Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 270839 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 439 AM EDT WED MAY 27 2015 .SYNOPSIS... HIGH PRESSURE SLIDES FARTHER OFFSHORE TODAY. A COLD FRONT APPROACHES FROM THE WEST TONIGHT...THEN CROSSES THE AREA ON THURSDAY...SLIDING TO THE SOUTH THURSDAY NIGHT. MEANWHILE...HIGH PRESSURE WILL REMAIN OFF THE ATLANTIC COAST. A STRONGER COLD FRONT WILL THEN IMPACT THE AREA FROM SUNDAY INTO EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... MAIN FOCUS TODAY IS HOW MUCH CONVECTION DEVELOPS IN RESPONSE TO A WEAK 700-500 HPA SHORTWAVE...CURRENTLY STRETCHING FROM UPSTATE SC INTO OH...THAT CROSSES THE AREA THIS AFTERNOON IS AT CONTINUES TO WEAKEN. SHOULD ALSO BE ABLE TO ACHIEVE SOME LIFT OVER THE LOWER HUDSON VALLEY/NE NJ AS THE SEABREEZE INTERSECTS A WEAK THERMAL TROUGH FORECAST TO SET UP THERE THIS AFTERNOON. WITH FORECAST CAPES OVER THE LOWER HUDSON VALLEY/NE NJ/SW CT ON AVERAGE OF 1500-2500 J/KG...25-30KT OF 0-6KM SHEAR AND THE REGION IN THE RIGHT REAR QUADRANT OF A 85KT 300 HPA JET...HAVE THE POTENTIAL FOR SOME ISOLATED TO SCATTERED SEVERE THUNDERSTORMS OVER THIS AREA. BULK RICHARDSON NUMBERS GENERALLY 25-50 DO SUPPORT THE POSSIBILITY OF A DISCRETE SUPERCELL...WITH MAINLY MULTICELLULAR CONVECTION. THE SEVERE THREAT IS GENERALLY CONSISTENT WITH SPC/S AREA OF MARGINAL AND SLIGHT RISK OF THUNDERSTORMS OVER THE AREA. NOT QUITE SO SURE ABOUT THE MARGINAL RISK OVER NYC...AS SEABREEZE COULD STABILIZE THINGS BEFORE ANY CONVECTION ARRIVES THERE. FOR THAT REASON WILL ONLY HIGHLIGHT THE SEVERE THREAT IN THE HWO FOR THE LOWER HUDSON VALLEY/NE NJ AND SW CT AT THIS TIME. HOWEVER CANNOT COMPLETELY RULE OUT A SEVERE THUNDERSTORM MOVING INTO NYC. THE MAIN THREAT WOULD BE FOR STRONG GUSTY WINDS. THERE IS ALSO THE THREAT FOR LOCALLY HEAVY RAINFALL WITH ANY STRONGER CONVECTION...REFER TO THE HYDROLOGY SECTION OF THE AFD FOR DETAILS. FOR NOW APPEARS MOST IF NOT ALL OF LONG ISLAND AND SE CT SHOULD BE TOO STABLE IN THE LOW LEVELS DUE TO MARINE INFLUENCE TO KEEP ANY CONVECTION AT BAY...HOWEVER DUE TO PROXIMITY DUE HAVE SLIGHT CHANCE POPS IN N MIDDLESEX...N NASSAU AND NW SUFFOLK COUNTIES THIS AFTERNOON AS WELL. FOR HIGHS TODAY USED A BLEND OF MAV/MET/ECS GUIDANCE WITH NAM 2-METER TEMPERATURES AND A MIX DOWN FROM 975-850 HPA PER BUFKIT SOUNDINGS. HIGHS SHOULD BE 5-10 DEGREES ABOVE NORMAL. THERE IS A MODERATE RISK FOR THE METEOROLOGICAL ENHANCEMENT OF RIP CURRENT DEVELOPMENT AT ATLANTIC BEACHES INTO THIS EVENING. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... COULD SEE STORMS LINGER INTO THE EVENING ACROSS THE NW 1/2 OF THE CWA...OTHERWISE SHOULD BE DRY TONIGHT ABSENT ANY NOTABLE FORCING. IT WILL BE NOTABLY HUMID...WITH DEWPOINTS MAINLY IN THE LOWER TO MID 60S. LOWS TONIGHT WERE BASED ON A BLEND OF NAM 2-METER TEMPERATURES WITH ECS/MET/MAV GUIDANCE...WITH VALUES AROUND 10-15 DEGREES ABOVE NORMAL. THERE IS SOME POTENTIAL FOR FOG TONIGHT...DEPENDING ON EXACTLY WHERE/HOW MUCH IT RAINS THIS AFTERNOON. NOTING THAT FOG HAS NOT MATERIALIZED THE PAST FEW NIGHTS...DO NOT HAVE THE CONFIDENCE TO CONTINUE WITH PATCHY FOG IN THE FORECAST FOR TONIGHT. 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...AND KEPT SE SUFFOLK COUNTY AT SLIGHT CHANCE. PROBABILITIES ARE HIGHEST OVER THE NW 1/2 OF THE CWA WHERE THE INSTABILITY IS HIGHEST. WITH SLIGHTLY LESS CAPE - 1000-2000 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 OR TWO STRONG TO SEVERE STORM CANNOT BE COMPLETELY RULED OUT. FOR HIGHS THURSDAY USED A BLEND OF MIXING DOWN FROM 975 TO 825 HPA PER BUFKIT SOUNDINGS WITH NAM 2-METER TEMPERATURES AND A MIXTURE OF ECS/MAV/MET GUIDANCE. HIGHS SHOULD BE AROUND 10-15 DEGREES ABOVE NORMAL. IT WOULD NOT BE SURPRISING IF A FEW LOCATIONS IN NE NJ AND/OR NORTHERN PORTIONS OF NYC CAME IN WITH A HIGH AT OR JUST ABOVE 90.DEWPOINTS ON THURSDAY SHOULD BE A TAD LOWER THAN TODAY...MAINLY IN THE UPPER 50S...SO HEAT INDICES SHOULD PEAK OUT IN WARMER AREAS IN THE MID 80S. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... A WEAK COLD FRONT WILL MOVE ACROSS THE AREA THURSDAY NIGHT BEFORE DISSIPATING OFFSHORE ON FRIDAY. LITTLE TO NO PRECIPITATION IS EXPECTED WITH THE FRONT. 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 /09Z WEDNESDAY THROUGH SUNDAY/...
