Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 290946 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 546 AM EDT WED JUL 29 2015 .SYNOPSIS... HIGH PRESSURE BUILDS OFF THE MID ATLANTIC COAST TODAY. A COLD FRONT APPROACHES FROM THE WEST TONIGHT AND THURSDAY MORNING...THEN CROSSES THE TRI-STATE THURSDAY AFTERNOON AND NIGHT. WEAK HIGH PRESSURE BUILDS IN FRIDAY THROUGH SATURDAY. A COLD FRONT APPROACHES SATURDAY NIGHT...WEAKENING AND DISSIPATING WITH ITS ARRIVAL ON SUNDAY. WEAK HIGH PRESSURE FOLLOWS FOR SUNDAY WITH ANOTHER WEAKENING COLD FRONT APPROACHING SUNDAY NIGHT. THIS TOO DISSIPATES WITHIN THE REGION EARLY NEXT WEEK WITH MAIN HIGH PRESSURE STAYING IN THE WESTERN ATLANTIC AND THE MAIN LOW PRESSURE STAYING IN SOUTHEAST CANADA. && .NEAR TERM /THROUGH TONIGHT/... A DEEP LAYERED NORTHERN STREAM RIDGE CONTINUES TO BUILD OVER THE CWA TODAY...WITH THE RIDGE AXIS PASSING OVER THE AREA TONIGHT. SUBSIDENCE UNDER THE RIDGE WILL KEEP THINGS DRY THROUGH TONIGHT. CLOUD COVER WILL ALSO BE AT A MINIMUM...OTHER THAN MAYBE SOME AFTERNOON CUMULUS...UNTIL SOME HIGH CLOUDS BEGIN TO BUILD IN FROM SW TO NE LATE TONIGHT AS THE RIDGE AXIS MOVES TO THE EAST. MAIN STORY TODAY WILL BE THE HEAT...WITH HIGHS MAINLY FROM AROUND 90 TO THE MID 90S...EXCEPT MID TO UPPER 80S ON THE TWIN FORKS OF LONG ISLAND AND COASTAL SE CT. THESE TEMPERATURES COMBINED WITH DEWPOINTS FROM THE MID 60S TO AROUND 70 THIS AFTERNOON WILL PRODUCE HEAT INDICES IN THE 90S...WITH MID-UPPER 90S ACROSS THE NYC METRO AND URBAN PORTIONS OF S CT. BASED ON THIS BEING THE SECOND CONSECUTIVE DAY WITH HEAT INDICES OF 95-99 IN NYC...HAVE CONTINUED THE HEAT ADVISORY THERE. LOWS TONIGHT ARE BASED ON A BLEND OF MAV/ECS/MET GUIDANCE WITH NAM 2-METER TEMPERATURES. READINGS SHOULD BE BETWEEN 5-10 DEGREES ABOVE NORMAL. THERE IS A MODERATE RISK FOR THE METEOROLOGICAL ENHANCEMENT OF RIP CURRENT FORMATION AT ATLANTIC BEACHES INTO THIS EVENING. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... THE DEEP LAYERED NORTHERN STREAM RIDGE EXITS TO THE EAST THURSDAY MORNING...WITH A NORTHERN STREAM TROUGH MOVING IN BEHIND IT THROUGH THURSDAY NIGHT. PRECIPITATION WILL GENERALLY RUN AHEAD OF THE TROUGH...AND NOT TO FAR AHEAD OF ITS ASSOCIATED SURFACE COLD FRONT. CONFIDENCE IN THE OCCURRENCE OF PRECIPITATION HAS LEAD TO AN INCREASE OF POPS TO LIKELY THURSDAY AFTERNOON AND EVENING. ALONG WITH THIS...HAVE ALSO PUT A MENTION OF LOCALLY HEAVY RAINFALL IN THE FORECAST. REFER TO THE HYDROLOGY SECTION OF THE AFD