Area Forecast Discussion
Issued by NWS Upton, NY

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362 FXUS61 KOKX 042141 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 441 PM EST THU FEB 4 2016 .SYNOPSIS...
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WAVES OF LOW PRESSURE WILL DEVELOP ALONG A COLD FRONT AND PASS OFFSHORE TONIGHT AND FRIDAY. HIGH PRESSURE BUILDS IN FROM THE SOUTHWEST FRIDAY NIGHT INTO THE WEEKEND. FAIR WEATHER OVER THE WEEKEND WILL GIVE WAY TO A CHANCE FOR SNOW DURING THE BEGINNING OF NEXT WEEK. A COLD AIRMASS WILL THEN BRING TEMPERATURES TO BELOW NORMAL LEVELS FOR THE END OF THE WEEK.
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&& .NEAR TERM /THROUGH FRIDAY/...
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A COUPLE OF LOW PRESSURE WAVES PASS BY TO OUR SE ALONG A COLD FRONT TONIGHT AND FRIDAY. THE TWO WAVES WILL BRING PCPN TO MOST...IF NOT ALL OF THE CWA TONIGHT INTO TOMORROW MORNING. THE SECOND WAVE WILL BE ENHANCED BY A STRONG SHORTWAVE BEGINNING TO SHIFT THROUGH AS WELL AS SYNOPTIC LIFT COURTESY OF THE RIGHT REAR QUADRANT OF AN UPPER JET STREAK. MODELS OVER THE PAST COUPLE OF DAYS HAVE TRENDED WEST WITH QPF OUTPUT. HAVE GONE WITH A BLEND OF 12ZWPC/GGEM/NAM/GFS AND 00Z ECMWF WITH A FEW SLIGHT UPWARD ADJUSTMENTS. WITH THE CWA ON THE BACKSIDE AND NEAR THE EDGE OF THE PCPN SHIELD FOR THE ENTIRE EVENT ALONG WITH A NORTHERLY FLOW...THERE SHOULD BE A SOMEWHAT SHARP GRADIENT OF SNOWFALL TOTALS WITHIN THE FORECAST AREA. COMPLICATING THE SNOWFALL FORECAST IS THE TIMING OF WHEN THERMAL PROFILES COOL OFF ENOUGH FOR ALL SNOW. BASED ON THERMAL PROFILES AND WET BULB-ZERO HEIGHTS...PCPN STARTS AS RAIN TONIGHT. THEN AS COLDER AIR GETS DRAWN IN WITH A NORTH WIND...AN EVENTUAL MIX AND CHANGEOVER TO SNOW OCCURS DURING THE LATER HOURS. LOOKS LIKE BY DAYBREAK...MIXING COULD STILL BE OCCURRING OVER EASTERN LONG ISLAND...BUT OTHERWISE...SNOW ACROSS THE CWA. BASED ON MID-LEVEL FRONTOGENESIS FORECAST...BANDED SNOW IS POSSIBLE...BUT AS ALWAYS...THESE MESOSCALE FEATURES ARE HARD TO PIN DOWN. ANOTHER THING TO CONSIDER ARE THE MILD TEMPERATURES AT THE START OF THIS EVENT....AND THAT DYNAMIC COOLING COULD BE TEMPERED BY THE LACK OF A SIGNIFICANT DRY LAYER ALOFT. COMBINED WITH THE BANDING UNCERTAINTY...DO NOT HAVE THE CONFIDENCE TO ENHANCE SNOWFALL TOTALS ANYWHERE IN THE CWA AT THIS TIME...BUT AN EARLIER CHANGEOVER TO SNOW COULD RESULT IN AMOUNTS AT LEAST A COUPLE OF INCHES ABOVE THE CURRENT FORECAST. BEST CHANCE OF WARNING-LEVEL SNOWFALL WOULD BE OVER NEW LONDON COUNTY...BUT EVEN HERE HAVE GONE WITH A WINTER WEATHER ADVISORY. WINTER WEATHER ADVISORIES HAVE ALSO BEEN ISSUED FOR THE REST OF THE CWA WITH THE EXCEPTION OF ORANGE AND WESTERN PASSAIC COUNTIES. FOR TEMPS...WEIGHTED THEM TOWARD THE 2-METER NAM NUMBERS AS A MAV/NAM MOS BLEND IS USUALLY TOO HIGH IN THESE SITUATIONS. SKIES THEN BEGIN TO CLEAR OUT DURING FRIDAY AFTERNOON.
