-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KOKX 282353
AFDOKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
653 PM EST SAT FEB 28 2015

.SYNOPSIS...
HIGH PRESSURE OVER THE AREA SLIDES OFFSHORE INTO SUNDAY. A COLD
FRONT APPROACHES FROM THE WEST LATE SUNDAY...THEN CROSSES THE
AREA SUNDAY NIGHT. HIGH PRESSURE BUILDS IN FROM THE WEST ON
MONDAY AND SLIDES OFFSHORE ON TUESDAY. LOW PRESSURE WILL TRACK WELL
NORTH OF THE AREA TUESDAY NIGHT AND WEDNESDAY...WITH A WARM FRONT
LIFTING INTO THE AREA TUESDAY NIGHT...FOLLOWED BY A COLD FRONT
WEDNESDAY AND ANOTHER SURFACE TROUGH LATE WEDNESDAY NIGHT. HIGH
PRESSURE THEN BUILDS IN FOR THE REMAINDER OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --
850-500 HPA SHORTWAVE RIDGING CROSSES THE AREA TONIGHT...KEEPING
THINGS DRY. IT WILL ALSO KEEP THE AREA RELATIVELY CLOUD FREE UNTIL
THE RIDGE AXIS PASSES OVERNIGHT.

FORECAST IS GENERALLY ON TRACK. INCREASED LOWS A FEW DEGREES
TONIGHT WITH MID AND HIGH CLOUDS EXPECTED TO MOVE IN DURING THE
LATTER PART OF THE NIGHT. WINDS WILL BECOME LIGHT AND VRB TO CALM
WITH CLEAR SKIES PROMOTING EXCELLENT RADIATIONAL COOLING CONDS.
TEMPS WILL DROP LIKE A ROCK ONCE THIS OCCURS. GUIDANCE NEVER
CAPTURES THIS WELL...SO HOURLY T ARE DIFFICULT TO FORECAST.

LOWS ARE FORECAST TO BE AROUND 15-20 DEGREES BELOW NORMAL -
MAINLY IN THE SINGLE DIGITS...EXCEPT 10-15 NYC AND WESTERN LONG
ISLAND. THERE COULD BE A FEW AREAS IN FAR N INTERIOR ZONES THAT
DIP JUST BELOW ZERO. WINDS WILL BE LIGHT...SO WIND CHILLS WILL BE
AT IF NOT SLIGHTLY BELOW THE AIR TEMPERATURE.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/...
MODELS ARE ALL IN GOOD AGREEMENT ON THE GENERAL PATTERN SUNDAY-
MONDAY...BUT DIFFER IN DETAILS...PARTICULARLY AT THE SURFACE.

GIVEN WESTERLY FLOW AND WARM ADVECTION PATTERN ON SUNDAY...EXPECT
PRECIPITATION TO DEVELOP AS FAST IF NOT FASTER THAN THE FASTEST
MODEL...WHICH IS THE GFS. HAVE INCREASED POPS TO CATEGORICAL BY
LATE AFTERNOON AS A RESULT. REGARDLESS OF MODEL OF CHOICE...ONLY
SEE SNOW AS THE P-TYPE DURING THE DAY ON SUNDAY.

HAVE SIDED WITH HIGHER RESOLUTION...ESPECIALLY IN THE
VERTICAL...ECMWF/NAM /CMC-REG AND TO A LESSER EXTENT THE SREF
WITH THE IDEA OF A COASTAL FRONT DEVELOPING TO THE S OF LONG
ISLAND SUNDAY NIGHT...WITH A WEAK LOW OF PRESSURE RIDING ALONG IT
AND PASSING TO THE S OF LONG ISLAND. THIS IS A FEATURE THAT HAS
BEEN OBSERVED IN MULTIPLE OTHER STORMS WITH A SIMILAR PATTERN
THIS WINTER...AND HAVE NO REASON TO BELIEVE THAT THIS TIME WILL
BE ANY DIFFERENT.

THE IMPACT OF THIS COASTAL FRONT WITH THE WAVE OF LOW PRESSURE
GOING ALONG IT...WILL BE TO HELP KEEP THE LOW LEVEL COLD AIR IN
PLACE THROUGH MOST OF SUNDAY NIGHT OVER THE CWA. AS A RESULT DO
NOT HAVE ANY AREA MIXING WITH OR CHANGING TO RAIN...HOWEVER STILL
EXPECT NYC/LONG ISLAND/MOST OF NE NJ/S WESTCHESTER AND FAIRFIELD
TO MIX WITH/CHANGE TO ZR LATE SUNDAY EVENING.

WITH THE FASTER ONSET...ALSO HAVE A FASTER END TIME...WIT
PRECIPITATION COMING TO AN END FROM W TO E AFTER MIDNIGHT SUNDAY
NIGHT.