FOR DETAILS ON AMOUNTS AND ANY POTENTIAL IMPACTS. HOWEVER...WITH BUFKIT SOUNDINGS STILL SHOWING SOME WARMING IN THE LAYER FROM AROUND 650-550 HPA...HAVE KEPT THE PROBABILITY OF THUNDER TO CHANCE. MODELS ARE FAIRLY CONSISTENT IN THE TIMING OF THE END OF PRECIPITATION...AND SO EXPECT IT TO COME TO AN END FROM NW TO SE THURSDAY NIGHT AS THE SURFACE COLD FRONT EXITS TO THE EAST. GENERALLY HAVE 1500-2000 J/KG OF SURFACE BASED CAPE FORECAST OVER ALL OF THE CWA BUT THE TWIN FORKS AND THE IMMEDIATE COAST OF SE CT. WITH A BULK SHEAR OF AROUND 30 KT...FAVOR A COMBINATION OF PULSE STORMS AND SOME MULTI-CELLULAR CLUSTERS AND/OR BOWING SEGMENTS. WITH THE REGION FORECAST TO BE IN THE RIGHT REAR QUADRANT OF AN AROUND 80 KT 250 HPA JET...AND THE PASSING OF A 25-30 KT 950-850 JET NEAR/OVER THE AREA THURSDAY AFTERNOON/EVENING...THERE IS SUFFICIENT FORCING TO GO ALONG WITH THE CAPE AND SHEAR FOR STRONG TO POSSIBLY SEVERE STORMS. ACCORDINGLY SPC HAS EXPANDED THE MARGINAL RISK OF SEVERE THUNDERSTORMS TO ENCOMPASS ALL BUT BASICALLY SOUTHERN SUFFOLK COUNTY. WILL MAKE A MINOR ADJUSTMENT TO THIS FOR THE HWO...AND HIGHLIGHT THE SEVERE THREAT FOR ALL BUT EASTERN SUFFOLK COUNTY...NOTING THE LOWER CAPES THERE. FOR HIGHS ON THURSDAY USED A BLEND OF MAV/MET/ECS GUIDANCE WITH NAM 2-METER TEMPERATURES AND A MIX DOWN FROM 975-825 HPA PER BUFKIT SOUNDINGS. HIGHS SHOULD BE AROUND 5 DEGREES COOLER THAN TODAY...AS THE CORE OF THE WARM AIR ALOFT MOVES TO THE EAST WITH THE RIDGE AXIS. FORECAST DEWPOINTS HOWEVER HAVE INCREASED FROM PREVIOUS FORECASTS AND NOW ARE AROUND 70-LOWER 70S. AS A RESULT EXPECT HEAT INDICES MAINLY IN THE LOWER 90S...WITH SOME MID 90S IN NYC/URBAN NE NJ AND THE I-91 CORRIDOR N OF NEW HAVEN. ONLY HAVE A FEW GRIDPOINTS OF HEAT INDICES OF 95 IN NYC PROPER...BUT GIVEN UNCERTAINTIES WITH DEWPOINTS...AND THAT A CHANGE IN 1 DEGREE IN TEMPERATURE AND/OR DEWPOINT MAKES A BIT OF DIFFERENCE IN HEAT INDEX...DO NOT HAVE THE CONFIDENCE TO CANCEL THE HEAT ADVISORY FOR NYC FOR THURSDAY. FOR LOWS THURSDAY NIGHT...A BLEND OF MAV/MET/ECS GUIDANCE AND NAM 2-METER TEMPERATURES WAS USED...WITH VALUES FORECAST TO BE AROUND 5 DEGREES ABOVE NORMAL. && .LONG TERM /FRIDAY THROUGH TUESDAY/... OVERALL FRIDAY INTO NEXT WEEK...NO SIGNIFICANT LARGE SCALE CHANGES WITHIN THE REGION IN THE MID TO UPPER LEVELS. THE MAIN UPPER LEVEL JET STAYS MOSTLY NORTHEAST OF THE REGION WITH THE 250MB HEIGHT GRADIENT GRADUALLY DECREASING GOING INTO NEXT WEEK. THE 500MB HEIGHT IS FORECAST TO GENERALLY