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Area Forecast Discussion
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000
FXUS61 KOKX 010258
AFDOKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
958 PM EST SAT JAN 31 2015

.SYNOPSIS...
HIGH PRESSURE BRIEFLY BUILDS IN TONIGHT...BEFORE A COLD FRONT
APPROACHES AND CROSSES ON SUNDAY. LOW PRESSURE APPROACHES FROM
THE OHIO VALLEY AND PASSES JUST SOUTH OF LONG ISLAND MONDAY. THE
LOW TRACKS WELL TO THE EAST MONDAY NIGHT WITH HIGH PRESSURE
BUILDING IN ITS PLACE. HIGH PRESSURE WILL LARGELY PREVAIL FOR THE
REMAINDER OF THE WEEK WITH THE EXCEPTION OF A COLD FRONTAL PASSAGE
LATE WEDNESDAY. A DEVELOPING LOW OVER THE GULF COAST STATES LATE
IN THE WEEK LOOKS TO TAKE A TRACK WELL SOUTH AND EAST OF THE AREA.

&&

.NEAR TERM /THROUGH SUNDAY/...
MINOR CHANGES MADE TO REFLECT CURRENT OBSERVATIONS...OTHERWISE
FORECAST IS ON TRACK. 

NEAR ZONAL FLOW TONIGHT WITH WEAK HIGH PRESSURE BUILDING IN FROM THE 
WEST THIS EVENING...AND THEN A POLAR FRONT APPROACHING FROM THE 
GREAT LAKES. 

WINDS AND GUSTS GRADUALLY SUBSIDE THROUGH MIDNIGHT...WITH INCREASING 
HIGH CLOUDS OVERNIGHT. 

TEMPS WILL NOT BE QUITE AS COLD WITH LOWS GENERALLY IN THE 
TEENS...EXCEPT 20S NYC/NJ METRO...WITH NEUTRAL TEMPS ADVECTION AND 
LIMITED OPPORTUNITY FOR RADIATIONAL COOLING. COULD SEE SOME SINGLE 
DIGITS IN PINE BARRENS AND INTERIOR TRI-STATE WITH DECOUPLING BEFORE 
CLOUDS MOVE IN.

PHASING NORTHERN STREAM AND SW US SHORTWAVE ENERGY BEGINS TO DIG 
INTO THE CENTRAL US ON SUNDAY WITH GENERALLY WSW UPPER FLOW.

A WEAKENING POLAR FRONT APPROACHES THE REGION ON SUNDAY...BUT 
OTHERWISE INCREASING AND LOWERING CLOUDS AHEAD OF NEXT APPROACHING 
STORM SYSTEM. A FEW SNOW FLAKES MAY BE OBSERVED OVER NJ VERY LATE IN 
THE DAY. TEMPS GENERALLY IN THE UPPER 20S TO LOWER 30S.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY/...
MAIN STORY WILL BE NEXT IN A SERIES OF WINTER STORMS AFFECTING THE
REGION SUNDAY NIGHT INTO MONDAY.

MODELS ARE IN GENERAL AGREEMENT WITH LOW PRESSURE TAKING SHAPE
OVER THE CENTRAL PLAIN TONIGHT...TRACKING INTO THE OHIO VALLEY ON
SUNDAY AND THEN JUST SOUTH OF THE REGION SUNDAY NIGHT. OVERALL
TREND HAS BEEN SLIGHTLY FURTHER NORTH AND WETTER WITH THIS SYSTEM.

BASED ON COUPLED JET STRUCTURE...TIGHT LOW /MID-LEVEL THERMAL
STRUCTURE...AND GULF MOISTURE FEED OF 2-3 STD PWATS...CONFIDENCE
IS HIGH IN AT LEAST A 3/4 TO 1 1/2 INCH QPF EVENT FOR THE ENTIRE
AREA. THIS IS BORNE OUT IN SREF/GEFS/CMCE 1 INCH/24 HR QPF PROBS.

