Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 210622 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 222 AM EDT TUE OCT 21 2014 .SYNOPSIS... LOW PRESSURE MOVES IN FROM THE WEST TONIGHT AND REMAINS IN THE VICINITY THROUGH THE MID TO LATE WEEK PERIOD BEFORE MOVING INTO THE CANADIAN MARITIME PROVINCES BY SATURDAY MORNING. A COLD FRONT APPROACHES FROM THE NORTHWEST SATURDAY...THEN CROSSES THE TRI- STATE SATURDAY NIGHT. HIGH PRESSURE THEN BUILDS INTO THE MID ATLANTIC STATES EARLY NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... MINOR UPDATE TO ADJUST THE DIURNAL CURVE. CLOUD COVER HAS SLOWED THE COOLING IN OUTLYING AREAS. NO OTHER MAJOR CHANGES MADE. UPPER TROUGH SHIFTS TOWARDS US TONIGHT ALONG WITH A BROAD AREA OF LOW PRESSURE AT THE SURFACE. CLOUDS WILL CONTINUE TO LOWER THROUGH THE NIGHT. MODELS AGREE THAT THERE WILL BE SOME ISENTROPIC LIFT AND MOISTURE INCREASING OVER THE EASTERNMOST PORTION OF THE TRI STATE AREA LATE AT NIGHT BUT WITH SOME DIFFERENCES IN PLACEMENT. THERE WILL ALSO BE INCREASING PVA...ESPECIALLY WEST OF THE HUDSON AS THE UPPER TROUGH AXIS APPROACHES. WILL CONTINUE WITH OVERALL SLIGHT CHANCE TO CHANCE POPS FOCUSED MAINLY AFTER MIDNIGHT TONIGHT...BUT WILL GO WITH THE HIGHEST CHANCES FOR THE FAR EASTERN AND FAR WESTERN AREAS. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... THE SYSTEM SHIFTS EAST DURING TUESDAY...WITH A SURFACE LOW CENTER STARTING TO DEVELOP NEAR THE NORTHERN MID-ATLANTIC COAST BY THE END OF THE DAY. OVERALL LIFT IS NOT IMPRESSIVE...HOWEVER WITH CONTINUED PVA AND STEEPENING LAPSE RATES IN THE MID LEVELS...THINKING IS THAT THERE WILL BE AT LEAST SCATTERED SHOWERS AROUND. FOR THE AFTERNOON...THERE WILL ALSO BE A SLIGHT CHANCE OF A THUNDERSTORM WITH BETTER THE STEEPER LAPSE RATES AND ELEVATED CAPE. THE HIGH TEMPERATURE FORECAST IS TRICKY FOR TUESDAY AS EXTENDED BREAKS OF PARTLY TO MOSTLY SUNNY CONDITIONS COULD DEVELOP. HAVE GONE WITH A MAV/NAM MOS BLEND FOR HIGHS...WHICH WERE SIMILAR. THE LOW STRENGTHENS TO OUR SOUTH TUESDAY NIGHT...WITH OVERALL BETTER LIFT FAVORING THE SOUTHWEST HALF OF THE TRI STATE AREA. HAVE GONE WITH LIKELY POPS LATE AT NIGHT HERE...WITH CHC POPS ELSEWHERE. ELEVATED CAPE REMAINS WITH ISO TSTMS...GENERALLY SHIFTING EAST AS THE NIGHT PROGRESSES. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... CONFIDENCE IS HIGH THAT A CUTOFF LOW WILL TRACK FROM NEAR THE MID ATLANTIC COAST WEDNESDAY MORNING TO SOMEWHERE NEAR NOVA SCOTIA BY SATURDAY MORNING. AS A RESULT HAVE GONE WITH A MODEL BLEND THROUGH THEN. IT ALSO APPEARS THERE WILL BE SUFFICIENT MID LEVEL INSTABILITY OVER THE ENTIRE CWA...AND TO SOME EXTENT LOW LEVEL INSTABILITY MAINLY OVER SOUTHERN AND FAR EASTERN ZONES...TO WARRANT A SLIGHT CHANCE OF THUNDER WEDNESDAY AND WEDNESDAY NIGHT...IN ADDITION TO LIKELY POPS FOR RAIN. APPEARS ALL INGREDIENTS