AFDBOX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 340 PM EDT FRI JUL 8 2011 .SYNOPSIS... UPPER LEVEL TROUGH MOVES THROUGH THE NORTHEAST USA TONIGHT. THIS WILL GENERATE A WAVE ALONG A STALLED FRONT TO OUR SOUTH. IT WILL ALSO SUPPORT A WEAK COLD FRONT MOVES ACROSS FROM THE GREAT LAKES. ALL OF THIS MOVES EAST OF OUR AREA SATURDAY MORNING. HIGH PRESSURE THEN BUILDS FAIR AND LESS HUMID AIR OVER NEW ENGLAND FOR THE WEEKEND. A COLD FRONT SHOULD GRADUALLY SLIDE THROUGH THE REGION THROUGH TUESDAY...BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS. HIGH PRESSURE RETURNS WEDNESDAY INTO THE END OF THE WEEK. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... NAM AND GFS SHOW RIGHT ENTRANCE REGION OF UPPER JET OVER SOUTHERN NEW ENGLAND THIS EVENING. ACTUALLY THE GFS SHOWS A SECOND JET STREAK OVER SOUTHERN NEW ENGLAND. THE SURFACE INFLOW IN RESPONSE TO THIS FEATURE APPEARS TO BE GENERATING A ZONE OF FRONTOGENETIC FORCING ACROSS LONG ISLAND AND ALONG OUR SOUTHERN COAST. ALL OF THIS IS IN SUPPORT OF A WAVE ALONG THE STALLED FRONT TO OUR SOUTH AS WELL AS A WEAK COLD FRONT MOVING ACROSS FROM THE GREAT LAKES. UPPER SHORTWAVE MOVES ACROSS SOUTHERN NEW ENGLAND AROUND 06Z/2AM...SO THESE FEATURES SHOULD MOVE OFF TO OUR EAST BY SATURDAY MORNING. MID LEVEL LAPSE RATES REMAIN UNIMPRESSIVE...BUT THERE WILL BE SOME CAPE AND THE LIFTED INDEX REMAINS BELOW ZERO THROUGH THE NIGHT. SO CONVECTION IS EXPECTED. PRECIP WATER VALUES ARE AROUND 1.75 INCHES...SUPPORTING HEAVY DOWNPOURS. AFTER THE DOWNPOURS THAT SOUTHERN AREAS RECEIVED THIS MORNING...THERE IS POTENTIAL FOR LOCALIZED FLOODING IF ANY LATE AFTN AND EVENING CONVECTION MOVES OVER THESE AREAS. SEVERE TSTM WATCH IN EFFECT FOR CONNECTICUT THROUGH 9 PM. MOST OF THE SUPPORT FOR SEVERE SEEMS TO BE MORE LIKE NYC AND POINTS SOUTH...POSSIBLY SOUTHWEST CONNECTICUT. WE USED A BLEND OF MOS FOR OVERNIGHT TEMPS/DEWPOINTS. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... SATURDAY AND SATURDAY NIGHT... HIGH PRESSURE BUILDS OVER THE REGION. EXPECT DRY WEATHER. 800 MB TEMPS ARE FORECAST AROUND 10-11C...FULLY MIXED THIS WOULD MEAN MAX TEMPS IN THE MID 80S. WE USED A BLEND THAT SHOWS MAX TEMPS IN THE LOW TO MID 80S. DEWPOINTS EXPECT TO FALL INTO THE 50S DURING THE DAY...SO NIGHTTIME MIN TEMPS SHOUD REACH THE 50S EXCEPT LOWER 60S IN SOME OF THE LARGER CITIES. && .LONG TERM /SUNDAY THROUGH FRIDAY/... MAIN POINTS... *COOLER AND DRIER WEATHER ASSOC WITH HIGH PRES FOR SUNDAY *COLD FRONT WITH SHOWERS AND THUNDERSTORMS MONDAY INTO TUESDAY *UNSEASONABLY COOL WEATHER BEGINNING WEDNESDAY INTO THE END OF THE WEEK *ANOTHER WET WEATHER SYSTEM POSSIBLE INTO THE WEEKEND OVERVIEW... 