STAY BETWEEN 5770M TO 5830M MUCH OF THE PERIOD. THE LOWEST HEIGHTS WILL BE MARKED BY THE THE PASSAGE OF SHORTWAVES WITHIN A LONGWAVE TROUGH OVER THE NORTHEAST. THESE ARE SHOWN TO OCCUR SATURDAY NIGHT INTO EARLY SUNDAY AS WELL AS MONDAY NIGHT INTO TUESDAY. THE LOCAL REGION WILL BE AT THE BASE OF THIS LONGWAVE TROUGH. MUCH OF THE POSITIVE VORTICITY ADVECTION WILL BE LOCATED NORTH OF THE REGION...LEAVING A VOID IN SYNOPTIC FORCING OVER THE LOCAL AREA. THE MID LEVELS WILL LIKEWISE EXHIBIT SIMILAR TRENDS AT THE SURFACE WITH OVERALL A WEAK PRESSURE GRADIENT REMAINING. THE COLD FRONTS APPROACH SATURDAY NIGHT INTO EARLY SUNDAY AND EARLY NEXT WEEK WITH WEAK HIGH PRESSURE FOR OTHER TIME PERIODS WITHIN THE LONG TERM. THE FRONTS DISSIPATE WITHOUT MUCH CHANGE OF AIRMASS FOR THE REGION. THEREFORE...THE POPS FOR SHOWERS AND THUNDERSTORMS WILL IN THE SLIGHT CHANCE RANGE DUE TO TIMING AT NIGHT WITH LESS INSTABILITY AND THE AFOREMENTIONED LACK OF SYNOPTIC FORCING FOR THIS SATURDAY NIGHT. THE POPS ARE ALSO SLIGHT CHANCE FOR EARLY NEXT WEEK DUE TO LARGER UNCERTAINTY BUT WITH SOME MORE INSTABILITY TO WORK WITH POTENTIALLY FOR ANY CONVECTION DURING THE DAY. THE AIRMASS WILL CONTINUE TO BE VERY WARM AND HUMID. MUCH OF THE AREA HAS FORECAST HIGHS OF MID 80S TO NEAR 90 WITH FORECAST LOWS MID 60S TO LOWER 70S. THE DEWPOINTS ARE FORECAST TO STAY WELL WITHIN THE 60S MUCH OF THE TIME PERIOD. && .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/... A WEAK LOW PRESSURE TROUGH WILL REMAIN OVER THE AREA...WHILE HIGH PRESSURE REMAINS TO THE WEST. GENERALLY VFR THIS MORNING...ALTHOUGH A FEW TERMINALS OUTSIDE NYC METRO COULD OBSERVE PATCHY MVFR FOG. KGON COULD GO IFR OR LOWER AS WAS THE CASE LAST NIGHT. EXPECT ANY MVFR OR LOWER CONDITIONS TO QUICKLY IMPROVE TO VFR BY 13Z-14Z. LIGHT AND VARIABLE WINDS THIS MORNING WILL INCREASE TO 5-10 KT BY LATE MORNING/EARLY AFTERNOON FROM THE SW. SPEEDS INCREASE TO AT LEAST 10 KT FOR COASTAL AIRPORTS DURING THE AFTERNOON. ...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: WIND DIRECTION MAY VARY FROM 160-180 IN THE AFTERNOON. KLGA FCSTER COMMENTS: TIMING OF ONSET OF SOUTH WINDS MAY VARY BY 1-2 HOURS...AND DIRECTION MAY VARY FROM 160-180. KEWR FCSTER COMMENTS: WIND DIRECTION MAY VARY FROM 180-210 IN THE AFTERNOON. THE AFTERNOON KEWR HAZE POTENTIAL FORECAST IS GREEN...WHICH IMPLIES SLANT RANGE VISIBILITY 7SM OR GREATER OUTSIDE OF CLOUD. KTEB FCSTER COMMENTS: WIND DIRECTION MAY VARY FROM 180-210 IN THE AFTERNOON. KHPN FCSTER