Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 271820 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 220 PM EDT WED MAY 27 2015 .SYNOPSIS... HIGH PRESSURE WILL MOVE TO THE EAST THIS AFTERNOON. A COLD FRONT WILL APPROACH FROM THE WEST TONIGHT...MOVE ACROSS THE AREA ON THURSDAY...THEN SLIDE TO THE SOUTH THURSDAY NIGHT. MEANWHILE...HIGH PRESSURE WILL REMAIN OFF THE ATLANTIC COAST. STRONGER COLD FRONT WILL THEN IMPACT THE AREA FROM SUNDAY INTO EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... SVR TSTM WATCH 227 IN EFFECT UNTIL 7 PM FOR ALL AREAS NORTH/WEST OF NYC. LINE OF TSTMS OVER ERN PA WILL MOVE INTO THE AREA LATE THIS AFTERNOON AND THIS EVENING...AND INTENSIFY AS IT ENCOUNTERS UNSTABLE AIR MASS WITH MLCAPE 1000-1500 J/KG OVER NRN NJ AND THE LOWER HUDSON VALLEY...WITH MID LEVEL SHORTWAVE AND LEE TROUGH PROVIDING LIFT/LOW LEVEL CONVERGENCE. EARLIER HRRR ALSO INDICATED POTENTIAL FOR SCT DISCRETE CELLS OUT AHEAD OF THE LINE. STRONGER CELLS/BOWING LINE SEGMENTS HAVE POTENTIAL FOR DAMAGING WIND GUSTS AND MARGINALLY LARGE HAIL. WITH CORFIDI VECTORS 10 KT OR LESS AND PRECIP EFFICIENCY OVER 1.5 INCHES...WILL ALSO HAVE TO WATCH FOR POTENTIAL FOR TRAINING OF CELLS WITH LOCALLY HEAVY RAINFALL OF 1-2 INCHES. BIG QUESTION IS HOW FAR AND HOW STRONG THESE STORMS WILL SURVIVE INTO THE MARINE LAYER IN PLACE OVER NYC...LONG ISLAND AND MOST OF SRN CT. ATTM THINK STRONGEST STORMS WILL WEAKEN BELOW SVR LIMITS AS THEY APPROACH THE ERN EDGE OF THE WATCH AREA TOWARD EVENING... BUT DEPENDING ON LATER TRENDS IT IS POSSIBLE THE WATCH MAY HAVE TO BE LOCALLY EXTENDED INTO COUNTIES JUST TO ITS EAST INCLUDING NEW HAVEN CT...ALL OF NYC...AND NASSAU COUNTY. IT STILL APPEARS THAT THE REST OF LONG ISLAND AND SOUTHERN CT WILL BE TOO STABLE IN THE LOW LEVELS FOR ORGANIZED CONVECTION DUE TO MARINE INFLUENCE...BUT HAVE CARRIED SLIGHT CHANCE POP FOR ANY WEAKENING CONVECTION THAT DRIFTS INTO THESE AREAS LATER TONIGHT. AFTER DAYTIME HIGHS 80-85 FROM NYC NORTH/WEST...IN THE 70S MOST ELSEWHERE...AND ONLY UPPER 60S FOR THE SOUTH SHORES OF ERN LONG ISLAND AND SE CT...SHOULD SE A HUMID NIGHT WITH LOWS IN THE 60S. THERE IS SOME POTENTIAL FOR PATCHY FOG LATE TONIGHT NORTH/WEST OF NYC WHERE HEAVIER RAIN FALLS. NOTING THAT FOG HAS NOT MATERIALIZED THE PAST FEW NIGHTS...STILL DO NOT HAVE THE CONFIDENCE TO MENTION. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... MODELS DIFFER ON COVERAGE/EXTENT OF CONVECTION WITH A COLD FRONT ON THURSDAY. ALSO DIFFER ON TIMING WITH THE GFS/ECMWF FASTER THAN THE NAM/CMC-REG. NOTING 700-500 HPA FLOW HAS A FAIRLY DECENT PERPENDICULAR COMPONENT TO THE FRONT...LEANED TOWARDS THE FASTER TIMING OF THE GFS/ECMWF FOR POPS. WITH A WEAKENING FRONT THOUGH...DID NOT FEEL COMFORTABLE GOING WITH HIGHER THAN CHANCE POPS AT THIS TIME. PROBABILITIES ARE GENERALLY HIGHER