0Z NAM HAS FINALLY COME INTO CONSENSUS WITH MDL SOLNS...MORESO WITH THE OUTCOMES FCST BY THE GFS FOR THE LAST SEVERAL DAYS CONCERNING SHRTWV ENERGY THRU THE SRN BRANCH OF THE MID-LVL TROF INTO THE END OF THIS WEEK USHERING CYCLOGENESIS OFF THE SHORELINE OF THE DELMARVA PENINSULA AND ELONGATING ALONG THE STALLED QUASI-STATIONARY FRONTAL BOUNDARY S OF NEW ENGLAND. AS SUCH FOR THE EXTENDED PD PLACED GREATER WEIGHT UPON THE 0Z GFS...WHILE TAKING INTO CONSIDERATION THE CONSISTENT NATURE OF THE ECMWF. WEIGHTED MORESO WITH BIAS-CORRECTED MAV GUIDANCE TRANSITIONING TO THE BIAS-CORRECTED MOS GUIDANCE. DETAILS... SATURDAY NIGHT THRU SUNDAY NIGHT... SFC HIGH PRES SETTLES ACROSS THE RGN SATURDAY NIGHT INTO SUNDAY MORNING...GRADUALLY PROGRESSING E INTO SUNDAY NIGHT...ALLOWING FOR A PERIOD OF SEASONABLY/DRY WX. LGT/VRB SFC FLOW COUPLED WITH NVA- SUBSIDENCE AND MUCH DRIER /SLIGHTLY COOLER/ AIR WILL MAKE FOR A GOOD CASE OF NOCTURNAL COOLING AT THE SFC FOR SUNDAY MORNING LOWS. EXPECTING LOW SFC DEWPOINTS ATTENDANT WITH THE SFC HIGH PRES WILL ALLOW FOR MINS TO FALL INTO THE MID-UPR 50S ACROSS THE N/W NH AND MA...INTO THE LOW 60S FURTHER S AND CLOSER TO SHORE. SUNDAY WILL SEE RETURN ONSHORE SFC SLY FLOW AS THE SFC HIGH SHUNTS E...WITH SW FLOW AT MID-LVLS ADVECTING WARM AND MOIST AIR OVER THE RGN. SFC S FLOW MAY BE LIGHT ENOUGH TO ALLOW SEA-BREEZES ALONG THE E SHORELINE. OTHERWISE EXPECT WITH THE MOISTURE RETURN FOR SOME CU DVLPMNT TOWARDS THE AFTN...YET ANTICYCLONIC FLOW WILL STILL BE PREVALENT EXPECT SCT /RATHER THAN BKN/ CU MIXING UP TO H85/5-7 KFT... ESPECIALLY ALONG W SLOPES OF TERRAIN WHERE MID-LVL MOIST AND Q-VECT CONV MAY BE BETTER DEFINED. RETURN OF H925 TEMPS TO +18-20C SHOULD ALLOW SFC TEMPS TO REBOUND INTO THE UPR 70S/LOW 80S. SUNDAY NIGHT WILL CONTINUE TO SEE CONTINUED WARMING/MOISTENING AT MID-LVLS AIDED BY W/SW FLOW ALOFT. SHOULD BE A SLIGHTLY WARMER NIGHT IN TERMS OF MINS AS MID-UPR LVL CLOUDS WILL LIKELY BE STREAMING ACROSS THE RGN ALONG THE MEAN LYR FLOW AHEAD OF THE NEXT SYS FOR THE BEGINNING OF THE WEEK. MONDAY THRU TUESDAY NIGHT... MATURATION PHASE OF LOW PRES ACROSS ERN CANADA WILL AMPLIFY THE E-W THERMAL AXIS/H3 JET STREAK IN PROXIMITY OF THE N GRT LKS RGN INTO N NEW ENGLAND THEREBY AMPLIFYING ATTENDANT SHRTWV DISTURBANCES ALONG THE MEAN LYR FLOW. ALTHO MDL DISCREPANCIES EXIST AMONGST THE GFS/ ECMWF IN HANDLING THE AFOREMENTIONED FEATURES...THERE IS AGREEMENT UPON A GENERAL TREND IN WHERE SHRTWV DISTURBANCES SHOULD AT LEAST PROVIDE ENHANCED ASCENT OF AVAILABLE MOISTURE/INSTABILITY