Area Forecast Discussion
Issued by NWS Upton, NY

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000 FXUS61 KOKX 030231 AFDOKX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW YORK NY 931 PM EST MON MAR 2 2015 .SYNOPSIS... HIGH PRESSURE BUILDS IN TONIGHT...DRIFTING OVER...THEN EAST OF THE REGION ON TUESDAY. LOW PRESSURE WILL TRACK WELL NORTH OF THE AREA TUESDAY NIGHT AND WEDNESDAY...WITH A WARM FRONT LIFTING TOWARDS THE AREA TUESDAY NIGHT...FOLLOWED BY A COLD FRONT WEDNESDAY. THE COLD FRONT SLIDES TO THE SOUTHEAST WEDNESDAY NIGHT...WITH WAVES OF LOW PRESSURE TRACKING ALONG IT INTO THURSDAY. CANADIAN HIGH PRESSURE THEN BUILDS IN THROUGH THURSDAY NIGHT...THEN SLIDES TO OUR SOUTH THROUGH FRIDAY NIGHT. A COLD FRONT APPROACHES FROM THE WEST SATURDAY...THEN CROSSES THE AREA SATURDAY NIGHT. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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HIGH PRES OVER THE OHIO VALLEY CONTINUES TO BUILD EAST. THE GRADIENT WILL RELAX THROUGH THIS EVENING...AND NW WINDS WILL GRADUALLY DIMINISH. MAINLY CLEAR SKIES ON TAP FOR THE OVERNIGHT WITH POSSIBLY SOME CIRRUS LATE. WINDS WILL BE LIGHT TO CALM. COMBINED WITH THE SNOWPACK...THINKING IS THAT AREAS ESPECIALLY AWAY FROM THE CITY WILL DROP A FEW DEGREES LOWER THAN A MAV/NAM MOS BLEND. KEPT OVERNIGHT LOWS A FEW DEGREES COLDER THAN THE COLDER MAV MOS FOR THESE SPOTS.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/... WAA BEGINS AS THE HIGH PRESSURE CENTER MOVES OFFSHORE. WITH THE WAA ALOFT...CLOUDS WILL QUICKLY LOWER AND THICKEN THROUGH THE DAY. AS HAS BEEN THE CASE THIS WINTER...OVERRUNNING PCPN PROBABLY ARRIVES A LITTLE SOONER THAN PROGGED BY THE MODELS. WILL THEREFORE MAINTAIN POPS INCREASING TO LIKELY/CATEGORICAL ACROSS THE AREA BY TUES EVENING...FOLLOWED BY CATEGORICAL POPS TUES NIGHT...THEN POPS LOWERING THROUGH THE DAY WITH A COLD FRONT PASSAGE. FOR QPF...NO SIGNIFICANT DIFFERENCES AMONG NAM/GFS/ECMWF/CANADIAN ALTHOUGH NAM IS SOMEWHAT A WETTER OUTLIER. WENT FAIRLY CLOSE TO RFC GUIDANCE...WHICH SEEMED TO BE CLOSE TO A BLEND OF THESE. FOR TEMPERATURES THROUGH THIS EVENT...DIDN`T STRAY TOO FAR FROM WHAT WAS ALREADY IN THE GRIDS. THINKING IS THAT SIMILAR TO THE PAST COUPLE EVENTS...SURFACE TEMPS WILL LIKELY BE LOWER THAN SHOWN BY MAV/NAM MOS...WITH SUNY SB HI-RES WRF CLOSER TO WHAT WILL PROBABLY HAPPEN. ALOFT...WOULDN`T BE SURPRISED