FROM NYC AND AREAS JUST NORTH/WEST. WITH LESS MLCAPE...500-1000 J/KG OVER THE INTERIOR THAN TODAY...AND THE BEST DYNAMIC FORCING FORECAST TO THE N OF THE REGION...DO NOT THINK THERE IS AS MUCH OF A THREAT FOR SEVERE WEATHER. THOUGH AN ISOLATED STRONG TO SEVERE STORM OR TWO CANNOT BE COMPLETELY RULED OUT. HIGHS ON THU SHOULD BE IN THE 80S INLAND...AND IN THE 70S NEAR THE COAST...MAINLY PER WARMER NAM MOS GUIDANCE. WOULD NOT BE SURPRISING IF A FEW LOCATIONS IN NE NJ APPROACHED 90. DEWPOINTS ON THURSDAY SHOULD BE A TAD LOWER THAN TODAY...MAINLY IN THE LOWER 60S. A WEAK COLD FRONT WILL MOVE ACROSS THURSDAY NIGHT. LITTLE TO NO PRECIPITATION IS EXPECTED WITH THE FRONT. LOWS SHOULD BE IN THE 60S IN MOST PLACES...EXCEPT MID/UPPER 50S IN THE VALLEYS WELL NORTH/WEST OF NYC. && .LONG TERM /FRIDAY THROUGH TUESDAY/... HEIGHTS BUILD ALOFT FRIDAY INTO SATURDAY. ANY CONVECTION FRIDAY OR SATURDAY WILL BE ISOLATED...DIURNAL IN NATURE...AND LIKELY WELL INLAND. WILL KEEP THE FORECAST DRY FOR NOW. MAIN QUESTION IN THE LONG TERM WILL COME DURING THE SECOND HALF OF THE WEEKEND AND START OF THE NEW WEEK AS A COLD FRONT APPROACHES. THE 00Z OPERATIONAL GFS STILL REMAINS THE FASTER AND MORE MORE AGGRESSIVE SOLUTION. WILL CONTINUE TO RUN WITH THE SLIGHTLY SLOWER 00Z ECMWF...WHICH DOES NOT BRING THE FRONT THROUGH UNTIL SUNDAY AFTERNOON/NIGHT. WILL CONTINUE TO INTRODUCE SOME LOW CHANCE POPS LATE SATURDAY AFTERNOON AND NIGHT AS SOME SHOWERS AND THUNDERSTORMS COULD DEVELOP OUT AHEAD OF THE FRONT ITSELF. BOTH MODEL SOLUTIONS KEEP THE FRONT IN THE VICINITY OF THE FORECAST AREA INTO EARLY NEXT WEEK...RESULTING IN CHANCE POPS FOR MONDAY AND TUESDAY. THERE IS THE POTENTIAL FOR AN ORGANIZED RAINFALL EVENT LATE IN THE WEEKEND INTO EARLY NEXT WEEK AS THE COLD FRONT MOVES INTO THE AREA. CONDITIONS WILL REMAIN UNSEASONABLY WARM THROUGH SAT...THEN COOLS DOWN SUNDAY INTO MONDAY BEHIND THE COLD FRONT. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... A WEAK COLD FRONT WILL APPROACH THE REGION TONIGHT AND PASS ACROSS THURSDAY. ANY STRATUS WILL GIVE WAY TO VFR CONDITIONS FOR THE REMAINDER OF THE AFTERNOON OUTSIDE OF AN THUNDERSTORMS. BEST CHANCE FOR THUNDER AFTER 20Z AT KEWR/KTEB AND KSWF. THUNDER WOULD WEAKEN AS IT MOVES EAST LATE THIS AFTERNOON AND THIS EVENING. RETURN TO STRATUS AND FOG EXPECTED TONIGHT. BETTER CHANCE EAST OF NYC METRO. IFR TO LIFR POSSIBLE LATE TONIGHT. ANY STRATUS SHOULD CLEAR THURSDAY MORNING. SOUTH TO SOUTHWEST WINDS CONTINUE THROUGH THE TAF PERIOD. SPEEDS DIMINISH 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: LOW PROB FOR THUNDER AFTER 21-22Z. GENERALLY EXPECT ANY THUNDERSTORMS TO WEAKEN AS THEY TRACK TOWARD THE AIRPORT. KLGA FCSTER COMMENTS: LOW PROB FOR THUNDER AFTER 21-22Z. GENERALLY EXPECT ANY THUNDERSTORMS TO WEAKEN AS THEY TRACK TOWARD THE AIRPORT. KEWR FCSTER