COMMENTS: WIND DIRECTION MAY VARY FROM 170-200 IN THE AFTERNOON. KISP FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. .OUTLOOK FOR 06Z THU THROUGH SUNDAY... .WED NIGHT...MVFR VSBY POSSIBLE LATE. .THU...EARLY MORNING HAZE WITH MVFR CONDITIONS...THEN SCT AFTERNOON/EVENING TSTMS WITH MVFR OR LOWER CONDITIONS. .FRI-SUNDAY...VFR. && .MARINE... A WEAK TO MODERATE STRENGTH PRESSURE GRADIENT WILL GENERALLY KEEP WINDS AT 15 KT OR LESS THROUGH THURSDAY NIGHT. HOWEVER...COULD SEE A COMBINATION OF THE TIGHTENING OF THE PRESSURE GRADIENT AHEAD OF A COLD FRONT AND THE SEABREEZE BRING WINDS TO 20 KT IN THE NY BIGHT REGION THURSDAY AFTERNOON/EVENING. FOR NOW IT APPEARS THOUGH THAT ANY GUSTS TO 25 KT IN THIS REGION WILL BE OCCASIONAL AT MOST. GIVEN THIS...AND CURRENT EXPECTATION OF NO SIGNIFICANT SWELL THROUGH THURSDAY NIGHT...EXPECT SEAS TO REMAIN BELOW 5 FT THROUGH THURSDAY NIGHT ALSO. SUB SCA CONDITIONS ARE FORECAST ON FRIDAY AND FRIDAY NIGHT WITH WEAK HIGH PRESSURE MOVING ACROSS. THE BELOW SCA CONDITIONS ARE FORECAST TO CONTINUE INTO MUCH OF SATURDAY UNTIL SOME HIGHER SEAS FROM CONTINUED SOUTHERLY FETCH WILL MOVE IN LATE SATURDAY AFTERNOON THROUGH SUNDAY. OCEAN SEAS ARE FORECAST TO REACH 5 TO 7 FT WITH THIS FETCH...SO SCA POTENTIAL WILL BE THERE. && .HYDROLOGY... DRY THROUGH TONIGHT. AROUND 1/4-1/2 INCH OF BASIN AVG RAINFALL IS POSSIBLE THURSDAY AND THURSDAY NIGHT. HOWEVER...WITH PRECIPITABLE WATERS FORECAST TO OVER 2 INCHES THURSDAY AFTERNOON AND EVENING...LOCALLY HEAVY RAINFALL IS POSSIBLE WITH ANY STRONGER CONVECTION. IF THIS OCCURS...THEN MINOR URBAN/POOR DRAINAGE FLOODING WOULD BE POSSIBLE. NO SIGNIFICANT WIDESPREAD RAIN EXPECTED FRIDAY THROUGH TUESDAY. && .CLIMATE... RECORD HIGHS FOR WEDNESDAY JULY 29 2015... LOCATION..........RECORD HIGH/YEAR.........FORECAST HIGH NEWARK....................100/1949.................96 BRIDGEPORT.................96/2002.................90 CENTRAL PARK...............99/1949.................94 LAGUARDIA..................97/1949.................95 KENNEDY....................99/2002.................91 ISLIP......................96/2002.................91 && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...HEAT ADVISORY UNTIL 8 PM EDT THURSDAY FOR NYZ072>075-176-178. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...MALOIT/JM NEAR TERM...MALOIT SHORT TERM...MALOIT LONG TERM...JM AVIATION...DW MARINE...MALOIT/JM HYDROLOGY...MALOIT/JM CLIMATE...

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