Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 272003 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 403 PM EDT WED MAY 27 2015 .SYNOPSIS...
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A COLD FRONT WILL APPROACH FROM THE WEST TONIGHT...THEN MOVE ACROSS THURSDAY INTO THURSDAY NIGHT. HIGH PRESSURE WILL RETURN ON FRIDAY...QUICKLY MOVING INTO THE WESTERN ATLANTIC LATE FRIDAY AFTERNOON INTO THE WEEKEND. A SLOW MOVING COLD FRONT APPROACHING FROM THE WEST WILL EVENTUALLY MOVE IN SATURDAY NIGHT AND STALL NEARBY FOR SUNDAY INTO EARLY NEXT WEEK. HIGH PRESSURE WILL BUILD IN FROM THE NORTH LATE TUESDAY INTO THE MIDDLE OF NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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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. HRRR ALSO INDICATES POTENTIAL FOR ISOLD DISCRETE CELLS OUT AHEAD OF THE LINE. STRONGER CELLS/BOWING LINE SEGMENTS WITH THE LINE 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 BE 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.
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&& .SHORT TERM /6 AM THURSDAY MORNING 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 WEDNESDAY/...
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RIDGING TREND RESUMES ALOFT WITH JET STREAM WELL NORTH OF THE REGION FOR FRIDAY. THIS RIDGE SHIFTS SLOWLY OFFSHORE AND BECOMES LESS AMPLIFIED AS A LONGWAVE TROUGH PUSHES EASTWARD ACROSS SOUTHERN CANADA. THE SAME PATTERN REMAINS THROUGH THE FIRST HALF OF THE WEEKEND AND THEN THE JET PUSHES FARTHER SOUTH INTO THE REGION FOR THE REST OF THE WEEKEND INTO EARLY NEXT WEEK. THE MID LEVEL RIDGE WILL BECOME MORE BROAD SUNDAY WITH A SHORTWAVE MOVING IN EARLY NEXT WEEK. THE RIDGING RESUMES BY MID NEXT WEEK WITH JET STREAM ONCE AGAIN MOVING WELL NORTH OF THE REGION. AT THE SURFACE...HIGH PRESSURE FROM THE CANADIAN MARITIMES QUICKLY SETTLES INTO THE WESTERN ATLANTIC LATE AFTERNOON FRIDAY AND INTO THE WEEKEND. THE INFLUENCE OF THE HIGH WILL LESSEN WITH TIME AS A SLOW MOVING COLD FRONT APPROACHES FROM THE WEST. THE PARENT LOW ATTACHED TO THIS FRONT WILL NOT BE THAT STRONG...SLOWLY DEEPENING WITH EASTWARD PROGRESS THROUGH SATURDAY AND THEN DEEPENS MORE WITHIN THE CANADIAN MARITIMES SUNDAY THROUGH SUNDAY NIGHT. THE COLD FRONT WILL BE MOVING WITHIN CLOSER PROXIMITY OF THE REGION THROUGH THIS TIME. THE FRONT WILL THEN STALL NEAR THE REGION WITH LOW PRESSURE AND INVERTED TROUGH DEVELOPING AT THE SURFACE TO THE SOUTHWEST OF THE REGION ALONG THE FRONT. HIGH PRESSURE RETURNS LATE TUESDAY FROM THE CANADIAN MARITIMES...BUT ONCE AGAIN BECOMES RE-ESTABLISHED QUICKLY OFFSHORE INTO THE WESTERN ATLANTIC. IN TERMS OF WEATHER...CONDITIONS REMAIN DRY FRIDAY AND FRIDAY NIGHT. HOWEVER...WITH THE MOIST SOUTHERLY FLOW FRIDAY NIGHT INTO SATURDAY MORNING...EXPECTING SOME PATCHY FOG ACROSS THE REGION...ESPECIALLY COASTAL REGIONS. SOME MODELS ARE SHOWING THIS MOISTURE AS VERY LIGHT QPF. THERE WILL BE A GRADUAL INCREASING CHANCE OF SHOWERS AND THUNDERSTORMS FIRST NORTH AND WEST OF NYC SATURDAY AHEAD OF THE COLD FRONT. THE CHANCES FOR SHOWERS AND THUNDERSTORMS INCREASE SATURDAY NIGHT ACROSS THE WHOLE FORECAST REGION WITH SHOWERS BECOMING LIKELY SUNDAY AND SUNDAY NIGHT. THUNDERSTORMS WILL BE MORE LIMITED SUNDAY AND SUNDAY NIGHT WITH DECREASING