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&& .SHORT TERM /FRIDAY NIGHT/...
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MOSTLY CLEAR WITH HIGH PRESSURE BUILDING IN. LOW TEMPS ARE A MAV/NAM MOS BLEND.
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&& .LONG TERM /SATURDAY THROUGH THURSDAY/...
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A SFC HIPRES RIDGE EXTENDS NEWD INTO THE REGION SAT. DESPITE COLD TEMPS ALOFT WITH H85 AROUND -8C...SW FLOW THRU THE LAYER SHOULD ALLOW FOR DEEP MIXING BRINGING HI TEMPS AOA 40F. ON SUN...AN UPR LOW TRACKING ACROSS QUEBEC PROGGED TO DROP A CDFNT THRU DURING THE DAY. THE CAA APPEARS TOO LATE ATTM TO HAVE AND IMPACT ON HI TEMPS. ALTHOUGH THERE MAY BE SOME WEAK LIFT AND LIKELY TO BE SOME MID LVL MOISTURE WITH THE FRONT...THE SYS WILL BE BATTLING SUBSIDENCE. AS A RESULT...AGREED WITH THE MODEL CONSENSUS OF A DRY FROPA. A COUPLE OF QUESTIONS FOR THE BEGINNING OF NEXT WEEK. THE FIRST IS DEEP LOW PRES WHICH IS SPAWNED OFF THE SERN ATLC COAST AND TRACKS NEWD OVER THE OCEAN. THE GFS IS WAY OUT OF RANGE...WHILE THE ECMWF DESPITE A SLGT EWD TREND WITH THE 12Z RUN REMAINS CLOSE ENOUGH TO PERHAPS GRAZE THE TWIN FORKS. THIS STORM WILL NEED TO BE WATCHED BECAUSE THE MODEL DROPS IT INTO THE 970S. STILL...ONLY VERY LOW POPS FOR THIS STORM ATTM...WHICH ACTUALLY BLEEDS INTO THE NEXT SYS WHICH APPEARS MORE LIKELY TO IMPACT THE CWA. THIS ONE IS ROOTED IN A BROAD H5 LOW WHICH SPINS INTO THE NERN CONUS AND ALLOWS LOW PRES TO DEVELOP JUST OFFSHORE. BASED ON THE GEFS...A PROG CLOSER TO THE ECMWF APPEARS TO BE THE CONSENSUS ATTM. OR IN GFS TERMS...A LOW SLIGHTLY FURTHER S THAN THE OPERATIONAL 12Z RUN. POPS WERE INCREASED INTO THE 50 PERCENT RANGE FOR LATE MON THRU TUE. DID MAINTAIN SOME RAIN CHCS WITH THE SNOW IN CASE THE FURTHER NWD SOLN PANS OUT...BRINGING IN WARMER MARITIME AIR. THE CYCLONIC FLOW ALOFT COULD ALLOW FOR SOME RESIDUAL LGT SNOW ON WED...BUT CAPPED POPS AT 20 PERCENT DUE TO DOWNSLOPE FLOW COMPONENT. SUPERBLEND TEMPS THU APPEAR GOOD WITH A CHILLY PATTERN IN PLACE. AN ARCTIC SHOT POSSIBLE NEXT WEEKEND.
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&& .AVIATION /22Z THURSDAY THROUGH TUESDAY/...