THAT HAS BEEN PUMPED ACROSS THE RGN ALONG THE WRN PERIPHERY OF THE DEPARTING SFC HIGH PRES...WITH BETTER DYNAMICS CONFINED TO N NEW ENGLAND MONDAY NIGHT INTO TUESDAY. HAVE GREATER CONFIDENCE IN 0Z GFS OUTCOME...AMPLIFICATION OF SHRTWV ENERGY THRU N NEW ENGLAND SHOULD DRAG COOLER AIR SEWD ALONG AND BEHIND A COLD FRONT...ESPECIALLY AT MID-LVLS...WHICH SHOULD PROVIDE ENOUGH FRONTOGENETICAL FORCING OF WARM/MOIST UNSTABLE AIR ALONG AND AHEAD. TIMING OF THIS FRONTAL BOUNDARY REMAINS STILL IN QUESTION...AND WHETHER INSTABILITY ALONG AND AHEAD WILL BE SFC BASED. SHOULD CONVECTION FIRE IN THE VICINITY OF THE E GRT LKS AND PROGRESS E WITH THE COLD FRONT MON AFTN CONTINUING INTO TUE...NOT CERTAIN IF SFC DESTABILIZATION WILL OCCUR WITH POTENTIAL CLOUD COVER OVERSPREADING THE RGN FROM THE W. DETAILS ARE STILL SKETCHY AT THIS TIME...NEVERTHELESS FEEL BEST POP CHS FOR SHOWERS/THUNDERSTORMS WILL BE ON TUESDAY INTO TUESDAY NIGHT AS WARM/MOIST UNSTABLE AIR...AIDED BY STRONG AND POTENTIALLY GUSTY SW FLOW...WILL BE READILY AVAILABLE ALONG AND AHEAD OF THE EXPECTED COLD FRONT. WEDNESDAY INTO THE END OF THE WEEK... MDL SOLNS CONTINUE TO HIGHLIGHT A STRONG SFC HIGH PRES RIDGE IN CONTROL OF THE RGNS WX BRINGING COOLER AND MUCH DRIER CONDITIONS TO THE RGN. INITIALLY MODEST N/NW FLOW...WITH GUSTS 20-25 KTS...BEHIND THE EXITING SYS WILL USHER SOME VERY COOL MID-LVL AIR SEWD WITH H925 TEMPS AS +10C. WILL SEE MIN TEMPS FALL INTO THE LOW TO MID 50S... WARMER ALONG THE SHORE. SOME AREAS REPORTING UPR 40S FOR MINS WED/THURS MORN IS NOT OUT OF THE QUESTION. MAX TEMPS FOR THESE TWO DAYS WILL RANGE IN THE LOW TO MID 70S...COOLER ALONG THE SHORE. VERY UNSEASONABLE WX! WILL SEE LGT/VRB NLY FLOW ON THURS GRADUALLY VEER OUT OF THE S/SW BY FRIDAY...SO THEREAFTER EXPECT A GRADUAL WARMING TREND ALONG AND AHEAD OF ANOTHER WET WX SYS FOR THE WEEKEND. ANTICIPATE MOSTLY CLEAR CONDITIONS FOR MUCH OF THE TIMEFRAME... PERHAPS DIURNAL CU DURING THE DAY WEDNESDAY...WITH INCREASING CLOUDS RETURNING INTO LATE FRI INTO SAT. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT MODERATE...30 PERCENT TO 60 PERCENT HIGH...GREATER THAN 60 PERCENT THIS EVENING AND TONIGHT... GENERALLY MVFR CEILINGS WITH PATCHY IFR IN SHOWERS. LIFR CEILINGS AND VSBYS IN FOG AND SHOWERS/TSTMS. HIGH CONFIDENCE. SATURDAY AND SATURDAY NIGHT... HIGH PRESSURE BUILDS OVER THE REGION. EXPECT VFR CONDITIONS. POSSIBLE LINGERING LIFR IN FOG ON CAPE COD AND ISLANDS SATURDAY MORNING...BUT THIS SHOULD LIFT DURING THE MORNING. HIGH CONFIDENCE. KBOS TERMINAL...MVFR CEILINGS WITH OCCASIONAL IFR/LIFR IN SHOWERS/TSTMS MOSTLY FROM 22Z