Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 231446 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 1046 AM EDT WED JUL 23 2014 .SYNOPSIS... AS HIGH PRESSURE MOVES EAST OF THE AREA...A COLD FRONT WILL MOVE SLOWLY EAST AND PASS EAST OF THE AREA ON THURSDAY. HIGH PRESSURE WILL FOLLOW FRIDAY THROUGH SATURDAY. WAVES OF LOW PRESSURE THEN PASS NEAR THE REGION SUNDAY INTO MONDAY FOLLOWED BY A COLD FRONT MONDAY NIGHT INTO TUESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... FORECAST UPDATED WITH JUST MINOR ADJUSTMENTS TO REFLECT LATEST OBSERVATIONS. SOUTHWEST WINDS BETWEEN A DEPARTING OFFSHORE HIGH PRES SYSTEM AND AN APPROACHING COLD FRONT WILL CONTINUE TO ADVECT WARM MOIST UNSTABLE MARITIME TROPICAL AIR ACROSS THE AREA. EXPECT A HAZY...HOT AND HUMID SUMMER DAY FOLLOWED BY STRONG TO POTENTIALLY SEVERE THUNDERSTORMS MAINLY AFTER 3 PM WEST AND NORTH OF NYC. HIGH TEMPS IN THE LOWER 90S COMBINED WITH DEW POINTS APPROACHING 70 DEGREES WILL PRODUCE HEAT INDEX VALUES IN THE MID 90S ACROSS URBAN AREAS OF NYC AND NORTHEAST NJ THIS AFTERNOON. BECAUSE A COLD FRONT IS FORECAST TO MOVE SOUTH OF THE AREA THU PRODUCING COOLER TEMPS...WE WILL NOT MEET THE 2 DAY HEAT CRITERIA OF 95 DEGREES AND THEREFORE WILL NOT ISSUE A HEAT ADVISORY FOR NYC. BECAUSE BOTH SFC AND LOW LEVEL BASED INSTABILITY WILL BE INCREASING ALONG AND AHEAD OF A DEVELOPING PRE FRONTAL TROUGH...THERE WILL BE AN INCREASING POTENTIAL FOR SEVERE TSTMS...MAINLY WEST AND NORTH OF NY AFT 19Z. WITH A FCST MEAN STORM MOTION OF 230 DEGREES AT 15 KTS...CAN NOT RULE OUT TRAINING OF STORMS ACROSS THE SAME AREA WITH AN ADDED POTENTIAL FOR ISOLATED FLASH FLOODING. STAY TUNED. THERE IS A MODERATE RISK OF RIP CURRENTS...MAINLY THIS AFTERNOON THROUGH EVENING WITH ENHANCED SEA BREEZE DEVELOPMENT. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... TONIGHT...SHOWERS AND TSTMS WILL GRADUALLY WEAKEN AS THEY MOVE INTO A MORE STABLE MARINE ENVIRONMENT IN PLACE ACROSS LONG ISLAND AND SOUTHERN CT. THURSDAY...WITH MOST MODELS FORMING A WAVE OF LOW PRESSURE ALONG THE SAGGING BOUNDARY...LOOK FOR THE REDEVELOPMENT OF A STRATIFORM RAIN SHIELD WITH EMBEDDED CONVECTION FOCUSED ACROSS THE COASTAL AREA THROUGH AT LEAST THE EARLY AFTERNOON HOURS. THE LATEST RAINFALL AMOUNTS MIGHT BE UNDER ESTIMATED. