Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 211948 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 348 PM EDT MON JUL 21 2014 .SYNOPSIS...
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HIGH PRESSURE REMAINS OVER THE AREA THROUGH TONIGHT...THEN SLIDES OFFSHORE ON TUESDAY. A COLD FRONT WILL MOVE INTO THE NORTHEAST WEDNESDAY...THEN SLOWLY MOVE ACROSS THE AREA THROUGH THURSDAY. HIGH PRESSURE WILL FOLLOW FROM THURSDAY NIGHT INTO THE WEEKEND. ANOTHER LOW PRESSURE SYSTEM WILL APPROACH FOR THE BEGINNING OF NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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NO MAJOR UPDATES MADE TO THE LATEST FORECAST. A FEW CUMULUS HAVE DEVELOPED ACROSS PORTIONS OF NJ...SOUTHEAST NY...NYC AND WESTERN CT AS MOISTURE LINGERS BENEATH A 750-600 HPA RIDGE. THE SEA BREEZE IS GRADUALLY MOVING INLAND ACROSS LONG ISLAND...WITH WINDS SHIFTING TO SOUTHERLY IN ITS WAKE. ALOFT...AN UPPER TROUGH IS EXITING THE COAST WITH RIDGING BUILDING IN ITS WAKE. SUBSIDENCE WILL GENERALLY HINDER ANY SHOWER DEVELOPMENT...MAINTAINING DRY CONDITIONS ACROSS THE AREA. LOW TEMPERATURES IN THE 60S /CLOSE TO CLIMATOLOGICAL NORMAL/ CAN BE EXPECTED.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
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SUBSIDENCE OWING TO A BUILDING RIDGE WILL MAINTAIN DRY CONDITIONS THROUGH TUESDAY MORNING. BY AFTERNOON...UPPER LEVEL HEIGHT FALLS AND CONVERGENCE ALONG A SUBTLE SURFACE TROUGH WILL LEAD TO A SLIGHT CHANCE OF THUNDERSTORMS ACROSS NORTHERN NJ...SOUTHEAST NY AND WESTERN CT. ALTHOUGH SURFACE-BASED CAPE VALUES ARE FORECAST AROUND 500-1000 J/KG...DEEP LAYER FLOW AVERAGING LESS THAN 15KT WILL KEEP STORMS SUB-SEVERE. HOWEVER...BRIEF GUSTY WINDS NEAR THUNDERSTORMS ARE POSSIBLE GIVEN DRIER AIR/SUPER ADIABATIC LAPSE RATES BENEATH 5000 FT. RIDGING ALOFT AND SOUTHWEST FLOW WILL LEAD TO HIGH TEMPERATURES NEAR OR A FEW DEGREES ABOVE CLIMATOLOGICAL NORMALS FOR TUESDAY.
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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ATTENTION MID WEEK WILL BE FOCUSED ON THE PROGRESSION OF A SLOW MOVING COLD FRONT ACROSS THE NORTHEAST. GENERALLY DECENT MODEL AGREEMENT BETWEEN THE 12Z MODEL SUITE...MINUS THE ECMWF...ON THE TIMING OF THE FRONT REACHING THE AREA OVERNIGHT WED. THE FRONT THEN LOOKS TO STALL JUST OFFSHORE...WITH A SFC LOW THEN FORMING AND RIDING THE FRONT THURS...BRINGING ANOTHER CHC OF PCPN DURING THE DAY THURS...EVENTUALLY TAPERING OFF THURS NIGHT AS HIGH PRESSURE BUILDS IN BEHIND