE TEMPERATURES. THE DAILIES... SUNDAY... COLD FRONT REMAINS STALLED OFF THE SOUTH COAST. MEANWHILE THE UPPER SOUTHWEST JET REMAINS TO OUR WEST WITH SOUTHERN NEW ENGLAND UNDER THE RIGHT ENTRANCE REGION. THIS WILL SUPPORT UPPER VENTING OVER THE LOW LEVEL CONVERGENCE ALONG THE FRONT...RESULTING IN ONE OR MORE WAVES MOVING ALONG THE FRONT AND PRODUCING AREAS OF ISENTROPIC LIFT THAT MOVE UP ACROSS PARTS OF SOUTHERN NEW ENGLAND. THE MOST LIKELY LOCATION FOR LIFT AND RESULTING PRECIP WOULD BE ACROSS RI AND SOUTHEAST MASS. PRECIPITABLE WATER VALUES OF 1.5 TO 1.75 INCHES WITH 2 INCH VALUES JUST SOUTH OF THE COAST...SO POTENTIAL FOR A FEW HEAVY DOWNPOURS. WITH AN ILL-DEFINED SURFACE PATTERN AND THE UPPER JET RIGHT ENTRANCE REGION ALSO OVERHEAD...WITH COOLING TEMPS ALOFT AS THE UPPER SHORTWAVE EJECTS...AND WITH MID LEVEL LAPSE RATES AROUND 6C/KM AND TOTALS AROUND 48 TO OUR NORTHWEST...THERE IS ALSO POTENTIAL FOR AFTERNOON/EVENING TSTMS TO DEVELOP OVER NY AND VT. THESE COULD THEN MOVE INTO OUR WESTERN AND NORTHERN AREAS...BUT THE LESS FAVORABLE ENVIRONMENT HERE SHOULD CAUSE THAT CONVECTION TO DIMINISH. MODEL QPF FIELDS ALSO INDICATE MEASURABLE PCPN MOSTLY OUTSIDE OF OUR AREA BUT POTENTIALLY CLIPPING OUR NORTHWEST. TEMPS ALOFT AROUND 11C WOULD SUPPORT MAX SURFACE TEMPS AROUND 80F. CLOUDS IN THE EAST SHOULD KEEP TEMPS COOLER...WHILE INTERIOR SECTIONS MAY SEE ENOUGH SUN TO REALIZE THE WARMER MAX TEMPS. MONDAY-TUESDAY... INSTABILITY LINGERS NORTH AND WEST...AND ACROSS OUR NORTHERN/WESTERN ZONES. ON TUESDAY...A COLD FRONT APPROACHES FROM THE NORTHWEST. THIS SHOULD BE ENOUGH TO GENERATE AFTERNOON/EVENING TSTMS EACH DAY. WEDNESDAY THROUGH FRIDAY... THE COLD FRONT MOVES THROUGH NEW ENGLAND ON WEDNESDAY ALONG WITH THE COLDER TEMPS ALOFT. THIS SHOULD BRING A CHANCE OF SHOWERS/TSTMS. LINGERING INSTABILITY THURSDAY WITH THE UPPER TROUGH STILL IN THE NEIGHBORHOOD...BUT A DRIER AIRMASS. WILL INDICATE SLIGHT CHANCE POPS MOST PLACES AND CHANCE POPS MERRIMACK VALLEY. HIGH PRESSURE BUILDS IN PLACE FRIDAY WITH DRIER WEATHER. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT... TONIGHT...MODERATE TO HIGH CONFIDENCE. MAINLY VFR CONDITIONS EXCEPT AREAS OF IFR IN FOG ESPECIALLY IN AREAS THAT HAVE RECEIVED SIGNIFICANT RAINFALL. SATURDAY...MODERATE CONFIDENCE. EXPECT A PERIOD OF STEADY RAIN ALONG AND SE OF A LWM-ORH-BDL LINE WITH WIDESPREAD MVFR CIGS AND VSBYS DEVELOPING. GENERALLY VFR NW OF THIS LINE. AREAS OF IFR CIGS AND VSBYS POSSIBLE SE MA AND SOUTHERN HALF OF RI LATE MORNING INTO THE AFTERNOON. SATURDAY NIGHT...MODERATE CONFIDENCE. ANTICIPATING