BASED ON THIS...EXPECT 2-5 INCHES OF SNOW WITH UP TO A TENTH OF
AN INCH OF ICE ACROSS NYC/LONG ISLAND/NE NJ/COASTAL WESTCHESTER
AND FAIRFIELD. EXPECT 3-6 INCHES OF SNOW ELSEWHERE...EXCEPT FOR
POSSIBLY 4-7/MAYBE 8 INCHES ACROSS NEW HAVEN/MIDDLESEX/NEW LONDON
COUNTIES. THEREFORE HAVE ISSUED A WINTER STORM WATCH FROM NEW
HAVEN COUNTY ON E IN S CT...AND A WINTER WEATHER ADVISORY
ELSEWHERE IN THE CWA.

STILL SOME UNCERTAINTY ON QPF - WITH NAM/SREF WETTEST AND GFS
GENERALLY THE DRIEST...WITH THE CMC AND ECMWF IN BETWEEN...AND
TIMING. ALSO STILL SOME UNCERTAINTY ON TIMING OF ANY MIX/CHANGE
OVER TO ZR...AND IF COASTAL FRONT WILL INDEED STAY S OF LONG
ISLAND AS CURRENTLY FORECAST.

TEMPERATURES SUNDAY/SUNDAY NIGHT A BLEND OF MAV/MET/ECS GUIDANCE
AND NAM 2-METER TEMPERATURES...WITH AN ADJUSTMENT FOR WET-BULBING
BASED ON A MAV/MET BLENDED DEW POINT WHILE PRECIPITATING.
TEMPERATURES GENERALLY REACH MID 20S-LOWER 30S BEFORE THE ONSET
OF PRECIPITATION...THEN COOL TO THE LOWER 20S-AROUND 30 DURING THE
EVENT SUNDAY EVENING. COULD SEE A SLIGHT RISE IN TEMPERATURES LATE
SUNDAY NIGHT AFTER THE PRECIPITATION COMES TO AN END.

MONDAY SHOULD BE DRY WITH DOWN SLOPING BOUNDARY LAYER
FLOW...DESPITE PASSAGE OF 500 HPA TROUGH AXIS. HIGHS MONDAY
SHOULD BE AROUND 5-10 DEGREES BELOW NORMAL...WITH ALL BUT
POSSIBLY HIGHER ELEVATIONS BREAKING THE FREEZING MARK. GUSTY NW
WINDS MONDAY WITH GUSTS BY AFTERNOON UP TO 25-35 MPH WITH SOME
ISOLATED GUSTS TO 40 MPH POSSIBLE.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
MODELS ARE IN DECENT AGREEMENT AT H5 THROUGH THE WEEK...ALTHOUGH
SLIGHT DIFFERENCES IN HEIGHTS BEGIN TO TAKE SHAPE DURING THE LATTER
HALF FROM A DIGGING TROF IN THE MIDDLE OF THE COUNTRY.

RIDGING AT THE SFC AND ALOFT TRACKS TOWARDS THE E COAST MON NIGHT
WITH THE UPPER RIDGE AXIS SLIDING E TUE AFTN. PCPN WILL OVERSPREAD
THE AREA BY TUE EVENING AS SNOW...BUT WITH INCREASING S-SW WINDS AND
STRONG WAA TEMPS WILL WARM TUE NIGHT WITH SNOW CHANGING OVER TO RAIN
FROM S TO N. WARM FRONT LIFTING TOWARDS THE AREA TUE NIGHT...BUT
THERE IS SOME UNCERTAINTY IF THE LLJ WILL BE STRONG ENOUGH TO PUSH
IT THROUGH AT THE SFC. CLIMATOLOGY SAYS NO WITH THE LOW SO FAR TO
THE NW...SO TEMPS IN THE MID TO UPPER 40S MAY BE TOO HIGH.
HOWEVER...DO THINK TEMPS SHOULD BE ABOVE FREEZING BUT HOW MUCH
WILL DEPEND ON THE AMOUNT OF MELTING OF THE SNOWPACK. THIS...IN
ADDITION TO RAINFALL COULD LEAD TO MINOR FLOODING ISSUES. COLD
FRONT MOVES ACROSS WED FOLLOWED BY ANOTHER BOUNDARY LATE WED
NIGHT. THE NORTHERN EDGE OF THE PCPN SHIELD OF A SOUTHERN STREAM
SYSTEM RIDING ALONG THIS SECONDARY BOUNDARY COULD KEEP PCPN
LINGERING INTO THU...ALTHOUGH THE TREND HAS BEEN S OVER THE LAST
12 HOURS. HAVE KEPT CHC POPS FOR NOW. COLD WEATHER ALSO RETURNS IN
THE WAKE OF THIS SECOND BOUNDARY.

STRONG CANADIAN HIGH PRES THEN BUILDS TOWARDS THE AREA INTO THE
WEEKEND WITH DRY WEATHER BUT THE WELL BELOW NORMAL TEMPS
CONTINUING.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
HIGH PRESSURE TONIGHT WILL WEAKEN SUNDAY MORNING AS A WARM FRONT
APPROACHES.

EXPECT VFR CONDITIONS THROUGH EARLY SUNDAY MORNING...THEN VSBY
RAPIDLY LOWERS TO IFR DURING MID TO LATE MORNING AS LIGHT SNOW
DEVELOPS. THE SNOW PICKS UP IN INTENSITY AFTER 20Z FROM WEST TO
EAST...WITH LIFR POSSIBLE.