COME TOGETHER ISENTROPICALLY TO WARRANT FORECASTING MODERATE RAINFALL FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY NIGHT...WITH THE MODERATE RAINFALL POTENTIAL RETREATING TO THE NORTHEAST DURING THE DAY ON THURSDAY. AS THE CUTOFF LOW PULLS AWAY THERE WILL BE A CHANCE OF SHOWERS THURSDAY NIGHT...TAPERING OFF TO A SLIGHT CHANCE OF SHOWERS BY FRIDAY AFTERNOON. FOR NOW IT APPEARS FRIDAY NIGHT SHOULD BE DRY DUE TO SUBSIDING NW BOUNDARY LAYER FLOW. REFER TO THE HYDROLOGY SECTION OF THE AFD FOR STORM TOTAL QPF AND ANY POTENTIAL IMPACTS. THE GFS AND ECMWF AGREE ON THE GENERAL FEATURES TO IMPACT THE AREA SATURDAY THROUGH MONDAY...BUT DIFFER ON TIMING...AND SOUTHERN PUSH OF A SURFACE COLD FRONT SATURDAY NIGHT. NOTING THE GFS SEEMS TO BE LIVING UP TO ITS PROGRESSIVE BIAS...AND THE CONSISTENCY OF THE ECMWF AND NOTING THAT THE CMC SUPPORTS THE ECMWF...LEANED TOWARDS THE ECMWF IN THIS TIME FRAME. SATURDAY SHOULD BE DRY WITH A SHORTWAVE RIDGE CROSSING THE AREA. 700-500 HPA TROUGH THEN CROSSES THE AREA SATURDAY NIGHT AND SUNDAY...BUT WITH LIMITED LOW LEVEL MOISTURE TO WORK WITH...IT SHOULD PASS BY DRY. A DEEP LAYERED RIDGE THEN BUILDS IN THEN BEGINS TO BUILD INTO THE REGION INTO MONDAY. FOR TEMPERATURES IN THE LONG TERM: A BLEND OF MAV/MET/ECS GUIDANCE...WITH NAM 2-METER TEMPERATURES AND A MIX DOWN FROM 975-950 HPA PER BUFKIT SOUNDINGS WAS USED FOR HIGHS ON WEDNESDAY...WITH VALUES FORECAST TO BE AROUND 5 DEGREES BELOW NORMAL. FOR LOWS WEDNESDAY NIGHT A BLEND OF MAV/MET GUIDANCE WITH NAM 2-METER TEMPERATURES WAS USED - WITH READINGS FORECAST TO BE NEAR NORMAL IN NYC AND AROUND 5 DEGREES ABOVE NORMAL ELSEWHERE. FOR HIGHS ON THURSDAY A BLEND OF MEX/MEN/EKD/ECE/ECM/WPC GUIDANCE WAS USED WITH NAM 2-METER TEMPERATURES AND A MIX DOWN FROM 950-925 HPA PER BUFKIT SOUNDINGS - WITH VALUES EXPECTED TO BE AROUND 5 DEGREES BELOW NORMAL. FROM THURSDAY NIGHT-MONDAY A BLEND OF MEX/MEN/EKD/ECE/ECM/WPC GUIDANCE WAS USED...WITH ECMWF 2-METER TEMPERATURES BLENDED IN SUNDAY AND SUNDAY NIGHT...AND THE BLEND ADJUSTED UPWARD 1-2 CATEGORIES TO COUNTER BIAS TOWARDS CLIMATOLOGY IN THE GUIDANCE THAT FAR OUT IN TIME - NOTING FORECAST 850 TEMPERATURES OF AT LEAST 10C IN ALL MODELS ON MONDAY. LOWS ARE FORECAST TO RUN ABOVE NORMAL THURSDAY NIGHT-SUNDAY NIGHT...WHILE HIGHS ARE FORECAST TO BE ABOVE NORMAL...EXCEPT SLIGHTLY BELOW NORMAL ON SUNDAY. HIGHS ON MONDAY COULD VERY WELL END UP 5+ DEGREES WARMER THAN FORECAST IF CURRENT TRENDS HOLD. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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LOW PRESSURE APPROACHES FROM THE NORTHWEST THROUGH TONIGHT...THEN BECOMES NEARLY STATIONARY ACROSS NEW YORK...PENNSYLVANIA...AND INTO VIRGINIA TUESDAY AS ANOTHER LOW DEVELOPS OFF THE COAST. TRICKY FORECAST NEXT 24 HOURS WITH A WEAK PRES GRADIENT FOR MOST OF THE PERIOD LEADING TO LIGHT AND VRB WINDS. TRIED TO PINPOINT A DIRECTION...BUT DIRECTIONS COULD BE ALL OVER THE PLACE UNTIL THE LOW TRACKS TO THE S OF THE AREA AND A NE FLOW BETWEEN 5 AND 10 KT DEVELOPS THIS EVE. CONDS SHOULD BE VFR FOR THE MAJORITY OF THE PERIOD...BUT COULD SEE ISOLD MVFR IN ANY RAIN THAT MOVES DIRECTLY OVER ANY OF THE TERMINALS. SPEAKING OF RAIN...TOUGH TO PINPOINT WHEN AND WHERE BUT DO NOT EXPECT A PROLONGED PERIOD OF PCPN AT ANY OF THE TERMINALS...EXCEPT KSWF. AM PROBABLY TOO EARLY IN STEADY -RADZ BEGINNING AT 23Z TONIGHT...BUT FURTHER ADJUSTMENTS CAN BE MADE IN SUBSEQUENT TAFS. .OUTLOOK FOR 06Z WEDNESDAY THROUGH SATURDAY... .TUE NIGHT...MVFR TO LOCALLY IFR CONDS DEVELOPING WITH SCT LIGHT RAIN. .WED THROUGH THU...MVFR OR LOWER CONDS IN RAIN. NLY FLOW 10 TO 15 KT G20-25KT. .FRI...IMPROVING CONDS. NW WINDS 15-20 KT WITH 20-25 KT GUSTS. .SAT..VFR. NW G20KT.
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&& .MARINE... SW WINDS EXPECTED TO SUBSIDE TONIGHT WITH A SOMEWHAT WEAKER PRESSURE GRADIENT DEVELOPING OVER THE WATERS. WINDS GRADUALLY BACK TOWARDS THE EAST BY LATE IN THE DAY TUESDAY...THEN AS A LOW CENTER DEVELOPS TO THE SOUTH TUESDAY NIGHT...WINDS BACK FARTHER TOWARDS THE NE AND PICK UP AS THE LOW BECOMES STRONGER. WINDS AND SEAS SHOULD HOWEVER REMAIN BELOW ADVISORY LEVELS THROUGH THIS PERIOD. DUE TO UNCERTAINTY IN THE EXACT TRACK AND STRENGTH OF A COASTAL LOW WEDNESDAY THROUGH FRIDAY...THERE IS A DEGREE OF UNCERTAINTY IN THE FORECAST IN THAT TIME FRAME THAT IS GREATER THAN NORMAL. FOR NOW IT APPEARS THERE IS A HIGH CHANCE OF SMALL CRAFT ADVISORY CONDITIONS ON THE COASTAL OCEAN WATERS FROM WEDNESDAY THROUGH THURSDAY NIGHT...WITH A CHANCE OF SMALL CRAFT CONDITIONS ON THE REMAINDER OF THE WATERS DURING THIS TIME FRAME. SUB-SMALL CRAFT CONDITIONS ARE FORECAST ON ALL WATERS FRIDAY-SATURDAY - HOWEVER THERE IS A SMALL CHANCE THAT SMALL CRAFT CONDITIONS COULD LINGER INTO FRIDAY ON THE EASTERN WATERS. && .HYDROLOGY... DRY TODAY...WITH SPOTTY LIGHT RAINFALL AMOUNTS POSSIBLE TONIGHT. THERE IS THE POTENTIAL FOR AROUND AN INCH OF RAIN FROM TUESDAY NIGHT INTO THURSDAY NIGHT OVER THE WESTERN 1/3 OF THE CWA...INCLUDING NYC...AND UP TO 1 1/3 INCHES OF RAIN OVER THE EASTERN 2/3 OF THE CWA...WITH THE BEST POTENTIAL FOR THE HIGHEST AMOUNTS OVER EASTERN CT AND LONG ISLAND. THERE IS THE POTENTIAL FOR LOCALLY HIGHER AMOUNTS IN ANY AREA EXPERIENCING STRONGER CONVECTION...WHICH IS LOCALLY POSSIBLE TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. IF THIS OCCURS...THEN THERE IS THE POTENTIAL FOR LOCALIZED MINOR URBAN/POOR DRAINAGE FLOODING. OTHERWISE...WITH THE PRECIPITATION FALLING OVER 48+ HOURS...LITTLE OR NO SIGNIFICANT HYDROLOGIC IMPACT IS EXPECTED. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...NONE. && $$

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