TO 07Z. CONDITIONS IMPROVING TO VFR WITH A WIND SHIFT...WINDS OUT OF THE NORTHWEST AFTER 12Z. OUTLOOK...SUNDAY THROUGH TUESDAY... SUNDAY... MEDIUM CONFIDENCE VFR. LGT AND VRB INTO SUNDAY MORNING AND SLOWLY VEERING OUT OF THE S/SW INTO SUNDAY NIGHT. COULD STILL SEE SOME RESIDUAL FOG THRU THE OVRNGT HRS FOR THE WEEKEND ALONG THE SE TERMINALS OUT ALONG THE CAPE/ISLANDS. LOW CONFIDENCE AT THIS TIME. MONDAY INTO TUESDAY NIGHT... MEDIUM CONFIDENCE VFR/MVFR. ANOTHER COLD FRONT APPROACHING THE TERMINALS ALONG AND AHEAD OF WHICH SHRA/TSRA WILL DEVELOP. FEEL LOW VSBY/CIG IMPACTS WILL BE PRIMARILY SUITED FOR THE N/W TERMINALS MONDAY...TRANSITIONING SEWD TOWARDS SE NEW ENGLAND INTO TUESDAY. S/SW FLOW GUSTING AT TIMES 15 TO 20 KTS PSBL. ANY TSRA IMPACTING THE TERMINALS WILL LIKELY RESULT IN TEMPO IFR/LIFR VSBYS AND CIGS. SIGNIFICANT WEATHER SHOULD BE THRU THE TERMINALS BY TUESDAY NIGHT. && .MARINE... TONIGHT... WINDS AND SEAS REMAIN BELOW SMALL CRAFT LEVELS. POOR VSBYS FROM DENSE FOG ESPECIALLY AROUND CAPE COD AND THE ISLANDS. TSTMS MAY PRODUCE HEAVY RAIN AND GUSTY WINDS. SATURDAY AND SATURDAY NIGHT... SEAS MAY BUILD TO 5-6 FEET ON THE SOUTHERN WATERS...MOSTLY A SOUTH-SOUTHWEST SWELL. A SMALL CRAFT ADVISORY HAS BEEN ISSUED. OUTLOOK...SATURDAY NIGHT THROUGH TUESDAY NIGHT... SUNDAY... SEAS OF AROUND 5 TO 6 FEET WILL CONTINUE ACROSS THE S OPEN WATERS AS A RESULT OF SWELL GENERATED BY SLY WINDS S OF A STATIONARY FRONTAL BOUNDARY DRAPED S OF NEW ENGLAND. ANTICIPATE SEAS BELOW SCA THRESHOLDS BY SUNDAY. MONDAY INTO TUESDAY NIGHT... A COLD FRONT APPROACHES THE REGION ALONG AND AHEAD OF WHICH S/SW WINDS WILL INCREASE...WITH GUSTS UP TO 25 KTS POSSIBLE PRIMARILY FOR TUESDAY. WILL SEE SEAS BUILD IN CONCERT WITH STRONG AND GUSTY SW WINDS UP TO 5 TO 6 FEET FOR THE OPEN WATERS AND PERHAPS FOR SOME OF THE WATERS ALONG THE S AND CLOSE TO SHORE. && .HYDROLOGY... MORNING RAINFALL IN TSTMS WAS HIGHEST OVER COASTAL SOUTHEAST MASS WITH BETWEEN 1 AND 1.5 INCHES FROM TIVERTON RI THROUGH NEW BEDFORD TO CHATHAM. ALSO OTHER BANDS OF 1 INCH OR MORE ACROSS CENTRAL RI...SOUTHCENTRAL MASS...NW HAMPDEN AND SOUTHERN HAMPSHIRE COUNTIES IN MASS. FLASH FLOOD GUIDENCE IS GENERALLY AT 2-3 INCHES PER HOUR AND 3.5 TO 4.5 IN 3 HOURS. COULD BE LOCAL URBAN/SMALL STREAM/POOR DRAINAGE FLOODING IN THESE AREAS IF ADDITIONAL HEAVY DOWNPOURS MOVE ACROSS THIS EVENING AND TONIGHT. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...NONE. MA...NONE. NH...NONE. RI...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 7 AM SATURDAY TO 5 AM EDT SUNDAY FOR ANZ235-254>256. && $$ SYNOPSIS...WTB/SIPPRELL