THE FRONT. BEGINNING WED DURING THE DAY...SFC LOW TREKKING THROUGH SOUTHERN CANADA WILL DRAG THE ASSOCIATED COLD FRONT THROUGH THE GREAT LAKES...EVENTUALLY HAVING THE FRONT NEAR SOUTHERN NEW ENGLAND BY 00Z THURS. STRONG WAA OUT AHEAD OF THE FRONT WILL LOOK TO INJECT IN A VERY WARM...MOIST ATMO. MULTIPLE WEAK VORT MAXES WILL MOVE THROUGH THE NORTHEAST THROUGHOUT THE DAY OUT AHEAD OF THE MAIN UPPER LVL TROUGH...WHICH COMBINING WITH DECENT INSTABILITY AND MARGINAL SHEAR COULD PRODUCE AN ISO TSTM OVER AREAS WELL NORTH AND WEST OF NYC METRO. WHILE THE SVR THREAT LOOKS TO REMAIN NORTH OF THE AREA...CANNOT RULE OUT A STRONGER STORM OVER LOWER HUDSON AND INTERIOR SW CT AREAS. THE MAIN PCPN EVENT FOR THE AREA WILL THEN BE AS THE COLD FRONT SWINGS THROUGH WED NIGHT. EXPECTING THE THREAT FOR THUNDER TO DIMINISH OVERNIGHT WITH LOSS OF INSTABILITY/HEATING...SO THINKING THE THREAT WILL TURN MORE TO HEAVY RAIN AND POTENTIAL FOR FLOODING WITH PWATS HITTING AROUND 2 INCHES. POSSIBLE BREAK IN THE PCPN EARLY THURS...THEN ANOTHER ROUND DURING THE DAY AS THE AFOREMENTIONED SFC LOW FORMS ALONG THE FRONT AND PUSHES TO THE NORTHEAST AND EAST. MINIMAL INSTABILITY THURS WILL KEEP A LOWER CHC THREAT FOR TSTMS...MAINLY OVER LI AND TO THE SOUTH. WILL MAINTAIN CHC POPS FOR NOW WITH UNCERTAINTY ON THE EXACT TIMING OF THE PCPN. PCPN TAPERS OFF THURS NIGHT AS FRONT EXITS THE REGION AND SFC HIGH BUILDS IN FROM THE WEST. MUCH COOLER AND DRIER AIRMASS MOVES IN BEHIND THE FRONT FOR FRI AS THE REGION SITS BETWEEN THE DEPARTING UPPER LVL TROUGH AND RIDGING OVER THE CENTRAL US...RESULTING IN DRY AND MOSTLY SUNNY SKIES. EXPECT THE DRY WX TO CONTINUE THROUGH SAT. SOME MODEL DISCREPANCY THEN SUNDAY INTO THE BEGINNING OF NEXT WEEK WITH THE HANDLING OF THE NEXT LOW PRESSURE SYSTEM. 00Z ECMWF WAS THE MORE PROGRESSIVE OF THE SOLUTIONS PUSHING THE LOW THROUGH SUN NIGHT INTO MON. HOWEVER... THE 12Z MODEL SUITES A BIT SLOWER IN HOLDING THE LOW BACK OVER THE GREAT LAKES. WITH THE UNCERTAINTY...MAINTAINED THE PREVIOUS THINKING OF CHC POPS FOR THE PERIOD FOR NOW UNTIL THE MODELS COME INTO BETTER AGREEMENT. AS MENTIONED...STRONG SURGE OF WARM AIR WED WILL PUSH TEMPS WELL ABOVE NORMAL...WITH SOME SPOTS OF NYC METRO POTENTIALLY EVEN HITTING 90. THE ONSHORE FLOW WILL ALLOW FOR IMMEDIATE COASTAL AREAS TO HOVER IN LOWER-MID 80S. TEMPS WILL THEN DROP THURS AND FRI TO A FEW DEGREES BELOW NORMAL...EVENTUALLY REBOUNDING TO NORMAL LEVELS FOR THE WEEKEND.
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&& .AVIATION /19Z MONDAY THROUGH SATURDAY/...