INSTABILITY WITH A MORE NORTHERLY AND EASTERLY FLOW DEVELOPING DURING THE DAY. WITH THE FRONT STALLING NEAR THE REGION...CHANCES FOR SHOWERS REMAIN INTO EARLY NEXT WEEK...BEFORE BECOMING MORE MINIMAL TUESDAY AS THE FRONT PUSHES FARTHER SOUTH OF THE AREA WITH MAINLY DRY CONDITIONS RETURNING LATE TUESDAY NIGHT INTO NEXT WEDNESDAY. THE AIR MASS WILL STAY MOSTLY AS MARITIME TROPICAL THROUGH THE LONG TERM BUT A LITTLE COOLER FOR MONDAY AND TUESDAY NEXT WEEK. THE HIGHS ARE FORECAST TO BE AROUND OR SLIGHTLY MORE THAN 5 DEGREES ABOVE NORMAL ON AVERAGE FRIDAY AND SATURDAY...NEAR NORMAL FOR SUNDAY...AROUND 5 DEGREES BELOW NORMAL MONDAY AS WELL AS A FEW DEGREES BELOW NORMAL TUESDAY. TEMPERATURE RETURN TO NEAR NORMAL BY MID NEXT WEEK. LOWS AT NIGHT OVERALL ARE FORECAST TO BE NEAR TO ABOVE NORMAL.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
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A WEAK COLD FRONT WILL APPROACH THE REGION TONIGHT AND PASS ACROSS ON THURSDAY. MAINLY VFR THROUGH THE EVENING OUTSIDE OF AN THUNDERSTORMS. STRATUS TO THE EAST SHOULD TEMPORARILY SCOUR OUT. AS FOR THUNDERSTORMS...BEST CHANCE FOR THUNDER LATE THIS AFTERNOON/EARLY EVENING WILL BE AT KEWR/KTEB AND KSWF. ANY STORMS WOULD WEAKEN AS THEY MOVE EAST OF THE HUDSON RIVER. 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. GENERALLY EXPECT ANY THUNDERSTORMS TO WEAKEN AS THEY TRACK TOWARD THE AIRPORT. KLGA FCSTER COMMENTS: LOW PROB FOR THUNDER. GENERALLY EXPECT ANY THUNDERSTORMS TO WEAKEN AS THEY TRACK TOWARD THE AIRPORT. KEWR FCSTER COMMENTS: SE WINDS ARE EXPECTED TO VEER BACK TO THE SOUTH/SOUTHWEST BEFORE 00Z. MEDIUM PROB FOR THUNDER. STORMS SHOULD WEAKEN AS THEY APPROACH THE AIRPORT. KTEB FCSTER COMMENTS: MEDIUM PROB FOR THUNDER. STORMS SHOULD WEAKEN AS THEY APPROACH THE AIRPORT. KHPN FCSTER COMMENTS: LOW TO MEDIUM PROB FOR THUNDER. STORMS SHOULD WEAKEN AS THEY APPROACH THE AIRPORT. KISP FCSTER COMMENTS: LINGERING STRATUS SHOULD BURN OFF OR MOVE EAST LATE THIS AFTERNOON BRIEFLY BEFORE DEVELOPING OR MOVING BACK IN 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.
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&& .MARINE...
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SEAS SHOULD BUILD TO 5 FT OVER THE OCEAN WATERS BY TONIGHT...WITH GUSTS UP TO 25 KT EAST OF SANDY HOOK WITH USUAL LATE DAY/EVENING SOUTHERLY SEA BREEZE ENHANCEMENT. NY HARBOR AND WRN LONG ISLAND SOUND COULD EXPERIENCE EITHER DIRECT TSTM IMPACTS OR A GUST FRONT FROM WEAKENING INLAND STORMS TOWARD EVENING. PERSISTENT SOUTHERLY FETCH COULD BUILD SEAS ON THE OCEAN TO 5 FT SATURDAY...AND REMAIN THERE FOR THE REST OF THE FCST PERIOD...EVEN AS WINDS SWITCH TO MORE EASTERLY SUNDAY INTO EARLY NEXT WEEK.
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&& .HYDROLOGY...
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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 POTENTIAL FOR HEAVY RAIN SUNDAY AND SUNDAY NIGHT WITH PW FORECAST TO REACH UP TO NEAR 1.75 INCHES. THERE WILL BE POTENTIAL AS WELL FOR AN EXTENDED WIDESPREAD RAINFALL LATE THIS WEEKEND INTO EARLY NEXT WEEK WITH A COLD FRONT STALLING NEARBY.
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&& .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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