Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 230605 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 205 AM EDT WED JUL 23 2014 .SYNOPSIS...
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HIGH PRESSURE WILL CONTINUE TO MOVE OFFSHORE AS A COLD FRONT APPROACHES FROM THE WEST. THE FRONT WILL MOVE ACROSS FROM WEDNESDAY NIGHT INTO THURSDAY...FOLLOWED BY HIGH PRESSURE ON FRIDAY. THE HIGH WILL WEAKEN ON SATURDAY...THEN LOW PRESSURE PASSING TO THE SOUTHEAST WILL IMPACT THE AREA SUNDAY INTO MONDAY. AN ASSOCIATED COLD FRONT WILL APPROACH LATE DAY MONDAY...AND MOVE ACROSS MONDAY NIGHT INTO TUESDAY.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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SOUTHWEST WINDS BETWEEN A DEPARTING OFFSHORE HIGH PRES SYSTEM AND AN APPROACHING COLD FRONT WILL CONTINUE TO ADVECT WARM MOIST MARITIME TROPICAL AIR ACROSS THE AREA OVERNIGHT. OUR LOCAL AREA WEATHER WILL REMAIN DRY AS STRONG MID AND UPPER LVL SUBSIDENCE ASSOCIATED WITH THE HIGH PRES SYS CONTINUES TO ADVECT SLOWLY EAST ACROSS THE AREA.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/...
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WEDNESDAY...HOT AND INCREASINGLY HUMID AIR MASS REMAINS OVER THE AREA. SFC DEW POINTS WILL RISE THROUGH THE 60S TO AROUND 70. MAX TEMPS WILL TOP OFF IN THE LOWER 90S ACROSS NYC AND NE NJ...AND WILL BE IN THE UPPER 80S TO NEAR 90 ELSEWHERE. TEMPS WILL BE SIGHTLY COOLER NEAR THE SOUTH COASTS. THE HEAT INDEX WILL GENERALLY TOP OFF IN THE LOW TO MID 90S...EXCEPT FOR NYC/NE NJ...WHERE THE HEAT INDEX WILL BE IN THE MID TO UPPER 90S. SINCE THE HEAT INDEX IN NYC WILL NOT REACH 95 FOR 2 CONSECUTIVE DAYS...AND SINCE THE HEAT INDEX WILL REMAIN BELOW 100 ACROSS THE AREA...WILL NOT ISSUE A HEAT ADVISORY. AS COLD FRONT APPROACHES...SHOWERS AND THUNDERSTORMS WILL DEVELOP NORTH AND WEST OF NYC IN THE AFTERNOON ALONG A PRE-FRONTAL TROUGH. SHOWERS AND THUNDERSTORMS SPREAD EAST WEDNESDAY EVENING AND WEDNESDAY NIGHT...AND THE BULK OF THE ACTIVITY SHOULD HOLD OFF UNTIL WEDNESDAY NIGHT AS THE COLD FRONT PASSES THROUGH THE REGION. WITH THE HEAT AND HUMIDITY...ML MUCAPE VALUES WILL RANGE FROM 1000-1500 J/KG DURING THE DAY...AND THEN WILL DROP TO AROUND 400 J/KG AT NIGHT WITH THE LOSS OF THE HEATING. 0-6 KM BULK SHEAR WILL BE WEAK DURING THE DAY...AND THEN WILL RISE TO 25-35 KT AFTER 00Z THURSDAY. CANNOT RULE OUT STRONG WINDS WITH ANY THUNDERSTORMS... BUT PRIMARY THREAT WILL BE HEAVY RAIN DUE TO PRECIPITABLE WATERS AROUND 2 INCHES. FLASH FLOODING OF LOW LYING AND POOR DRAINAGE AREAS IS POSSIBLE. WILL NOT ISSUE A HAZARDOUS WEATHER OUTLOOK AS THE THREAT WILL NOT BE WIDESPREAD. SHOWERS AND THUNDERSTORMS TAPER OFF FROM WEST TO EAST WEDNESDAY NIGHT AS THE COLD FRONT WORKS ITS WAY ACROSS THE REGION. THERE IS A MODERATE RISK OF RIP CURRENTS...MAINLY WEDNESDAY AFT/EVE WITH ENHANCED SEA BREEZE DEVELOPMENT.