VFR CONDITIONS NW HALF OF AREA AND GENERALLY MVFR CIGS AND VSBYS SE HALF. AREAS OF FOG AND SCATTERED SHOWERS PERSISTING SE HALF OF AREA. KBOS TAF...HIGH CONFIDENCE IN GENERALLY VFR CONDITIONS THROUGH TONIGHT. MOST TSTM ACTIVITY IN THE EARLY EVENING SHOULD OCCUR NW OF THE AIRFIELD BUT A LOW PROBABILITY REMAINS OF ONE MAKING A CLOSE PASS TO THE AIR FIELD. SEA BREEZE FROM SE WILL SHIFT TO BE FROM SW AFTER ABOUT 00Z. ANY TSTMS PASSING NW OF THE AIR FIELD COULD CAUSE A TEMPORARY OUTFLOW FROM THE WEST. FOR SATURDAY...NOW THINKING THAT THE RAIN SHIELD WILL COVER BOS AND PROBABLY CAUSE CIGS AND VSBYS TO LOWER TO MVFR LEVELS. RAIN MAY BE HEAVY FOR A TIME IN THE AFTERNOON. ALTHOUGH RAIN SHOULD TAPER OFF TO SCATTERED SHOWERS SATURDAY EVENING...MVFR CIGS WILL LIKELY PERSIST. KBDL TAF...HIGH CONFIDENCE IN MAINLY VFR CONDITIONS THROUGH TONIGHT. HOWEVER...A TSTM COMPLEX APPROACHING LITCHFIELD COUNTY AT 20Z MAY CAUSE A BRIEF PERIOD OF LOWER CONDITIONS SOMETIME BETWEEN 21Z AND 23Z. FOR SATURDAY...MODERATE CONFIDENCE IN RAIN SHIELD REACHING BDL AND RESULTING IN PERIOD OF MVFR CIGS AND VSBYS. FOR SATURDAY NIGHT...LOW TO MODERATE CONFIDENCE OF MVFR CIGS AND VSBYS IN FOG. OUTLOOK...SUNDAY THROUGH WEDNESDAY... SUNDAY...MVFR CIGS/VSBYS SOUTHEAST WITH IFR ALONG THE SOUTH COAST AND ISLANDS. MAINLY VFR NORTHWEST WITH WIDELY SCATTERED MVFR IN AFTERNOON TSTMS. MONDAY-TUESDAY-WEDNESDAY...MAINLY VFR. SCATTERED AFTERNOON/EVENING SHOWERS/TSTMS WITH BRIEF MVFR CIGS/VSBYS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT... HIGH CONFIDENCE. LIGHT WINDS AND SEAS BELOW SCA ADVISORY EXPECTED THROUGH SATURDAY NIGHT. VISIBILITIES WILL GENERALLY BE GOOD THROUGH TONIGHT...BUT THEN LOWER TO 3 MILES OR LESS IN RAIN AND FOG DURING SATURDAY AND POSSIBLY LOWERING TO A MILE OR LESS IN FOG LATE SATURDAY NIGHT. OUTLOOK...SUNDAY THROUGH WEDNESDAY... SUNDAY...FRONT REMAINS STALLED EITHER OVER OR JUST SOUTH OF THE COASTAL WATERS. AREAS OF POOR VISIBLITY IN RAIN AND FOG AS DISTURBANCES MOVE ALONG THE FRONT. LIGHT WINDS SHIFTING FROM NORTHEAST TO SOUTHEAST. WINDS AND SEAS WILL REMAIN BELOW SMALL CRAFT THRESHOLDS. MONDAY-TUESDAY-WEDNESDAY...LIGHT WINDS MONDAY BECOMING SOUTHWEST TUESDAY. AREAS OF POOR VISIBILITY IN FOG EACH MORNING. SCATTERED THUNDERSTORMS EACH DAY WITH HIGHEST CHANCE ALONG THE NORTH SHORE. WINDS AND SEAS REMAIN BELOW SMALL CRAFT THRESHOLDS. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/THOMPSON NEAR TERM...FRANK SHORT TERM...THOMPSON LONG TERM...WTB AVIATION...WTB/THOMPSON MARINE...WTB/THOMPSON

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