556 FXUS61 KBOX 120301 AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 1101 PM EDT THU JUL 11 2013 .SYNOPSIS... A COLD FRONT MOVES OFFSHORE TONIGHT AND THEN STALLS SOUTH OF NEW ENGLAND. LOW PRESSURE MOVES ALONG THE FRONT UP THE COAST FRIDAY AND SATURDAY BRINGING ADDITIONAL SHOWERS TO THE REGION. HEAT AND HUMIDITY WILL INCREASE EARLY NEXT WEEK. AFTERNOON SHOWERS AND THUNDERSTORMS WILL BE ALSO BE POSSIBLE. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 1050 PM UPDATE... COLD FRONT CONTINUES TO SLOWLY MOVE S ACROSS SE MA/RI/N CT AT 02Z. NOTED A FEW SHOWERS THAT HAVE DEVELOPED ALONG THIS BOUNDARY... NAMELY CLOSE TO BOSTON BUT WERE MAINLY BRIEF DOWNPOURS AS LAST OF HIGH DEWPT AIRMASS SHIFTS S. OTHERWISE...REMAINDER OF ORGANIZED PRECIP HAS PUSHED OFFSHORE PER LATEST RADAR TRENDS. NOTED REPORT FROM MARTHAS VINEYARD FERRY OF DENSE FOG DURING THE CROSSING WITH VSBYS BELOW 1/2 MILE...BUT 1-2 MILES ON THE ISLAND ITSELF. EXPECT POCKETS OF LOW VSBYS OVER THE SOUTHERN NEAR SHORE WATERS THAT SHOULD IMPROVE AS DRIER AIR TRIES TO WORK IN OVERNIGHT. WILL MONITOR. HAVE UPDATED GRIDS TO BRING CONDITIONS CURRENT. PREVIOUS DISCUSSION... THE FRONT WILL CONTINUE TO DRIFT SOUTHEAST EARLY TONIGHT WITH ANY LINGERING SHOWERS TAPERING OFF. EXPECT A RAIN-FREE NIGHT WITH DEWPOINTS EITHER IN OR MOVING TO THE LOW-MID 60S. LIGHT WINDS WILL ALLOW AREAS OF FOG TO DEVELOP WITH THE LOWEST VISIBILITY ALONG THE SOUTH COAST. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... FRIDAY...THERE IS QUITE A BIT OF UNCERTAINTY IN THE FRIDAY FORECAST WITH THE NAM/GFS INDICATING A WAVE OF LOW PRESSURE MOVING ALONG THE FRONT AND BRINGING RAIN INTO AT LEAST THE SOUTHERN PARTS OF THE REGION. THE ECMWF HAS A STRONGER HIGH PRESSURE BUILDING SOUTH INTO SOUTHERN NEW ENGLAND WHICH PUSHES THE FRONT FARTHER SOUTH AND DOES NOT HAVE THAT SAME WAVE OF LOW PRESSURE. IF THE ECMWF IS RIGHT...DONT SEE RAIN REACHING ANY FARTHER NORTH THAN THE SOUTH COAST...IF THAT. IF THE NAM/GFS IS RIGHT...THERE IS MUCH MORE UNCERTAINTY IN HOW FAR NORTH THE RAIN WILL REACH WITH THE HIGHEST LIKELIHOOD FOR RAIN SOUTH OF THE MASS PIKE. ONE THING WE ARE MORE CONFIDENT IN IS COOLER TEMPERATURES AND DEWPOINTS BELOW 70 DEGREES WHICH MAKES FOR A MUCH LESS HUMID DAY...PARTICULARLY ACROSS THE NORTHERN ZONES. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... BIG PICTURE/PREFERENCES... UPPER LOW OVER THE APPALACHIANS SHIFTS WEST TO THE MISSISSIPPI OVER THE WEEKEND AND TO THE PLAINS EARLY NEXT WEEK. WEST ATLANTIC HIGH PRESSURE BUILDS OVER THE EASTERN USA. THE UPPER JET SHIFTS TO A ZONE FROM THE PACIFIC NORTHWEST THROUGH CANADA. SURFACE HIGH REMAINS PARKED OVER THE WEST ATLANTIC THROUGH THE FORECAST PERIOD WITH A MOIST SOUTHWEST LOW LEVEL FLOW INTO SOUTHERN NEW ENGLAND. THIS ALLOWS MOISTURE AND INSTABILITY REMAIN HIGH DURING THE PERIOD. TEMPERATURE FIELDS REMAIN SIMILAR OVER THE WEEKEND AND EARLY WEEK...THEN SHOW A WARMING TREND TUESDAY TO THURSDAY. PREFER A BLEND OF LONG RANGE DATA. THE DAILIES... FRIDAY NIGHT-SATURDAY... SURFACE FRONT STALLS SOUTH OF NEW ENGLAND. LOW PRESSURE WAVE GENERATED ALONG THE FRONT BY APPALACHIAN UPPER LOW AND ASSOCIATED JET. THIS MOVES UP THE FRONT FRIDAY NIGHT FURTHER SUPPORTED BY THE RIGHT ENTRANCE REGION OF DEPARTING JET TO OUR NORTH. THE LOW ALSO AIMS A 30-KNOT LOW LEVEL JET THAT RIDES OVER THE FRONT AND ACROSS RI/EASTERN MASS. ALL OF THIS MEANS PLENTY OF LIFT AND VENTING...AND AN AIRMASS THAT CONTINUES TO HAVE 1.5 TO 2.2 INCH PRECIPITABLE WATER VALUES. WILL GO WITH LIKELY POPS FRIDAY NIGHT TRENDING TO CHANCE POPS ON SATURDAY...WITH LOCALLY HEAVY DOWNPOURS MENTIONED. MIXING TO 850 MB WOULD SUPPORT MID 80S...MIXING TO 900 MB WOULD SUPPORT TEMPS AROUND 80 OR LOW 80S. CLOUDS AND A NORTHEAST FLOW NORTH OF THE STALLED FRONT SHOULD KEEP TEMPS TOWARD THE COOLER TARGETS. SUNDAY THROUGH THURSDAY... WITH HIGH PRESSURE ALOFT THE LARGE SCALE SUPPORT FOR SHOWERS/TSTMS IS LIMITED. BUT MOISTURE AND INSTABILITY REMAIN HIGH...SOLAR HEATING OR CONVERGENCE ALONG A BOUNDARY /SUCH AS A SEABREEZE/ COULD SET OFF CONVECTION EACH DAY. LATE IN THE PERIOD AS THE UPPER HIGH SHIFTS FARTHER WEST AND OUR FLOW TURNS NORTHWEST THERE WILL BE MORE ROOM FOR ANOTHER COLD FRONT TO MOVE SOUTH OUT OF CANADA. EXPECT CHANCE POPS FOR SHOWERS/TSTMS EACH DAY. TEMPS AT 850 MB ARE FORECAST AT 16-19C...COOLEST ON SUNDAY. THIS WOULD SUPPORT MAX SURFACE TEMPS 85-95F DURING THE PERIOD. NIGHTTIME WINDS WILL BE LIGHT AND DEWPOINTS IN THE UPPER 60S AND 70S...SO EXPECT OVERNIGHT MIN TEMPS UPPER 60S AND 70S. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. MODERATE CONFIDENCE...BUT LOW CONFIDENCE IN TIMING ANY SHOWERS AND THUNDERSTORMS INTO TERMINALS. TONIGHT...VFR IN GENERAL...BUT WITH AREAS OF FOG DEVELOPING ESPECIALLY ALONG THE SOUTH COAST. IFR/LIFR CIGS/VSBYS ARE MOST LIKELY ACROSS THE SOUTH COAST AND THE ISLANDS. FOG FARTHER NORTH MAY BRING MVFR VSBYS. FRIDAY...EXPECT MOSTLY VFR CONDITIONS WITH THE EXCEPTION OF ALONG THE SOUTH COAST...CAPE...AND ISLANDS WHERE MVFR/IFR CONDITIONS ARE LIKELY. CONDITIONS MAY LOWER AS RAIN MOVES NORTHWARD OVER THE AREA BUT IT IS UNCERTAIN HOW FAR NORTH THE RAIN WILL SPREAD. KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. OUTLOOK...FRIDAY NIGHT THROUGH TUESDAY... MODERATE CONFIDENCE. NO CHANGES IN THE WEATHER PATTERN THROUGH MUCH OF THE UPCOMING WEEK. THIS WILL MEAN SHOWERS AND SCATTERED TSTMS THROUGH AT LEAST WEDNESDAY...SOME WITH HEAVY DOWNPOURS. THE DAYTIME MAY HAVE BASELINE OF VFR...BUT WITH MVFR/IFR CIGS AND VSBYS IN ANY SHOWERS/TSTMS. THE VERY HUMID AIRMASS LINGERS THROUGH THE PERIOD...SO NIGHT AND MORNING FOG WILL BRING IFR/LIFR CIGS/VSBYS. THE LOW CLOUDS AND FOG MAY LINGER DURING THE DAY ACROSS PARTS OF THE CAPE AND ISLANDS. && .MARINE... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT. MODERATE...30 TO 60 PERCENT. HIGH...GREATER THAN 60 PERCENT. SMALL CRAFT ADVISORY HAS BEEN EXTENDED INTO THE OVERNIGHT HOURS ON THE SOUTHERN OUTER WATERS. SEAS OF 5 FEET CONTINUE TO BE REPORTED SOUTHEAST OF BLOCK ISLAND. SEAS WILL DIMINISH GRADUALLY AFTER THE FRONT MOVES THROUGH THE WATERS. SHOWERS AND THUNDERSTORMS MAY LIMIT VISIBILITIES AT TIMES THROUGH THIS EVENING AND AGAIN ON FRIDAY. OUTLOOK...FRIDAY NIGHT THROUGH TUESDAY... MODERATE CONFIDENCE NO CHANGE IN THE WEATHER PATTERN THROUGH MUCH OF THE UPCOMING WEEK. THIS WILL MEAN SHOWERS/TSTMS/FOG WITH VERY HUMID AIR. THERE WILL BE POOR VSBYS AT TIMES...AND 1/4 MILE VSBYS IN FOG POSSIBLE EACH NIGHT AND MORNING. SOUTH TO SOUTHWEST WINDS THROUGH THE PERIOD. WIND GUSTS WILL BE 20 KNOTS OR LESS. BUT THE STEADY WIND DIRECTION WILL HELP BUILD SEAS WITH WAVE HEIGHTS OF 5 TO 10 FEET EXPECTED ACROSS THE OUTER COASTAL WATERS AND EXPOSED PORTIONS OF THE SOUTHERN SOUNDS SUCH AS RI SOUND AND POSSIBLY BLOCK ISLAND SOUND. A SMALL CRAFT ADVISORY WILL BE NEEDED FOR THESE ROUGH SEAS THROUGH MIDWEEK...ESPECIALLY ACROSS THE OUTER COASTAL WATERS. && .HYDROLOGY... STILL NOTING A FEW BRIEF HEAVY SHOWERS BUT ISOLATED IN NATURE. REMAINDER OF ORGANIZED PRECIP HAS MOVED OFFSHORE. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...NONE. && $$ SYNOPSIS...WTB/RLG NEAR TERM...WTB/EVT SHORT TERM...RLG LONG TERM...WTB AVIATION...WTB/RLG MARINE...WTB/RLG/EVT HYDROLOGY...EVT