Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 051220 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 720 AM EST THU MAR 5 2015 .SYNOPSIS... AN ARCTIC FRONT WILL SLIDE TO THE SOUTHEAST THIS MORNING. MEANWHILE...A SERIES OF WEAK WAVES OF LOW PRESSURE WILL TRACK ALONG A STATIONARY FRONT TO THE SOUTH OF THE REGION. CANADIAN HIGH PRESSURE BUILDS IN TONIGHT THROUGH FRIDAY...THEN BUILDS TO THE SOUTH THROUGH EARLY NEXT WEEK AS SEVERAL WEAK IMPULSES PASS TO THE NORTH. THE HIGH SLIDES OFFSHORE MONDAY NIGHT AND TUESDAY. A COLD FRONT PASSES THROUGH ON WEDNESDAY...FOLLOWED BY CANADIAN HIGH PRESSURE FOR THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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FORECAST ON TRACK THIS MORNING...WITH SNOW OF MODERATE TO HEAVY INTENSITY DEVELOPING ACROSS NYC/NJ METRO AND LI...WITH SNOWFALL RATES OF UP TO 1 INCH PER HOUR. LIGHT TO MODERATE SNOW TO THE NORTH. DIFFICULT TRAVEL CONDITIONS EXPECTED THROUGH THE TAIL END OF THE MORNING COMMUTE AND INTO THIS AFTERNOON WITH SNOW COVERED ROADS AND TEMPERATURES DROPPING BELOW FREEZING AND CAUSING ICING OF UNTREATED SURFACES. OTHERWISE...MODELS IN GOOD AGREEMENT WITH DEEP TROUGH AXIS OVER THE CENTRAL US GRADUALLY SLIDING TO EAST COAST BY THIS EVENING...AND THEN OFFSHORE TONIGHT. AHEAD OF IT MOIST SUBTROPICAL PAC MOISTURE PLUME RIDING INTO THE REGION IS EVIDENT IN WV IMAGERY. AT THE SURFACE...A SERIES OF LOW PRESSURE WAVES WILL TRACK NE ALONG A STATIONARY FRONT TO THE SOUTH TODAY...TAPPING INTO THIS MOISTURE...AHEAD OF APPROACHING UPPER TROUGH AXIS AND UNDER INCREASINGLY FAVORABLE ENTRANCE REGION OF A 200KT UPPER JET. BIGGEST MODEL DIFFERENCES COMPARED TO 12 TO 24 HOURS AGO WAS SLOWER COLUMN COOLING EARLY THIS MORNING BY ABOUT 3-4 HOURS...BUT A SLIGHTLY FARTHER NORTH TRACK OF MOISTURE PLUME THROUGH THE DAY TODAY MEANING HIGHER QPF. OVERALL THIS IS LENDING TO A FAIRLY SIMILAR FORECAST OF SNOW AMOUNTS. ARCTIC COLD FRONTAL PASSAGE EXPECTED FROM NW TO SE BETWEEN 10Z TO 15Z...WITH TEMPS IN THE LOWER TO MID 30S...FALLING INTO THE UPPER 20S LATE THIS MORNING...AND DOWN INTO THE LOWER TO MID 20S THIS AFTERNOON. ROAD CONDITIONS EXPECTED TO DETERIORATE IN ITS WAKE...AND COINCIDING AT LEAST PART OF MORNING COMMUTE. ICY CONDITIONS AND SNOW COVERED ROADS EXPECTED FOR AFT/EVE COMMUTE AS WELL. POTENTIAL FOR SNOW TO BE HEAVY AT TIMES THIS MORNING INTO EARLY AFTERNOON ALONG THE COASTAL PLAIN...WITH MODEST FRONTOGENETIC FORCING COUPLED WITH STRONG JET DYNAMICS. SREF IS INDICATING LIKELY PROB OF 1" PER HOUR SNOWFALL RATES