TO SEE A COLDER TREND BY MODELS AS WE GET CLOSER TO THE EVENT. BUT EVEN SO...THINKING IS THAT THE MAX TEMP IN THE ELEVATED WARM LAYER WILL BE PLENTY WARM ENOUGH FOR AN EVENTUAL TRANSITION TO BRIEF SLEET AND FREEZING RAIN AFTER STARTING AS ALL SNOW...THEN CHANGING PLAIN RAIN. BY THE TIME SOME OF THE NW SUBURBS SURFACE TEMPS RISE ABOVE FREEZING...POPS SHOULD BE ON THE DOWNWARD TREND. ICING CONCERNS WILL THEREFORE BE THE GREATEST THERE. EXPECTING GENERALLY 1 TO 3 / 2 TO 4 INCHES OF SNOW ACROSS THE AREA ALONG WITH A TRACE UP TO A TENTH OF AN INCH OF ICE. ONLY SPOT WHERE ICING IS NOT FORECAST IS EASTERN SUFFOLK COUNTY...WHICH IS THE ONLY AREA THAT WILL NOT HAVE A WINTER WEATHER ADVISORY WITH THIS UPDATE. THE ADVISORY STARTS LATE TUESDAY AFTERNOON AND CONTINUES INTO LATE TUESDAY NIGHT INTO WEDS MORNING. PLAIN RAIN IS EXPECTED WEDNESDAY AFTERNOON ANYWHERE PCPN IS FALLING. HIGHS ON WEDNESDAY IN THE UPPER 30S TO AROUND 40. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... THERE IS THE POTENTIAL FOR WARNING LEVEL SNOWFALL ACROSS THE ENTIRE TRI-STATE FROM WEDNESDAY NIGHT INTO THURSDAY. THERE IS GENERAL MODEL AGREEMENT THAT THE COLD FRONT CROSSING THE AREA WEDNESDAY NIGHT BECOMES ANAFRONTAL IN NATURE AND THAT AT LEAST ONE WAVE OF LOW PRESSURE DEVELOPS ALONG THE FRONT NEAR THE MID-ATLANTIC COAST WEDNESDAY NIGHT AND TRACKS NORTHEAST INTO THURSDAY. THIS IS IN PART IN RESPONSE TO A NORTHERN STREAM TROUGH WHICH TRACKS FROM THE MIDWEST WEDNESDAY NIGHT TO THE NORTHEASTERN US BY THURSDAY EVENING. THERE ARE STILL DIFFERENCES IN THE DETAILS...INCLUDING EXACTLY HOW FAR SIGNIFICANT QPF GETS PUSHED INTO NW PORTIONS OF THE CWA...AND HOW FAST THE PRECIPITATION TURNS OVER TO ALL SNOW WEDNESDAY NIGHT. THE NAM IS THE SLOWEST TO COOL THE LOW LEVELS WEDNESDAY NIGHT...BUT HAS HAD A WARM BIAS OF LATE...THE GFS/ECMWF ARE THE FASTEST...WITH THE CMC SOMEWHERE IN BETWEEN. HAVE USED A GFS/ECMWF/CMC BLEND FOR THERMAL PROFILES WITH THIS SYSTEM...AND FOLLOWED FAIRLY CLOSE TO HPC QPF - REFER TO THE HYDROLOGY SECTION OF THE AFD FOR DETAILS. GENERALLY EXPECT RAIN TO CHANGE TO SNOW FROM NW TO SE BY AROUND MIDNIGHT...MAYBE A TAD SLOWER OVER THE TWIN FORKS AND NYC. THE HEAVIEST QPF AND HENCE SNOWFALL THOUGH WILL OCCUR FROM AROUND MIDNIGHT WEDNESDAY NIGHT THROUGH THURSDAY MORNING IN RESPONSE TO THE REGION BEING IN THE RIGHT REAR QUADRANT OF AN AROUND 200 KT 250 HPA JET. SNOW