AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 357 AM EDT FRI JUL 8 2011 .SYNOPSIS... A FRONTAL BOUNDARY WILL REMAIN OVER THE AREA TODAY AS WEAK DISTURBANCES RIDE ALONG IT. THE FRONT WILL DRIFT SOUTH OF THE AREA FRIDAY NIGHT...AND REMAIN JUST SOUTH OF THE AREA THROUGH SATURDAY. HIGH PRESSURE WILL THEN BUILD IN FROM THE GREAT LAKES FOR THE WEEKEND...AND THEN SLIDE EAST ON MONDAY. A COLD FRONT WILL MOVE ACROSS ON TUESDAY...FOLLOWED BY CANADIAN HIGH PRESSURE FOR THE REST OF THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... SCT SHOWERS MOVING INTO NYC METRO ATTM...TO BE FOLLOWED BY ANOTHER LARGE BUT WEAKENING CLUSTER OF SHOWERS/TSTMS OVER SW PA AFTER DAYBREAK. SHOWERS/TSTMS SHOULD INCREASE FURTHER IN AREAL COVERAGE BY LATE MORNING OR AFTERNOON WITH PW NEAR 2 INCHES...LIFT VIA PRESENCE OF E-W ORIENTED STATIONARY FRONT OVER THE AREA PLUS EVENTUAL SEA BREEZE BOUNDARIES...AND ARRIVAL OF A MID LEVEL VORT MAX AND UPPER DIVERGENCE IN THE RIGHT REAR QUAD OF A JET STREAK PASSING TO THE NORTH...AND BUILDING INSTABILITY WITH DAYTIME HEATING. WITH LACK OF A DECENT SOUTHERLY LLJ OVERRIDING THE FRONT DO NOT THINK HEAVY RAIN THREAT WILL BE WIDESPREAD ENOUGH TO WARRANT A FLASH FLOOD WATCH...HOWEVER ANY STRONGER STORMS TODAY COULD DUMP A QUICK 1-2 INCHES OF RAIN. MID LEVEL FLOW OF 25-30 KT AND SBCAPE 1000-1500 J/KG SUGGEST POTENTIAL FOR ISOLATED SVR STORMS AS WELL. NOT QUITE AS WARM TODAY WITH ABUNDANT CLOUD COVER/PRECIP AND ONSHORE FLOW. HIGHS SHOULD RANGE FROM THE MID 80S IN URBAN NORTHEAST NJ...TO WITHIN A COUPLE DEGREES OF 80 ELSEWHERE. THERE IS A MODERATE RIP CURRENT RISK AT THE OCEAN BEACHES TODAY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... THE FRONT WILL DROP S THROUGH THE AREA TONIGHT AS A WEAK LOW RIDES ALONG IT AND QUICKLY MOVES INTO THE OFFSHORE WATERS S OF LONG ISLAND BY SATURDAY MORNING. CHANCE/LIKELY POP THIS EVENING WILL GRADUALLY TAPER OFF OVERNIGHT. LOWS IN THE 60S TO LOWER 70S EXPECTED. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... CANADIAN HIGH PRESSURE BUILDS OVER THE REGION ON SUNDAY WITH SW WARM ADVECTION AND HUMIDITY RETURNING ON MONDAY. DEWPOINTS OF AROUND 60 ON SUNDAY RISE TO UPPER 60S ON MONDAY AS MARITIME TROPICAL AIR RETURNS ONCE AGAIN. KEPT IT DRY ON MONDAY...AS INSTABILITY IS LIMITED AND SUBSIDENCE ALOFT SHOULD SUPPRESS ANY DIURNALLY DRIVEN CONVECTION. MAIN WEATHER EVENT FOR THE LONG TERM PERIOD IS A COLD FRONT THAT ORIGINATES WITH SHORTWAVE CURRENTLY OVER BRITISH COLUMBIA. EXAMINATION OF THE 12Z AND 18Z GEFS WITH AGREEMENT FROM THE 12Z ECMWF AND LATEST GEM ALL SUPPORT COLD FRONTAL PASSAGE TUESDAY. HAVE FOCUSED PCPN CHANCES FOR THE DIURNALLY FAVORED AFTN PERIOD. EARLY ESTIMATES OF CAPE FOR TUESDAY AFTN ARE MODERATE AT AROUND 2000 J/KG WITH WEAK TO MODERATE SHEAR OF 30-35 KT IN THE 0-6 KM LAYER. SO HAVE SOME POTENTIAL FOR SEVERE DEPENDING ON THE TIMING OF THE FRONT. NOTE...THIS DIFFERS FROM PREVIOUS FCSTS...THOUGH WITH SUPPORT FROM THE GLOBAL ENSEMBLES AND DETERMINISTIC RUNS...CONFIDENCE IS HIGH ENOUGH TO DEVIATE FROM CONTINUITY ATTM. HIGH PRESSURE AND LOW HUMIDITY RETURN FOR WEDNESDAY THROUGH THE END OF THE WEEK. TEMPS ARE FCST BASED ON LATEST MOS AND WARM TO SLIGHTLY ABOVE NORMAL ON MONDAY. MONDAY AND TUESDAY SHOULD SEE LOWER 90S FOR NE JERSEY...AND APPROACHING 90 IN NYC. THE HIGH DEW POINT TEMPERATURES RESULTS IN HEAT INDEX VALUES IN THE LOWER AND MID 90S FOR THESE AREAS. COMFORTABLE MID SUMMER WEATHER RETURNS ON WEDNESDAY WITH LOWER 80S FOR MAXES AND DEW POINT TEMPS IN THE MID 50S. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... A TROUGH OF LOW PRESSURE WILL DRIFT TO OUR SOUTH THIS MORNING...THEN STALL OUT S OF LONG ISLAND. WAVES OF LOW PRESSURE WILL THEN MOVE NE ALONG IT THROUGH TONIGHT. PRIMARILY VFR TO START...THOUGH CT AND LONG ISLAND TERMINALS HAVE SHOWN SOME PATCHY IFR STRATUS...THIS COULD CONTINUE THROUGH THE EARLY MORNING HOURS. IT APPEARS MOST TERMINALS SHOULD SEE SOME MVFR FOG TOWARDS THE MORNING PUSH...WITH CT/LONG ISLAND TERMINALS AND KHPN LIKELY SEEING VFR FOG. OCCASIONAL SHOWERS WITH EMBEDDED THUNDERSTORMS LIKELY FROM MID MORNING INTO THIS EVENING. SHOULD PRIMARILY BE VFR...EXCEPT CT/LONG ISLAND TERMINALS/KHPN WHICH SEEM MORE PRONE TO MVFR WITH FOG IN ADDITION TO THE CONVECTION. CANNOT RULE OUT ISOLD MVFR-IFR IN STRONGER CONVECTION...BUT NOT CONFIDENT ENOUGH AT THIS TIME TO PIN POINT WHEN/WHERE THIS WILL OCCUR...SO DO NOT HAVE IN TAFS...SAME WITH TIMING OF THUNDER...HENCE ONLY CBS IN TAFS AT THIS TIME. WITH WEAK FRONTAL BOUNDARY MOVING TO S...AND WEAK WAVES OF LOW PRESSURE MOVING ALONG IT...WIND DIRECTION WILL BE HIGHLY VARIABLE TODAY FROM NE TO SW...BUT SPEEDS SHOULD GENERALLY BE AT OR BELOW 6 KT. EXCEPTION IS CITY TERMINALS/KISP/KBDR THIS AFTERNOON WHICH COULD SEE SPEEDS JUST ABOVE 6 KT...USED A SE DIRECTION AT THOSE TERMINALS...BUT COULD BE ANYTHING FROM E TO S. WINDS BECOME LIGHT AND VARIABLE THIS EVENING AT ALL TERMINALS. OUTLOOK FOR 06Z FRIDAY THROUGH TUESDAY... LATE FRIDAY NIGHT...SUB-VFR POSSIBLE IN LINGER SHRA/TSRA AND POST- RAIN INDUCED FOG. SATURDAY MORNING...BECOMING VFR. SATURDAY AFTERNOON-MONDAY...VFR. MONDAY NIGHT-TUESDAY...CHANCE OF MVFR OR LOWER LATE MONDAY NIGHT/TUESDAY MORNING WITH LOW STRATUS/FOG...THEN SUB-VFR POSSIBLE WITH SHRA/TSRA LATER IN THE DAY AHEAD OF A COLD FRONT. && .MARINE... GENERALLY QUIET WITH RESPECT TO WINDS/WAVES...BUT CONVECTION COULD PRODUCE LOCALLY GUSTY WINDS AND REDUCED VSBY TODAY INTO THIS EVENING. S SWELL GENERATED BY HIGH PRESSURE OFF THE S COAST WILL SPREAD NORTHWARD TODAY INTO SAT...AND WAVEWATCH INDICATES 5 FT OCEAN SEAS POSSIBLE SAT AFTERNOON. ATTM EXPECT CURRENT 7 FT SEAS OFF THE NC COAST TO DECAY TO JUST UNDER 5 FT BEFORE THEY REACH OUR COASTAL WATERS. INCREASING S FLOW AHEAD OF A COLD FRONT MAY AGAIN BUILD OCEAN SEAS TO NEAR 5 FT ON TUE. && .HYDROLOGY... HEAVY RAINFALL OF 1-2 INCHES IS POSSIBLE TODAY INTO THIS EVENING WITH ANY STRONGER CONVECTION...WHICH WOULD CAUSE LOCALIZED URBAN/POOR DRAINAGE FLOODING. SMALL STREAM FLOODING MAY ALSO BE POSSIBLE IN NORTHEAST NJ IF RAINFALL OF THIS MAGNITUDE FALLS IN AN HOUR OR LESS. THE OVERALL THREAT DOES NOT LOOK TO BE WIDESPREAD ENOUGH TO WARRANT A FLASH FLOOD WATCH. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$