DURING THIS TIME FOR NYC/NJ METRO AND LI. SBU WRF SHOWING POTENTIAL FOR 1/2 INCH QPF BETWEEN 7 AM AND 1 PM ACROSS SOUTHERN PORTIONS OF LI/NYC. SNOW SHOULD GRADUALLY TAPER OFF IN INTENSITY AND COVERAGE FROM NW TO SE THIS AFTERNOON AS SHORTWAVE TROUGH APPROACHES AND OFFSHORE STATIONARY FRONT SLIDES WELL OFFSHORE. REGION IS ON EDGE OF A TIGHT PRECIP GRADIENT. HAVE RELIED ON A OPER/HIGH RES ENSEMBLE APPROACH TO QPF...WITH GENERALLY A 1/10TH OR LESS QPF ORANGE COUNTY TO CLOSE TO 7/10 INCH OF QPF ACROSS SOUTHEASTERN LI. THE HIGHEST PROB FOR 1/2 INCH LIQUID QPF REMAINS ALONG SOUTHERN PORTIONS OF THE NYC/NJ METRO AND LI. SNOW TO LIQUID RATIOS WILL INCREASE THROUGH THE MORNING INTO AFTERNOON...WITH HEAVY WET SNOW EARLY THIS MORNING BECOME LIGHT AND POWDERY BY THIS AFTERNOON. IN TERMS OF SNOWFALL TOTALS...A GENERAL 4 TO 7 INCHES OF SNOW STILL EXPECTED FOR NYC/NJ METRO AND LI...WITH HIGHEST AMOUNTS ACROSS SOUTHERN PORTIONS. WARNING CONTINUES HERE. POTENTIAL FOR 2 TO 5 INCHES FOR COASTAL CT AND SOUTHEASTERN CT...THE REST OF NE NJ...AND SOUTHERN PORTIONS OF LOWER HUDSON VALLEY. HIGHEST AMOUNTS ACROSS SOUTHERN SECTIONS. ADVISORY CONTINUES FOR THIS AREA...AND HAVE EXPANDED ADVISORY INTO NORTHERN MIDDLESEX AND NORTHERN NEW LONDON BASED ON TRAJECTORY OF MOISTURE PLUME AND REPORTS OF UP TO 1/2 INCH THERE ALREADY. FINALLY...WITH A SHARP GRADIENT IN PRECIP ACROSS AREAS FAR N&W OF NYC...BETWEEN DUSTING TO 3 INCHES EXPECTED FROM NW TO SE...BUT NOT ENOUGH CONFIDENCE FOR AN ADVISORY AT THIS TIME. ANY LINGERING SNOW ACROSS SOUTHEASTERN LI COMES TO AND END THIS EVENING...WITH FRIGID AND BUT DRYING CONDITIONS TONIGHT. TEMPS EXPECTED TO DROP INTO THE SINGLE DIGITS...LOWER TEENS NYC METRO...ON GUSTY NW WINDS. WINDCHILLS LIKELY DROPPING TO AROUND ZERO FOR MUCH OF THE REGION BY FRIDAY MORNING.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... HIGH PRESSURE BUILDS IN FROM THE WEST THURSDAY NIGHT. SKIES WILL CLEAR FROM WEST TO EAST. WINDS SHOULD DIMINISH LATE AND WITH DRY CONDITIONS...EXPECTING AN UNSEASONABLY COLD NIGHT WITH TEMPERATURES FALLING INTO THE SINGLE DIGITS FOR MOST LOCATIONS AND LOWER TO MIDDLE TEENS IN THE NYC METRO. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... A MEAN TROUGH WILL REMAIN EAST OF THE ROCKIES THROUGH EARLY NEXT WEEK. A SPLIT FLOW THEN DEVELOPS ACROSS THE CONUS WITH A FAST ACTIVE NORTHERN STREAM ACROSS SOUTHERN CANADA AND A BROAD TROUGH IN THE SOUTHERN STREAM EXTENDING FROM THE CENTRAL US THROUGH MEXICO. ZONAL H5 FLOW DEVELOPS ACROSS THE NORTHEAST AS A RESULT. OVERALL...EXPECT