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A WEAK COLD FRONT WILL APPROACH THE REGION TODAY...AND DISSIPATE OVER THE AREA THU. MAINLY VFR THIS MRNG...HOWEVER THERE IS THE POTENTIAL FOR SOME POCKETS OF STRATUS AND BR WHICH COULD BRING MVFR. ANY MVFR BURNS OFF BY 13-15Z EXCEPT KGON WHERE THERE IS THE POTENTIAL THAT IT COULD LINGER MOST IF NOT ALL OF THE DAY. OTHERWISE...AFTN TSTMS LIKELY TO DEVELOP ACROSS THE LOWER HUDSON VALLEY AFT 18Z. THE ACTIVITY MAY HOLD TOGETHER TO IMPACT AREAS ROUGHLY ALONG AND W OF A KHPN-KEWR LINE. MVFR OR LOWER AT TIMES TNGT WITH STRATUS AND POSSIBLY FOG. S TO SW FLOW THRU THE TAF PERIOD. HIGHEST SPEEDS THIS AFTN INTO EARLY EVE...ESPECIALLY INVOF KJFK WHERE SUSTAINED AROUND 20KT EXPECTED. ...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 MVFR CIGS THRU 14Z. KLGA FCSTER COMMENTS: LOW PROB FOR MVFR CIGS THRU 14Z. KEWR FCSTER COMMENTS: LOW PROB FOR MVFR CIGS THRU 14Z. THE AFTERNOON KEWR HAZE POTENTIAL FORECAST IS GREEN...WHICH IMPLIES SLANT RANGE VISIBILITY 7SM OR GREATER OUTSIDE OF CLOUD. KTEB FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. KHPN FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. KISP FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS EXPECTED. .OUTLOOK FOR 06Z THURSDAY THROUGH SUNDAY... .LATE TNGT...MVFR OR LOWER AT TIMES WITH SW FLOW. .THU...MRNG MVFR OR LOWER. 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...POSSIBLE IMPROVEMENT TO VFR. NE WINDS.
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&& .MARINE... SEAS SHOULD REMAIN AT OR ABOVE 5 FT OVER AT LEAST THE SOUTHERN PORTION OF THE COASTAL OCEAN WATERS THROUGH TONIGHT...SO HAVE CONTINUED THE SCA THERE. ONCE AGAIN APPEARS THE SEA BREEZE WILL BE STRONG ENOUGH TO BRING GUSTS TO AROUND 25 KT TO THE COASTAL OCEAN WATERS AND TO NEW YORK HARBOR AND THE SOUTH SHORE BAYS OF LONG ISLAND. HAVE ISSUED A SMALL CRAFT ADVISORY FOR THOSE TWO ZONES FROM NOON UNTIL MIDNIGHT AS WELL. ON THE SOUND AND EASTERN BAYS OF LONG ISLAND...GUSTS SHOULD PEAK OUT AT 20 KT THIS AFTERNOON/EVENING...WITH MAYBE SOME OCCASIONAL GUSTS TO 25 KT. FOR THURSDAY FOR NOW IT APPEARS SEABREEZE SHOULD BE WEAKER...AND THE PRESSURE GRADIENT SLIGHTLY MORE RELAXED...SO EXPECTING SUB-SCA CONDITIONS ON ALL WATERS. HAVE ADJUSTED WAVEWATCH DOWN 1 FT TODAY-THURSDAY...AS IT HAS GENERALLY BEEN OVER FORECASTING WAVE HEIGHTS AT THE BUOYS BY ABOUT THAT AMOUNT. 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 AROUND 1/4 AN INCH OF RAINFALL ACROSS THE LOWER HUDSON VALLEY/NE NJ/SW CT THIS AFTERNOON/EVENING...WITH LESSER AMOUNTS...DOWN TO ZERO ELSEWHERE. NOTING PRECIPITABLE WATERS FORECAST TO BE AROUND 1.75 INCHES AND STORM MOTION FORECAST TO BE AROUND 10 KT...THERE IS THE POTENTIAL FOR SLOW MOVING STORMS THAT PRODUCE LOCALLY HEAVY RAINFALL IN ANY STRONGER CONVECTION. THIS COULD LEAD TO 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 PRECIPITABLE WATERS AROUND 1.25 INCHES...THERE IS THE POTENTIAL FOR SLOW MOVING STORMS PRODUCING LOCALLY MODERATE TO HEAVY RAINFALL. 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. SMALL CRAFT ADVISORY FROM NOON TODAY TO MIDNIGHT EDT TONIGHT FOR ANZ338-345. && $$ SYNOPSIS...BC/MALOIT NEAR TERM...MALOIT SHORT TERM...MALOIT LONG TERM...BC AVIATION...JMC MARINE...BC/MALOIT HYDROLOGY...BC/MALOIT

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