TAPERS OFF FROM NW TO SE LATE THURSDAY MORNING/AFTERNOON. AS NOTED IN THE OPENING TO THIS SECTION...HAVE THE POTENTIAL FOR AT LEAST 6 INCHES OF SNOW ACROSS THE ENTIRE AREA FROM WEDNESDAY NIGHT INTO THURSDAY - WITH THE BEST CHANCE OVER NYC/NE NJ/LONG ISLAND AND SE CT. THIS THREAT WILL BE HIGHLIGHTED IN THE HWO. THEREAFTER...NW FLOW ALOFT THURSDAY NIGHT GIVES WAY TO ZONAL FLOW BY FRIDAY NIGHT. A NORTHERN STREAM SHORTWAVE APPROACHES FROM THE W SATURDAY...THEN PASSES TO THE N SATURDAY NIGHT. WITH BEST FORCING CURRENTLY PROGGED TO THE N...HAVE KEPT THINGS DRY FOR NOW. THE ECMWF AND GFS THEN DIVERGE A BIT...WITH THE ECMWF MORE PROGRESSIVE...WITH ZONAL FLOW OR WEAK RIDGING...WHILE THE GFS HAS A MEAN TROUGH SETTING UP OVER THE EAST. THEY BOTH AGREE ON A NORTHERN STREAM SHORTWAVE APPROACHING MONDAY. GIVEN MIXED SIGNAL...AND GENERAL INDICATION THAT FOR NOW MORE LIKELY TO BE DRY THEN WET...WENT WITH A DRY FORECAST SUNDAY/SUNDAY NIGHT...THEN SLIGHT CHANCE POPS AHEAD OF THE SHORTWAVE ON MONDAY. HOWEVER...GIVEN CHANGEABILITY IN MODELS SO FAR THIS YEAR...WOULD NOT BE SURPRISED IF FORECAST CHANGES FROM THE ABOVE. WHAT IS MORE CERTAIN IS THAT TEMPERATURES THROUGH THE LONG TERM REMAIN BELOW NORMAL...WITH THURSDAY-FRIDAY QUITE COLD WITH TEMPERATURES AROUND 20 DEGREES BELOW NORMAL. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/...
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HIGH PRESSURE BUILDS TONIGHT AND PASSES OVERHEAD EARLY TUESDAY MORNING. A WARM FRONT APPROACHES TUESDAY NIGHT. VFR WITH MAINLY CLEAR SKIES TONIGHT. LINGERING GUSTS SHOULD END... AS NW WINDS DIMINISH. WINDS BECOME LIGHT AND VARIABLE TUESDAY MORNING WITH THE HIGH MOVING OVERHEAD AND THEN SE BY AFTERNOON. MID AND HIGH LEVEL CIGS WILL MOVE IN TOWARD DAYBREAK. BY LATE DAY...EXPECT CIGS TO LOWER TO MVFR IN LIGHT SNOW. .OUTLOOK FOR 00Z WEDNESDAY THROUGH SATURDAY... .TUESDAY NIGHT...IFR OR LOWER LIKELY. MIX OF SNOW AND SLEET CHANGING OVER TO ALL RAIN. LLWS LIKELY AFTER 06Z. .WEDNESDAY...MVFR OR LOWER POSSIBLE IN LIGHT RAIN IN THE MORNING. CONDITIONS MAY IMPROVE TO VFR IN THE AFT. LLWS POSSIBLE IN THE MORNING. .WEDNESDAY NIGHT-THURSDAY...MVFR OR LOWER POSSIBLE IN ANY PRECIPITATION...WITH A TRANSITION BACK TO SNOW. .THURSDAY NIGHT-FRIDAY...VFR. NW WINDS G15-20KT POSSIBLE THURSDAY NIGHT. .SATURDAY...VFR.
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&& .MARINE...