COMMENTS: MEDIUM PROB FOR THUNDER AFTER 20-21Z. STORMS SHOULD WEAKEN AS THEY APPROACH THE AIRPORT. KTEB FCSTER COMMENTS: MEDIUM PROB FOR THUNDER AFTER 20-21Z. STORMS SHOULD WEAKEN AS THEY APPROACH THE AIRPORT. KHPN FCSTER COMMENTS: LOW TO MEDIUM PROB FOR THUNDER AFTER 21-22Z. STORMS SHOULD WEAKEN AS THEY APPROACH THE AIRPORT. KISP FCSTER COMMENTS: STRATUS SHOULD BURN OFF BY 19-20Z. STRATUS AND FOG LIKELY IMPACTS THE AIRPORT AFTER SUNSET. .OUTLOOK FOR 18Z THURSDAY THROUGH MONDAY... .THU AFTERNOON...ISOLATED TO SCT TSTMS POSSIBLE INVOF A WEAKENING COLD FRONT. SW FLOW DIMINISHING AND POSSIBLY BECOMING NW OR VRB. .FRI...VFR WITH LGT NE WINDS VEERING THRU THE DAY. .SAT...MRNG MVFR OR LOWER POSSIBLE. CHC SHWRS AND TSTMS IN THE AFTN AND OVERNIGHT WITH MVFR OR LOWER. STRONG SLY FLOW. .SUN...MVFR OR LOWER IN SHOWERS/TSTMS POSSIBLE. SHIFTING WINDS TO THE E/NE. .MON...POSSIBLE IMPROVEMENT TO VFR IF SHOWERS/TSTMS MOVE TO THE SOUTH. E/NE FLOW. && .MARINE... SEAS SHOULD BUILD TO 5 FT OVER THE OCEAN WATERS THROUGH TONIGHT. DO NOT THINK SEA BREEZE WILL BE STRONG ENOUGH TO BRING GUSTS UP TO 25 KT TO NY HARBOR OR THE SOUTH SHORE BAYS...SO HAVE CANCELLED SCA THERE. GUSTS SHOULD PEAK AT OR JUST OVER 20 KT IN THOSE AREAS. NY HARBOR AND WRN LONG ISLAND SOUND COULD EXPERIENCE EITHER DIRECT TSTM IMPACTS OR A GUST FRONT FROM WEAKENING INLAND STORMS TOWARD EVENING. THERE WILL BE A BRIEF PERIOD OF OFFSHORE WINDS THURSDAY NIGHT BEHIND A DISSIPATING COLD FRONT. THEN...MARGINAL SMALL CRAFT CONDITIONS ON THE OCEAN WATERS WILL BE POSSIBLE FRIDAY THROUGH SUNDAY WITH A MODERATE SOUTHERLY FLOW. && .HYDROLOGY... THERE IS THE POTENTIAL FOR BASIN AVERAGE OF 1/4 TO 1/2 INCH OF RAIN ACROSS THE LOWER HUDSON VALLEY/NE NJ/SW CT THIS AFTERNOON/EVENING. NOTING PRECIP EFFICIENCY OF JUST OVER 1.5 INCH AND CORFIDI VECTORS 10 KT OR LESS...THERE IS THE POTENTIAL FOR TRAINING OF CELLS THAT COULD LEAD TO RAINFALL OF 1-2 INCHES...WITH MINOR FLOODING OF URBAN/POOR DRAINAGE AREAS. ON THURSDAY THERE IS THE POTENTIAL FOR LESS THAN 1/4 OF AN INCH OF BASIN AVERAGE RAINFALL. HOWEVER...WITH STORM MOTION OF AROUND 10 KT AND PRECIP EFFICIENCY NEAR 1.25 INCHES...THERE IS STILL POTENTIAL FOR SLOW MOVING STORMS PRODUCING LOCALLY MODERATE TO HEAVY RAINFALL...ESPECIALLY OVER SOUTHERN CT. THIS COULD RESULT IN THE MINOR FLOODING OF URBAN/POOR DRAINAGE AREAS...ESPECIALLY IF IT OCCURS OVER AREAS RECEIVING LOCALLY HEAVY RAINFALL TODAY. THERE IS THE POTENTIAL FOR AN ORGANIZED RAINFALL EVENT LATE IN THE WEEKEND INTO EARLY NEXT WEEK AS COLD FRONT MOVES INTO THE AREA. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT THURSDAY FOR ANZ350-353- 355. && $$ SYNOPSIS...GOODMAN NEAR TERM...GOODMAN SHORT TERM...GOODMAN LONG TERM...JM AVIATION...PW MARINE...GOODMAN/JM HYDROLOGY...GOODMAN/JM

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