MOSTLY DRY CONDITIONS WITH HIGHS WARMING INTO THE 40S BY THE MIDDLE OF NEXT WEEK. A DECENT SHORTWAVE MOVES THROUGH THE NORTHEAST FRI NIGHT...BUT STRONG SUBSIDENCE WITH LIMITED MOISTURE IS EXPECTED TO KEEP THE LOCAL AREA DRY. A TROUGH OF LOW PRESSURE APPROACHES THE AREA SAT AND MOVES THROUGH SAT NIGHT. DOWNSLOPING FLOW ALOFT WILL LIKELY KEEP PCPN CONFINED TO THE WINDWARD SIDE OF THE APPALACHIANS WITH ONLY PERHAPS FLURRIES OR A FEW SNOW SHOWERS AT BEST LATE SAT NIGHT. THE NAM/GFS ARE INDICATING A WEAK LOW PRES SYSTEM MOVING FROM THE GREAT LAKES THROUGH THE NEW ENGLAND ON SUNDAY. EC IS MUCH WEAKER WITH NO PCPN. HAVE MAINTAINED DRY FORECAST AS PCPN REMAINS CONFINED MAINLY TO THE N WHERE BETTER DYNAMICS ARE PRESENT. FINAL NORTHERN STREAM SHORTWAVE PASSES THROUGH MON. GFS IS SLIGHTLY MORE AMPLIFIED ALOFT WITH THE VORT MAX PASSING DIRECTLY OVER THE AREA...ALTHOUGH NOT MUCH PCPN DUE TO RIDGING NOSING IN FROM THE S. EC IS FURTHER N. HAVE MAINTAINED SCHC POPS. SW-W FLOW ALOFT THEN DEVELOPS AT H5...ALTHOUGH LARGE DIFFERENCES BECOME PREVALENT BY THE MIDDLE OF THE WEEK. THE GFS BECOMES MUCH MORE AMPLIFIED WED/THU WITH SOUTHERN STREAM ENERGY BECOMING PICKED UP IN THE FLOW AND PASSING NEAR THE AREA WED. EC IS MUCH FLATTER WITH DRY WEATHER PREVAILING. REMAINING DRY WEATHER THEN PREVAILS POSSIBLY UNTIL MID WEEK. TEMPS WILL START OFF BELOW NORMAL WITH LOWS IN THE TEENS FRI NIGHT AND LOWER 30S SAT...BUT A MODERATION WILL THEN COMMENCE EARLY NEXT WEEK AS HEIGHTS ALOFT GRADUALLY RISE...WITH TEMPS NEAR NORMAL IN THE MID TO UPPER 40S FOR HIGHS AND LOWER 30S FOR LOWS NEXT WEEK. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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WAVES OF LOW PRESSURE RIDE ALONG THE COLD FRONT SOUTHEAST OF LONG ISLAND. PERIODS OF SNOW THROUGH THE DAY...MODERATE TO HEAVY NEAR THE COAST THROUGH THE EARLY AFTERNOON. IFR AND BELOW THROUGH THE DAY FOR MOST TERMINALS EXCEPT FOR KSWF WHICH WILL BE NORTH OF MUCH OF THE SNOW...SO MVFR TO IFR THERE. SNOW TAPERS OFF LATE THIS AFTERNOON INTO EARLY EVENING WHEN CONDITIONS ARE EXPECTED TO SIGNIFICANTLY IMPROVE. WINDS WILL BE OUT OF THE NW AROUND 10-12 KT THROUGH TONIGHT WITH SOME GUSTS TO 15-20 KT TODAY. WINDS DIMINISH LATE TONIGHT INTO FRIDAY. OVERALL...HIGHER CONFIDENCE WITH WINDS AND LOWER CONFIDENCE WITH CATEGORICAL CHANGES WHICH COULD VARY A FEW HOURS WITH SUBSEQUENT FORECASTS. EXPECTED RUNWAY SNOW ACCUMULATIONS: KISP...6-8 INCHES. KJFK/KLGA/KEWR/KTEB/KGON...4-6 INCHES. KHPN/KBDR...3-5 INCHES. KSWF...1-2 INCHES. ...