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... THE PERIOD BEGINS WITH THE COLD FRONT SLOWLY MAKING ITS WAY FARTHER TO OUR E/SE. AS SUCH...POPS WILL CONTINUE DIMINISHING WITH ALL AREAS DRY BY LATE THURSDAY NIGHT. HIGH PRESSURE BUILDS ACROSS THE AREA FOR FRIDAY...YIELDING DRY WEATHER AND TEMPS NEAR TO A COUPLE DEGREES BELOW SEASONAL NORMS. SATURDAY WILL SEE SIMILAR TEMPERATURES WITH MOISTURE STARTING TO INCREASE ACROSS THE AREA ONCE AGAIN. ZONAL FLOW WILL BE PRESENT ALOFT...AND WITH A SUBTLE/WEAK SHORTWAVE PASSING NEAR THE AREA...CONTINUED WITH SLIGHT CHANCE POPS ACROSS WESTERN PORTIONS OF THE CWA. WEAK FORCING WILL LEAD TO MOST SPOTS STAYING DRY THOUGH. THE UPPER-LEVEL PATTERN ACROSS THE CONUS REALLY STARTS TO AMPLIFY SATURDAY NIGHT INTO SUNDAY...AS A STOUT SHORTWAVE DROPS OUT OF THE SOUTHERN CANADIAN PRAIRIES AND INTO THE MIDWEST. AS IT PROPAGATES AROUND THE UPPER LOW CENTERED ACROSS NORTHERN QUEBEC...A DEEP TROUGH WILL BE CARVED OUT ACROSS THE EASTERN US. THIS WILL SET THE STAGE FOR A PERIOD OF UNSETTLED WEATHER SUNDAY INTO MONDAY...AS STRENGTHENING JET DYNAMICS ALOFT ALLOW FOR A COUPLE WAVES OF LOW PRESSURE TO PASS NW OF THE AREA. WITH INCREASING SOUTHERLY FLOW/MOISTURE ACROSS THE AREA...SHOWERS AND STORMS WILL BECOME MORE LIKELY. STILL...SIGNIFICANT TIMING DIFFERENCES EXIST IN THE PASSAGE OF SHORTWAVES/BETTER DYNAMICS ALOFT...WHICH LEADS TO CONTINUED UNCERTAINTY IN THE TIMING OF MORE WIDESPREAD PRECIPITATION. WILL GO WITH HIGHER-END CHANCE POPS SUNDAY THROUGH MONDAY AS A RESULT. THE ATTENDANT SURFACE COLD FRONT THEN LOOKS TO PUSH THROUGH MONDAY NIGHT INTO TUESDAY...WITH CONDITIONS SLOWLY DRYING OUT. THERE IS A GOOD AMOUNT OF UNCERTAINTY WITH THE FRONTAL TIMING AS WELL...AS THE 23/00Z ECMWF SHOWS IT STALLING ACROSS THE AREA WITH PRECIP LINGERING ACROSS EASTERN AREAS INTO TUESDAY NIGHT. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... A COLD FRONT APPROACHES FROM THE WEST TODAY...THEN CROSSES THE TRI-STATE TONIGHT. MORNING TAFS REMAIN ON TRACK...SO NO SIGNIFICANT CHANGES MADE TO THE PREVIOUS TAF PACKAGE. WILL CONVERT PROB30 GROUPS AT 23Z TO TEMPO GROUPS FOR CONVECTION AT KNYC METRO TERMINALS. 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. HAVE ADDED WNW WINDS 15G30 KT WITH THE TSTMS FOR CITY TERMINALS. 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 TONIGHT. ...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 CHANGES IN WIND SPEED/DIRECTION COULD BE OFF +/- 2-3 HOURS. MODERATE CHANCE OF OCCASIONAL GUSTS OF 20-25 KT WITH SEABREEZE THIS AFTERNOON. ISOLD SHRA/TSTM POSSIBLE 19-23Z. KLGA FCSTER COMMENTS: TIMING OF CHANGES IN WIND SPEED/DIRECTION COULD BE OFF +/- 2-3 HOURS. MODERATE CHANCE OF OCCASIONAL GUSTS OF 20-25 KT WITH SEABREEZE THIS AFTERNOON. SCT SHRA/TSTM POSSIBLE 19-23Z. KEWR FCSTER COMMENTS: TIMING OF CHANGES IN WIND SPEED/DIRECTION COULD BE OFF +/- 2-3 HOURS. MODERATE CHANCE OF OCCASIONAL GUSTS OF 15-20 KT WITH SEABREEZE THIS AFTERNOON. SCT SHRA/TSTM POSSIBLE 19-23Z. THE AFTERNOON