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Area Forecast Discussion
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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/...
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.

&&

.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/...
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.

&&

.MARINE...
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.

&&

.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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