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: FORECAST TIMING OF CATEGORY CHANGES COULD DIFFER 1-3 HRS FROM OBSERVED. KLGA FCSTER COMMENTS: FORECAST TIMING OF CATEGORY CHANGES COULD DIFFER 1-3 HRS FROM OBSERVED. KEWR FCSTER COMMENTS: FORECAST TIMING OF CATEGORY CHANGES COULD DIFFER 1-3 HRS FROM OBSERVED. THE AFTERNOON KEWR HAZE POTENTIAL FORECAST IS GREEN...WHICH IMPLIES SLANT RANGE VISIBILITY 7SM OR GREATER OUTSIDE OF CLOUD. KTEB FCSTER COMMENTS: FORECAST TIMING OF CATEGORY CHANGES COULD DIFFER 1-3 HRS FROM OBSERVED. KHPN FCSTER COMMENTS: FORECAST TIMING OF CATEGORY CHANGES COULD DIFFER 1-3 HRS FROM OBSERVED. KISP FCSTER COMMENTS: FORECAST TIMING OF CATEGORY CHANGES COULD DIFFER 1-3 HRS FROM OBSERVED. .OUTLOOK FOR 12Z FRIDAY THROUGH MONDAY... .FRI-MON...MAINLY VFR.
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&& .MARINE... SMALL CRAFT ADVISORY CONDITIONS CONTINUE ON THE COASTAL OCEAN WATERS INTO FRIDAY MORNING AS A SERIES OF LOW PRESSURE WAVES TRACKS TO THE SOUTH OF THE WATERS AND HIGH PRESSURE BUILDS IN FROM THE WEST. MARGINAL SCA GUSTS TODAY...WITH STRONGEST WINDS TONIGHT. SEAS WILL RUN 4 TO 6 FT THROUGH THE PERIOD...WITH SOUTHERLY SWELLS PREDOMINANT TODAY. LIGHT FREEZING SPRAY EXPECTED TO DEVELOP THIS AFTERNOON ACROSS THE OCEAN WATERS...POSSIBLY BECOMING MODERATE LATE TONIGHT. A PERIOD OF FREEZING SPRAY POSSIBLE ON LI SOUND AS WELL LATE TONIGHT. SUB SCA CONDS RETURN FRI AS HIGH PRESSURE BUILDS OVER THE WATERS. SCA CONDS ARE POSSIBLE...MAINLY ON THE OCEAN WATERS SAT IN THE WAKE OF A TROUGH OF LOW PRES. OTHERWISE...SUB-ADVSY CONDS ARE EXPECTED THROUGH THE PERIOD. && .HYDROLOGY... 1/10 TO 7/10 INCH LIQUID EQUIVALENT PRECIPITATION TODAY. THIS WILL BE FROZEN...SO HYDROLOGIC IMPACTS ARE NOT EXPECTED. NO SIGNIFICANT PCPN IS EXPECTED THROUGH EARLY NEXT WEEK. HOWEVER...TEMPS FORECAST TO WARM INTO THE 40S MAY RESULT IN THE START OF ICE BREAK UP ON AREA RIVERS AND STREAMS. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR CTZ007>012. NY...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR NYZ072>075-078>081-176>179. WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR NYZ069>071. NJ...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR NJZ006- 106>108. WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR NJZ002- 004-103>105. MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EST FRIDAY FOR ANZ350-353-355. && $$ SYNOPSIS...24/NV NEAR TERM...NV SHORT TERM...NV LONG TERM...24 AVIATION...JM MARINE...24/NV HYDROLOGY...24/NV

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