WINDS SHOULD BECOME LIGHT/VARIABLE OR CALM THIS EVENING AS THE HIGH
PASSES OVERHEAD...THEN LIGHT SOUTHERLY WINDS ARE FORECAST BY LATE
SUNDAY MORNING OR EARLY SUNDAY AFTERNOON.

.OUTLOOK FOR 00Z MONDAY THROUGH WED...

.SUNDAY NIGHT...MVFR/IFR CONDITIONS EXPECTED. SNOW...CHANGING TO A
WINTRY MIX AT KJFK/KEWR DURING THE EVENING...THEN AT THE REST OF THE
NYC METRO TERMINALS AFTER MIDNIGHT. MOST LIKELY TOTAL RUNWAY
ACCUMULATIONS...
KGON...5-7 INCHES.
KSWF/KHPN/KBDR...4-6 INCHES.
KEWR/KTEB/KLGA...2-4 INCHES.
KJFK/KISP...2-3 INCHES.

.MON-MON NIGHT...BECOMING VFR EARLY. NW WINDS 15-20 KT WITH GUSTS
25-35 KT FROM LATE MORNING UNTIL AROUND SUNSET.

.TUE...CHANCE OF SNOW WITH MVFR OR IFR CONDITIONS IN THE
AFTERNOON AT THE NYC METRO AND LOWER HUDSON VALLEY TERMINALS. VFR
FARTHER EAST.

.TUE NIGHT...IFR CONDITIONS LIKELY. SNOW...CHANGING TO A WINTRY
MIX AFTER MIDNIGHT...AND THEN RAIN LATE AT ALL TERMINALS EXCEPT
KSWF. LLWS POSSIBLE AFTER MIDNIGHT.

.WED...IFR CONDITIONS POSSIBLE IN RAIN...WITH FREEZING RAIN
CHANGING TO RAIN AT KSWF...AND PLAIN RAIN ELSEWHERE. LLWS
POSSIBLE IN THE MORNING.

.WED NIGHT...MVFR CONDITIONS LIKELY...IFR CONDITIONS POSSIBLE.
RAIN...MIXING WITH OR CHANGING TO SNOW AFTER MIDNIGHT.

.THU...CHANCE OF SNOW AND RAIN WITH MVFR CONDITIONS
POSSIBLE...ENDING BY NIGHTFALL.
-- End Changed Discussion --

&&

.MARINE...
A RELAXED PRESSURE GRADIENT WILL KEEP CONDITIONS BELOW SMALL
CRAFT LEVELS THROUGH SUNDAY NIGHT WITH WINDS 10 KT OR LESS ON ALL
WATERS THROUGH THEN.

WINDS INCREASE RAPIDLY OUT OF THE NW MONDAY AS LOW PRESSURE
DEEPENS TO THE NORTHEAST. ALL WATERS WILL SEE AT LEAST GUSTS TO
SCA LEVELS WITH A SMALL CHANCE TO CHANCE OF GALE GUSTS AS WELL.
WILL HIGHLIGHT THIS POTENTIAL IN THE HWO.

SUB-ADVSY CONDS RETURN LATE MON NIGHT AND CONTINUE THROUGH TUE.
SCA CONDS THEN RETURN TUE NIGHT DUE TO AN INCREASING SLY FLOW
AHEAD OF A WARM FRONT AND THEN BEHIND A COLD FROPA ON WED. GUSTS
DIMINISH WED NIGHT...BUT SEAS ON THE OCEAN WATERS WILL LINGER INTO
THU.

&&

.HYDROLOGY...
THERE IS THE POTENTIAL FOR AROUND 4-6 TENTHS OF AN INCH OF LIQUID
EQUIVALENT TO FALL SUNDAY AND SUNDAY NIGHT. WITH ALL OF THIS
EXPECTED TO BE EITHER FROZEN OR FREEZING PRECIPITATION...NO
IMMEDIATE HYDROLOGIC IMPACT IS EXPECTED.

BETWEEN 1/2 TO 1 INCH OF LIQUID EQUIVALENT PCPN IS POSSIBLE LATE
TUE THROUGH WED. MOST OF THIS WILL FALL AS RAIN...THEREFORE THE
COMBINATION OF THIS AND A MELTING SNOWPACK COULD CAUSE MINOR
FLOODING ISSUES.

ICE WILL CONTINUE TO DEVELOP ON LOCAL AREA RIVERS AND STREAMS AS
TEMPERATURES REMAIN WELL BELOW AVERAGE.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...WINTER WEATHER ADVISORY FROM 10 AM SUNDAY TO 7 AM EST MONDAY
     FOR CTZ005-009.
     WINTER STORM WATCH FROM SUNDAY MORNING THROUGH MONDAY MORNING
     FOR CTZ006>008-010>012.
NY...WINTER WEATHER ADVISORY FROM 10 AM SUNDAY TO 7 AM EST MONDAY
     FOR NYZ067>075-078>081-176>179.
NJ...WINTER WEATHER ADVISORY FROM 10 AM SUNDAY TO 7 AM EST MONDAY
     FOR NJZ002-004-006-103>108.
MARINE...NONE.

&&

$$