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&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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THE SFC COLD FRONT SHOULD BE TO THE EAST THU MORNING...BUT WITH THE H8 FRONT STILL YET TO MOVE ACROSS...A MID LEVEL TROUGH STILL WELL TO THE WEST AND POTENTIAL FOR A WEAK SFC WAVE ALONG THE FRONT TO SLOW ITS PROGRESS EVEN FURTHER...WILL HAVE LIKELY POP TO START ACROSS SE CT AND ERN LONG ISLAND AND CHANCE ELSEWHERE...WITH CHANCES GRADUALLY RAMPING DOWN DURING THE AFTERNOON AND EARLY EVENING. CONDITIONS LOOK MAINLY DRY FOR LATER THU NIGHT AND MORE SO INTO FRI AS HIGH PRESSURE BUILDS FROM THE WEST. THE HIGH SHOULD WEAKEN ON SAT AS FLOW ALOFT BECOMES MORE ZONAL. AS LOW TO MID LEVEL MOISTURE RETURN COMMENCES...WITH PRECIP EFFICIENCY INCREASING BACK TO OVER 1 INCH BY LATE DAY...AND AS MID LEVEL SHORTWAVES APPROACH IN ZONAL FLOW...SHOULD START TO SEE INCREASING CHANCES FOR SHOWERS/TSTMS BEGINNING LATE DAY SAT INTO SAT NIGHT. THE FLOW ALOFT SHOULD UNDERGO SIGNIFICANT AMPLIFICATION EARLY NEXT WEEK AS AN UPPER RIDGE BUILDS IN THE WESTERN STATES AND A POTENT SHORTWAVE TROUGH DIVING OUT OF CENTRAL CANADA MERGES WITH AN UPPER LOW OVER QUEBEC...CARVING OUT A DEEP LONGWAVE TROUGH OVER THE EASTERN STATES. THERE WILL BE GOOD CHANCES FOR SHOWERS/TSTMS... ESPECIALLY SUNDAY NIGHT INTO MON MORNING AS AN ASSOCIATED WAVE OF LOW PRESSURE PASSES JUST OFF TO THE SE...THEN LATE DAY MON INTO MON NIGHT WITH THE APPROACH OF A COLD FRONT FROM THE WEST. COULD SEE SOME LEFTOVER SHOWERS/TSTMS ON TUE MAINLY IN THE MORNING AS THE COLD FRONT MOVES TO THE EAST...THEN DRIER AND SLIGHTLY COOLER AIR ARRIVING THROUGH THE REST OF TUE INTO TUE NIGHT.
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&& .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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A COLD FRONT APPROACHES FROM THE WEST TODAY...THEN BEGINS TO CROSS THE TRI-STATE THIS EVENING. HIGH CONFIDENCE IN VFR INTO THIS AFTERNOON EXCEPT FOR POSSIBLY AT KHPN WITH MVFR FOG POSSIBLE 9-13Z. FOR NOW ADDRESS THUNDER POTENTIAL WITH PROB30 AT ALL TERMINALS EXCEPT KGON - FOR NOW APPEARS THUNDER MOST LIKELY WILL NOT REACH KGON UNTIL AROUND/JUST AFTER 6Z THURSDAY...SO NOT CONFIDENT ENOUGH THERE TO REFLECT IN TAFS. FOR NOW WENT MVFR IN TEMPO GROUPS...HOWEVER WITH LOCALLY HEAVY RAINFALL POSSIBLE IN STRONGER CONVECTION - WOULD NOT BE SURPRISED IF THERE WERE BRIEF PERIODS OF IFR OR LOWER WITH ANY STRONGER STORMS. LIGHT SW FLOW GIVES WAY TO SEABREEZE AT ALL BUT KSWF THIS AFTERNOON. FOR NOW CANNOT RULE OUT OCCASIONAL GUSTS 20-25 KT AT CITY/LONG ISLAND TERMINALS WITH SEABREEZE THIS AFTERNOON. HOWEVER CONFIDENCE IN OCCURRENCE/TIMING IS NOT HIGH ENOUGH TO INCLUDE IN THE TAFS AT THIS TIME. WINDS DIMINISH TO UNDER 10 KT IN THE EVENING...VEERING TO THE NW BEHIND THE FRONT THIS EVENING ACROSS CITY AND NW. .OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY... .LATE WEDNESDAY NIGHT-THURSDAY MORNING...MVFR OR LOWER CONDITIONS IN SCT-NUMEROUS SHRA/TSTMS AND POSSIBLE FOG. .THURSDAY AFTERNOON-SATURDAY MORNING...VFR. .SATURDAY AFTERNOON...MVFR OR LOWER POSSIBLE IN ISOLD SHRA/TSRA MAINLY NW OF NYC. .SATURDAY NIGHT-SUNDAY...CHANCE OF SHRA/TSTMS WITH MVFR OR LOWER POSSIBLE.