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VFR CONDITIONS THROUGH THIS EVENING. N-NNW WINDS GENERALLY 7-11KT. -RA DEVELOPS FROM S TO N 03-04Z. -RA MIXES WITH -SN OVERNIGHT...AND CHANGES TO ALL -SN BY SUNRISE FOR NYC TERMINALS ALONG WITH IFR COND. SEVERAL HOURS OF MODERATE SNOW PSBL NYC TERMINALS EARLY FRIDAY MORNING. -SN GRADUALLY TAPERS OFF FROM W TO E MID-LATE MORNING...WITH COND IMPROVING TO MOSTLY VFR BY AFTERNOON. WINDS BECOME NRLY OVERNIGHT WITH GUSTS INCREASING TO 20-25KT BY SUNRISE...THEN BECOME MORE NWRLY DURING THE DAY FRIDAY. GUSTS OVER 25KT PSBL BY MID-LATE MORNING...PEAKING JUST SHORT OF 30KT. A FEW INCHES OF RUNWAY ACCUMULATION LIKELY NYC METRO TERMINALS...WITH SLIGHTLY HIGHER AMOUNTS POSSIBLE KISP/KGON. 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: NO UNSCHEDULED AMENDMENTS ANTICIPATED. KLGA FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS ANTICIPATED. KEWR FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS ANTICIPATED. KTEB FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS ANTICIPATED. KHPN FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS ANTICIPATED. KISP FCSTER COMMENTS: NO UNSCHEDULED AMENDMENTS ANTICIPATED. .OUTLOOK FOR 18Z FRIDAY THROUGH TUESDAY... .FRIDAY AFTERNOON...CONT IMPROVEMENT TO VFR. NW WIND GUSTS 25KT. .FRIDAY NIGHT-SUNDAY...VFR. SW WINDS G15-20KT POSSIBLE DURING THE DAY ON SATURDAY. .MONDAY-TUESDAY...MAINLY VFR EARLY MONDAY. MVFR OR LOWER POSSIBLE LATE MONDAY-TUESDAY WITH CHANCE OF LIGHT SNOW.
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&& .MARINE...
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WINDS AND SEAS INCREASE WITH OFFSHORE LOW PRESSURE. SCA CONDS WILL INCREASE TO GALES ON THE OCEAN DURING FRIDAY. ELSEWHERE...HAVE GONE WITH SCA DURING THE DAY FRIDAY. RAFT LEVELS TODAY INTO TONIGHT. THEREFORE THE ADVISORY HAS BEEN EXTENDED THROUGH FRIDAY. SOME RESIDUAL SCA CONDITIONS ON THE OCEAN FOR EARLY FRIDAY NIGHT. OTHERWISE...CONDITIONS TREND TO BELOW SCA LATER ON FRIDAY NIGHT AND CONTINUING THROUGH THE WEEKEND WITH HIGH PRESSURE FROM THE SOUTHWEST BUILDING IN. CONDITIONS BECOME MORE ROUGH NEXT WEEK WITH THE POTENTIAL WAVES OF LOW PRESSURE. SCA WILL BE MORE PROBABLE IN THIS TIMEFRAME.
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&& .HYDROLOGY...
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TONIGHT INTO FRIDAY...ONE QUARTER OF AN INCH TO AN INCH AND A QUARTER OF LIQUID EQUIVALENT PCPN IS EXPECTED. HIGHEST AMOUNTS WILL BE OVER EASTERN LONG ISLAND AND SE CT. LOWEST AMOUNTS ACROSS NE NJ AND THE LOWER HUDSON VALLEY. PCPN STARTS OUT AS RAIN...BUT SHOULD BE CHANGING TO SNOW FOR MOST SPOTS BY DAYBREAK FRIDAY. NO HYDROLOGIC IMPACTS EXPECTED. WIDESPREAD MEASURABLE PCPN POSSIBLE LATE MON THRU TUE. MOST OF THAT COULD BE IN THE FORM OF SNOW.
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&& .OKX WATCHES/WARNINGS/ADVISORIES...
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CT...WINTER WEATHER ADVISORY FROM 1 AM TO 1 PM EST FRIDAY FOR CTZ007-008-011-012. WINTER WEATHER ADVISORY FROM 1 AM TO 10 AM EST FRIDAY FOR CTZ005-006-009-010. NY...WINTER WEATHER ADVISORY FROM 1 AM TO 1 PM EST FRIDAY FOR NYZ079-081. WINTER WEATHER ADVISORY FROM 1 AM TO 10 AM EST FRIDAY FOR NYZ068>075-078-080-176>179. NJ...WINTER WEATHER ADVISORY FROM 1 AM TO 10 AM EST FRIDAY FOR NJZ004-006-103>108. MARINE...SMALL CRAFT ADVISORY FROM 6 AM TO 6 PM EST FRIDAY FOR ANZ330- 335-338-340-345. SMALL CRAFT ADVISORY UNTIL 6 AM EST FRIDAY FOR ANZ350-353-355. GALE WARNING FROM 6 AM TO 6 PM EST FRIDAY FOR ANZ350-353-355.
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&& $$ SYNOPSIS...JMC/JC NEAR TERM...JC SHORT TERM...JC LONG TERM...JMC AVIATION...GS MARINE...JMC/JC HYDROLOGY...JMC/JC

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