Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 221945 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 345 PM EDT TUE JUL 22 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 BUILDING 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 WEDNESDAY MORNING/...
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SOME WEAK UPPER LEVEL ENERGY WILL SPILL OVER THE TOP OF THE RIDGE ALONG THE NORTHEAST THIS EVENING. SOME WIDELY ISOLATED SHOWERS AND POSSIBLE THUNDERSTORMS MAY DEVELOP EARLY IN THE EVENING HOURS... MAINLY NORTH AND WEST OF NYC. WILL CAP POPS AT 20 PERCENT...AS NOT EXPECTING MANY...IF ANY...STORMS. LATEST HRRR GUIDANCE CONTINUES TO INDICATE SOME SHOWERS...MAINLY WEST OF THE HUDSON RIVER AND INTO INTERIOR PORTIONS OF SW CT. ANY SHOWERS THAT DEVELOP WILL END BETWEEN 9-10 PM. WARM AND HUMID NIGHT ON TAP WITH LOWS IN THE 60S TO LOW 70S. THE WARMEST TEMPS WILL OCCUR IN/AROUND NYC DUE TO THE URBAN HEAT ISLAND EFFECT. SFC DEW POINTS WILL CLIMB THROUGH THE MID 60S AND INTO THE UPPER 60S. CAN EXPECT PATCHY FOG TO DEVELOP AWAY FROM THE CITY. THERE IS A MODERATE RISK OF RIP CURRENTS INTO THIS EVENING WITH ENHANCED SEA BREEZE DEVELOPMENT AND LONG PERIOD SE SWELLS.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
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HOT AND INCREASINGLY HUMID AIR MASS REMAINS OVER THE AREA WEDNESDAY. WITH HIGH PRES DEPARTING AND COLD FRONT APPROACHING FROM THE WEST...SW FLOW INCREASES THROUGHOUT THE DAY...AND SFC DEWPOINTS WILL RISE THROUGH THE 60S AND INTO THE LOWER 70S. MAX TEMPS ON WEDNESDAY 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 COASTS. THE HEAT INDEX ON WEDNESDAY WILL GENERALLY TOP OFF IN THE LOW TO MID 90S...EXPECT 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 CWA...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 PWATS AROUND 2". 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.
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&& .LONG TERM /THURSDAY 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. CONDS 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 /19Z TUESDAY THROUGH SUNDAY/...
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HIGH PRESSURE CONTINUES TO SLOWLY MOVE OFFSHORE. VFR THROUGH MUCH OF THE TAF PERIOD. SEA BREEZE HAVE DEVELOPED THIS AFTERNOON AT KJFK/LGA. THE SEA BREEZE SHOULD REACH KEWR BY 21Z. THIS WILL RESULT IN WIND DIRECTION AROUND 170-180 TRUE BY LATE AFTERNOON. WINDS DIMINISH TONIGHT...WITH MOST SPOTS BECOMING LIGHT AND VARIABLE. SPEEDS INCREASE ONCE AGAIN ON WEDNESDAY. THERE IS A CHANCE OF SOME PATCHY FOG TONIGHT. HAVE INCLUDED SOME TEMPOS FOR REDUCE VSBYS AFTER 08Z. ...NY METRO ENHANCED AVIATION WEATHER SUPPORT... DETAILED INFORMATION...INCLUDING HOURLY TAF WIND COMPONENT FCSTS CAN BE FOUND AT: HTTP://WWW.ERH.NOAA.GOV/ZNY/N90 (LOWER CASE) KJFK FCSTER COMMENTS: TIMING OF SEA BREEZE MAY BE OFF +/- 1 HOUR. KLGA FCSTER COMMENTS: TIMING OF SEA BREEZE MAY BE OFF +/- 2 HOURS. GUSTS MAY BE OCCASIONAL THIS AFTERNOON. KEWR FCSTER COMMENTS: MEDIUM CONFIDENCE IN SEA BREEZE REACHING TERMINAL THIS AFTERNOON. IF IT DOES NOT...WIND DIR WILL STAY CLOSER TO 220 TRUE. KTEB FCSTER COMMENTS: MEDIUM CONFIDENCE IN SEA BREEZE REACHING TERMINAL THIS AFTERNOON. IF IT DOES NOT...WIND DIR WILL STAY CLOSER TO 220 TRUE. KHPN FCSTER COMMENTS: TIMING OF SEA BREEZE MAY BE OFF +/- 2 HOURS. KISP FCSTER COMMENTS: TIMING OF SEA BREEZE MAY BE OFF +/- 1 HOUR. GUSTS MAY BE OCCASIONAL. .OUTLOOK FOR 18Z WED THROUGH SUN... .WED AFTERNOON...PRIMARILY VFR. ISOLATED SHRA/TSTM LATE. .WED NIGHT-THU...SLOW MOVING COLD FROPA. MVFR OR LOWER CONDS IN SCT-NUMEROUS SHOWERS/TSTMS. .THU NIGHT-SAT...VFR. .SUN...CHANCE OF SHOWERS OR THUNDERSTORMS. SUB-VFR POSSIBLE.
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&& .MARINE...
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THE LOCAL ENHANCED SEA BREEZE IS RESULTING IN 15-20 KT WINDS ACROSS NY HARBOR AND THE WESTERN OCEAN WATERS. NOT EXPECTING 25 KT GUSTS...SO WILL NOT HOIST A BRIEF SMALL CRAFT ADVISORY. OTHERWISE...SUB-SCA CONDS EXPECTED THROUGH TONIGHT. PATCHY FOG WILL DEVELOP ON THE WATERS TONIGHT...REDUCING VSBY TO AS LOW AS 1 NM. 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 CONDS THU THROUGH SAT...THEN FCST UNCERTAINTY CREEPS IN BEGINNING ON SUNDAY. HAVE FCST CONTINUED QUIET CONDS...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...
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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.
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&& .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...GOODMAN/MPS NEAR TERM...MPS SHORT TERM...MPS LONG TERM...GOODMAN AVIATION...BC MARINE...GOODMAN/MPS HYDROLOGY...GOODMAN/MPS

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