KEWR HAZE POTENTIAL FORECAST IS YELLOW...WHICH IMPLIES SLANT RANGE VISIBILITY 4-6SM OUTSIDE OF CLOUD. KTEB FCSTER COMMENTS: TIMING OF CHANGES IN WIND SPEED/DIRECTION COULD BE OFF +/- 2-3 HOURS. LOW CHANCE OF OCCASIONAL GUSTS OF 15-20 KT WITH SEABREEZE THIS AFTERNOON. SCT SHRA/TSTM POSSIBLE 19-23Z. KHPN FCSTER COMMENTS: TIMING OF CHANGES IN WIND SPEED/DIRECTION COULD BE OFF +/- 2-3 HOURS. LOW CHANCE OF OCCASIONAL GUSTS OF 15-20 KT WITH SEABREEZE THIS AFTERNOON. SCT SHRA/TSTM POSSIBLE 19-23Z. KISP FCSTER COMMENTS: TIMING OF CHANGES IN WIND SPEED/DIRECTION COULD BE OFF +/- 2-3 HOURS. MODERATE CHANCE OF OCCASIONAL GUSTS OF 20-25 KT WITH SEABREEZE THIS AFTERNOON. ISOLD SHRA/TSTM POSSIBLE 23-03Z. .OUTLOOK FOR 12Z THURSDAY THROUGH SUNDAY... .THURSDAY...MVFR OR LOWER CONDITIONS IN SCT-NUMEROUS SHRA/TSTMS AND POSSIBLE FOG. BEST CHANCE IN AFTERNOON OVER EASTERN TERMINALS. .THURSDAY NIGHT-SATURDAY MORNING...VFR. .SATURDAY AFTERNOON...MVFR OR LOWER POSSIBLE IN ISOLD SHRA/TSTM MAINLY NW OF NYC. .SATURDAY NIGHT-SUNDAY...CHANCE OF SHRA/TSTMS WITH MVFR OR LOWER POSSIBLE. && .MARINE... THIS AFTERNOON THROUGH THIS EVENING...WINDS AND SEAS WILL APPROACH SMALL CRAFT ADVISORY LEVELS OF 25 KNOTS AND 5 FEET AS A COLD FRONT MOVES EAST TOWARD THE AREA. SOUTHWEST WINDS WILL INCREASE TO 10 TO 15 KNOTS WITH GUSTS TO 20 KNOTS DURING THIS TIME. ISOLATED WIND GUSTS UP TO 25 KNOTS CAN NOT BE RULED OUT. GUSTY WINDS ARE ALSO POSSIBLE IN AND AROUND TSTMS MAINLY FROM SANDY HOOK NJ EAST ACROSS THE COASTAL WATERS DURING THIS TIME. SATURDAY NIGHT THROUGH SUNDAY...INCREASING SOUTH WINDS AND BUILDING SEAS WILL ONCE AGAIN APPROACH SMALL CRAFT ADVISORY LEVELS WITH THE APPROACH OF LOW PRESSURE. OTHERWISE...WINDS AND SEAS WILL REMAIN TRANQUIL. && .HYDROLOGY... THIS AFTERNOON THROUGH THURSDAY...1/4 TO 1/2 INCH OF RAIN IS FORECAST WITH THE APPROACH OF A COLD FRONT. AS THE PRECIPITABLE WATER CONTENT INCREASES TO AROUND 2 INCHES...BASED ON A SLOW MEAN FLOW OF AROUND 15 KNOTS...A FEW STORMS MIGHT MOVE ACROSS TH SAME AREA AND PRODUCE FLASH FLOODING WITH ISOLATED AMOUNTS OF 1.0 TO 1.5 INCHES. WAVES OF LOW PRESSURE PASSING NEAR THE AREA SUNDAY INTO MONDAY HAVE THE POTENTIAL TO PRODUCE SHOWERS AND STORMS CAPABLE OF HEAVY RAIN. BECAUSE SIGNIFICANT UNCERTAINTY STILL EXISTS WITH THE TIMING AND AMOUNTS...THIS HEAVY RAIN POTENTIAL WILL NOT BE INCLUDED IN THE HAZARDOUS WEATHER OUTLOOK AT THIS TIME. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$ SYNOPSIS...GC/PICCA NEAR TERM...BC/GC/PICCA SHORT TERM...GC LONG TERM...PICCA AVIATION...MALOIT/MPS MARINE...GC/PICCA HYDROLOGY...GC/PICCA

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