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SURFACE RIDGE HAS SHIFTED A LITTLE TOWARD THE COAST...AND HAS BEEN DELAYING SEA BREEZE INITIATION. IT ARRIVED AT KJFK A LITTLE AFTER 17Z...AND BASED ON ITS FORWARD PROGRESS PER LOCAL RADARS LOOKS TO ARRIVE AT KLGA/KEWR/KTEB BETWEEN 21Z-22Z. THE 21Z SCHEDULED AMD WILL FINE TUNE THIS TIMING. VFR WITH LIGHT S-SW FLOW TONIGHT AT MOST TERMINALS. OUTLYING TERMINALS COULD HAVE MVFR VSBY LATE TONIGHT INTO THE EARLY DAYLIGHT HOURS....AND KGON COULD FLUCTUATE BETWEEN MVFR AND IFR LATE TONIGHT AS IT OFTEN DOES AT THIS TIME OF YEAR UNDER A MOSTLY CLEAR SKY WITH LIGHT ONSHORE FLOW. VFR AFTER 12Z TUE...WITH A BETTER CHANCE FOR SEA BREEZE DEVELOPMENT AT THE USUAL TIMES...15Z KBDR/KGON...16Z JFK...AND 18Z AT KISP. 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: HIGH CONFIDENCE. KLGA FCSTER COMMENTS: TIMING OF WIND SHIFT TO THE S MAY BE OFF BY AN HOUR. KEWR FCSTER COMMENTS: TIMING OF WIND SHIFT TO THE SE-S MAY BE OFF BY AN HOUR. KTEB FCSTER COMMENTS: TIMING OF WIND SHIFT TO THE SE-S MAY BE OFF BY AN HOUR. KHPN FCSTER COMMENTS: TIMING OF WIND SHIFT TO THE SE-S MAY BE OFF BY AN HOUR OR TWO. KISP FCSTER COMMENTS: TIMING OF WIND SHIFT TO THE SE-S MAY BE OFF BY AN HOUR OR TWO. .OUTLOOK FOR 18Z TUE THROUGH FRI... .TUE AFTERNOON-WED...PRIMARILY VFR. ISOLATED TSTM NW OF THE NY METRO LATE BOTH DAYS. .WED NIGHT-THU...SLOW MOVING COLD FROPA. BRIEF MVFR OR LOWER CONDS IN SCT-NUMEROUS SHOWERS/TSTMS. .FRI-SAT...VFR.
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&& .MARINE...
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A RELAXED PRESSURE GRADIENT WILL KEEP WINDS TO 15 KT OR LESS AND SEAS 4 FT OR LESS ON THE OCEAN WATERS AND 1 FT OR LESS ON THE REMAINDER OF THE WATERS AROUND LONG ISLAND THROUGH TUESDAY. TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...WINDS AND SEAS WILL INCREASE APPROACHING SMALL CRAFT ADVISORY LEVELS OF 25 KT AND 5 FT SEAS WED AFTERNOON AND NIGHT. STRONG SW FLOW WED-WED NIGHT AHEAD OF THE COLD FRONT COULD SEE OCNL GUSTS UP TO 25 KTS...AND SHOULD SEE SEAS AROUND 5 FT ON THE OCEAN WATERS. ONCE THE FRONT PASSES THURS...HIGH PRESSURE BUILDS IN...ALLOWING FOR SUB-SCA CONDITIONS TO FORM ACROSS ALL WATERS BY THURS NIGHT. SUB-SCA CONDITIONS THEN LAST THROUGH THE COMING WEEKEND.
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&& .HYDROLOGY... DRY INTO TUESDAY MORNING...THEN ISOLD CONVECTION COULD BRING LOCALIZED AMOUNTS UP TO A FEW TENTHS OF AN INCH TUESDAY AFTERNOON/EVENING MAINLY TO AREAS N/W OF NYC. LATE WED THROUGH THU WILL BE THE NEXT CHC OF A SIGNIFICANT RAINFALL WITH THE POTENTIAL FOR 1/4 TO 1/2 INCH WITH THE APPROACH OF A SLOW MOVING COLD FRONT. A FEW HEAVY SHOWERS AND TSTMS COULD PRODUCE BRIEF HEAVY DOWNPOURS WITH ISOLATED AMOUNTS OF UP TO AROUND 1 INCH. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...MMD/SEARS NEAR TERM...MMD SHORT TERM...MMD LONG TERM...SEARS AVIATION...GOODMAN MARINE...GC/MALOIT HYDROLOGY...GC/MALOIT

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