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&& .MARINE...
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WINDS WILL GRADUALLY SUBSIDE THROUGH 06Z...WITH SUB-SCA CONDITIONS EXPECTED OVERNIGHT. LOW PROBABILITY OF FOG ON THE WATERS BASED ON FORECAST DEW POINTS NEAR OR SLIGHTLY BELOW WATER TEMPS...SO HAVE REMOVED FROM FORECAST. WINDS WILL INCREASE TO 15-20 KT ONCE AGAIN ON THE OCEAN WATERS WEDNESDAY AFTERNOON AND TO 10-15 KT WITH 15-20 KT GUSTS ON THE REST OF THE WATERS AHEAD OF AN APPROACHING COLD FRONT. CONVECTION LIKELY WEDNESDAY NIGHT. SEAS WILL AVERAGE 2-4 FT ON THE OCEAN AND AROUND 1 FT ELSEWHERE. OUTSIDE OF TSTMS THU AND LATE DAY SAT HAVE HIGH CONFIDENCE IN QUIET CONDITIONS THU THROUGH SAT...THEN FCST UNCERTAINTY CREEPS IN BEGINNING ON SUNDAY. HAVE FCST CONTINUED QUIET CONDITIONS...BUT IF AN APPROACHING WAVE OF LOW PRESSURE AND/OR FRONTAL SYSTEM ARE STRONGER THAN FCST...HAZARDOUS OCEAN SEAS COULD DEVELOP IF CORRESPONDING S-SW FLOW IS STRONGER THAN FCST.
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&& .HYDROLOGY... THERE IS THE POTENTIAL FOR AROUND 1/2 INCH OF RAINFALL FROM LATE WEDNESDAY THROUGH THURSDAY WITH LOCALLY HIGHER AMOUNTS POSSIBLE. PRECIPITABLE WATERS ARE FORECAST TO BE AROUND 2 INCHES ON WEDNESDAY NIGHT...SO LOCALLY HEAVY RAINFALL IS POSSIBLE IN ANY STRONGER CONVECTION. AREAS EXPERIENCING LOCALLY HEAVY RAINFALL COULD EXPERIENCE AT LEAST MINOR FLOODING OF URBAN/POOR DRAINAGE AREA...AND POSSIBLY LOCALIZED FLASH FLOODING. THE CONFIDENCE IN THE LATTER IS CURRENTLY LESS THAN 30 PERCENT SO WILL NOT HIGHLIGHT IN THE HAZARDOUS WEATHER OUTLOOK. LOW PRESSURE PASSING JUST OFF TO THE SE SUNDAY NIGHT INTO MON MORNING...FOLLOWED BY A COLD FRONTAL PASSAGE LATER MON...HAVE SOME POTENTIAL TO PRODUCE HEAVY RAIN...AS PRECIP EFFICIENCY INCREASES TO OVER 1.5 INCHES. THIS WILL DEPEND FIRST ON THE LOW TRACK...THEN ON POTENTIAL FOR TRAINING OF CELLS AHEAD OF THE COLD FRONT...AS WELL AS OTHER MESOSCALE/THERMODYNAMIC FACTORS. GIVEN THESE UNCERTAINTIES IT IS TOO EARLY TO OUTLOOK THIS IN THE HWO. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...GOODMAN/MPS NEAR TERM...GC/MPS SHORT TERM...GC/MPS LONG TERM...GOODMAN AVIATION...MALOIT MARINE...GOODMAN/MPS HYDROLOGY...GOODMAN/MPS

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