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SCA CONDS CONTINUE FOR WESTERN OCEAN WATERS/LI SOUND/NY HARBOR/LI BAYS UNTIL MIDNIGHT...AND FOR THE CENTRAL AND EASTERN OCEAN WATERS UNTIL 6 AM TUESDAY. 25 KT GUSTS WILL CONTINUE DURING THIS TIME...AND THEN SEAS WILL REMAIN ABOVE 5 FT FROM MIDNIGHT THROUGH DAYBREAK TUESDAY. FOR TUESDAY....A TRANQUIL PERIOD WITH HIGH PRESSURE PASSING OVER THE AREA...LEADING TO LIGHT WINDS. SCA CONDS THEN RETURN AT LEAST ON THE OCEAN WATERS TUESDAY NIGHT AND WEDNESDAY MORNING. SMALL CRAFT ADVISORY CONDITIONS ARE LIKELY ON THE COASTAL OCEAN WATERS FROM WEDNESDAY NIGHT AND THURSDAY...AND POSSIBLE THURSDAY NIGHT. SCA LEVEL SEAS COULD LINGER ON THE COASTAL OCEAN WATERS EAST OF MORICHES INLET INTO SATURDAY. ELSEWHERE...SUB-SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED FROM WEDNESDAY NIGHT THOUGH SATURDAY. THERE IS HOWEVER...A LOW CHANCE OF SCA LEVEL GUSTS ON THE NON-OCEAN WATERS THURSDAY NIGHT.
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&& .HYDROLOGY... BETWEEN ABOUT 1/2 TO 3/4 INCH OF LIQUID EQUIVALENT PCPN IS LIKELY LATE TUE THROUGH WED MORNING. SOME OF THIS WILL FALL AS PLAIN RAIN...THEREFORE THE COMBINATION OF THIS AND SOME MELTING SNOW PACK COULD CAUSE NUISANCE URBAN FLOODING ISSUES ACROSS THE METRO AND COASTAL PLAIN TUESDAY NIGHT INTO WEDNESDAY MORNING. FROM 1/3 OF AN INCH OVER FAR W ORANGE COUNTY TO AROUND 1 INCH OVER LONG ISLAND OF LIQUID EQUIVALENT IS EXPECTED TO FALL FROM WEDNESDAY NIGHT INTO THURSDAY. MOST IF NOT ALL OF THIS WILL FALL IN THE FORM OF SNOW. GIVEN THE UNCERTAINTY IN HOW FAST THE RAIN CHANGES TO SNOW OVER NE NJ/NYC/LONG ISLAND...MINOR FLOODING CANNOT BE COMPLETELY RULED OUT AT THIS TIME. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...WINTER WEATHER ADVISORY FROM 3 PM TUESDAY TO 10 AM EST WEDNESDAY FOR CTZ005>008-011-012. WINTER WEATHER ADVISORY FROM 3 PM TUESDAY TO 6 AM EST WEDNESDAY FOR CTZ009-010. NY...WINTER WEATHER ADVISORY FROM 3 PM TUESDAY TO 10 AM EST WEDNESDAY FOR NYZ067>070. WINTER WEATHER ADVISORY FROM 3 PM TUESDAY TO 6 AM EST WEDNESDAY FOR NYZ071. WINTER WEATHER ADVISORY FROM 3 PM TUESDAY TO 2 AM EST WEDNESDAY FOR NYZ072>075-078-080-176>179. NJ...WINTER WEATHER ADVISORY FROM 3 PM TUESDAY TO 10 AM EST WEDNESDAY FOR NJZ002-103. WINTER WEATHER ADVISORY FROM 3 PM TUESDAY TO 6 AM EST WEDNESDAY FOR NJZ004-104. WINTER WEATHER ADVISORY FROM 3 PM TUESDAY TO 2 AM EST WEDNESDAY FOR NJZ006-105>108. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR ANZ330-335- 338-340-345-355. SMALL CRAFT ADVISORY UNTIL 6 AM EST TUESDAY FOR ANZ350-353. && $$ SYNOPSIS...JC/MALOIT NEAR TERM...MPS SHORT TERM...JC LONG TERM...MALOIT AVIATION...PW MARINE...JC/MALOIT HYDROLOGY...JC/MALOIT

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