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/...
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.

&&

.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/...
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.

&&

.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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