SIGNIFICANT UNCERTAINTY LIES IN P-TYPE...PARTICULARLY ALONG THE
COAST...WITH A SPREAD OF ABOUT 50 MILES BETWEEN OPERATIONAL
SOLUTIONS AND ENSEMBLE MEANS IN HOW CLOSE TO THE COAST THE LOW
GETS AND THE POSITION OF THE TIGHT THERMAL GRADIENT ACROSS THE
REGION. SBU ENSEMBLE SENSITIVITY SHOWING THIS N/S TRACK UNCERTAINTY
IN THE 00Z GEFS/CMCE/ECMWF ENSEMBLES...WITH SENSITIVITY LYING IN
DEGREE OF PHASING/INTERACTION BETWEEN NORTHERN STREAM SHORTWAVE
ENERGY DROPPING DOWN THROUGH MONTANA AND THE CUTOFF UPPER LOW OVER
THE SW US...AND RESULTANT STRENGTH OF TROUGH APPROACHING THE EAST
COAST SUNDAY NIGHT/MONDAY AND UPSTREAM RIDGING. A STRONGER
TROUGH...MEANING MORE UPSTREAM RIDGING...AND A FURTHER NORTH
TRACK. THIS INTERACTION IS NOT COMPLETE FOR ANOTHER 24 HOURS...SO
COULD TAKE UNTIL THEN FOR CONFIDENCE IN P-TYPE FORECAST INCREASES.

WITH CONFLUENT FLOW ACROSS NORTHERN NEW ENGLAND/SE CANADA...ARCTIC 
HIGH SHOULD BE LOCKED INTO THAT AREA. PREFER TIGHTER THERMAL 
STRUCTURE ALOFT OF NAM/ECMWF/CAN VERSUS MORE DIFFUSE THERMAL 
STRUCTURE OF GFS IN THIS SITUATION...BUT QUESTION IS LOCATION OF 
THIS BAROCLINIC ZONE. MODEL SOLUTIONS POINTING TO DIFFERING
DEGREES OF WARMING IN THE 800-950 LAYER MON MORNING INTO EARLY
AFT...BUT TREND IS TOWARDS MORE WARMING.

WITH THIS SAID...NORTHWEST TIER OF THE TRI-STATE LOOKS TO BE
MAINLY SNOW. BIGGEST FORECAST CHALLENGE IS FOR COAST...ESPECIALLY
NYC/NJ/LI...IN AMOUNT OF SLEET/FZRA/RA VERSUS SNOW. 12Z GFS/GEFS
ARE FURTHER NORTH WITH LOW TRACK...JUST SOUTH OF LI MONDAY
AFTERNOON...WHICH WOULD IMPLY MORE IN THE WAY OF WARMING
ALOFT...AND MORE IN WAY MIXING WITH SLEET AND FREEZING RAIN AND
EVEN RAIN FOR LI/NYC. 12Z GEM HAS TRENDED IN THAT DIRECTION AS
WELL. 12Z NAM...WOULD POINT TO MAINLY SNOW FOR CT AND LOWER HUDSON
VALLEY...WITH A MIX OF SIGNIFICANT SNOW/SLEET ACCUM FOR
NYC/LI/METRO NJ. 00Z ECMWF...IS SIMILARLY COLDER AND A BIT FARTHER
SOUTH AS WITH THE NAM. HAVE TAKEN A MIDDLE OF THE ROAD SOLUTION
BASED ON THE UNCERTAINTY...WITH A SLIGHTLY WETTER AND WARMER
FORECAST. 

EVEN WITH CONTINUED NORTHWARD TREND...HIGHEST CONFIDENCE IN
SIGNIFICANT SNOW/SLEET/ICE ACROSS INTERIOR NE NJ...AND MOST OF THE
LOWER HUDSON VALLEY AND CT. HAVE UPGRADED TO WARNING THERE FOR 5
TO 10 INCHES OF SNOW/SLEET AND UP TO 1/4 INCH OF ICE. INTERIOR
PORTIONS OF LOWER HUDSON VALLEY AND SW CT...MORE IN THE 8 TO 14
INCH RANGE WITH LESS ICE/SLEET.

EVEN FOR NYC/NJ METRO AND LI...COULD SEE A QUICK 3 TO 5 INCH
SNOWFALL ON THE FRONT END WITH SOUTHERN STREAM MOISTURE AND STRONG
LIFT LATE SUN NIGHT/EARLY MON MORNING BEFORE ANY MIXING. AFTER
CHANGEOVER...A PROLONGED PERIOD OF FZRA/SLEET (1/4 INCH OF ICE)
POSSIBLE FOR NORTHERN HALF OF LI/NYC AND NE NJ...WITH COLD AIR
DRAINAGE DOWN THE RIVER VALLEYS. HAVE MAINTAINED A WATCH HERE WITH
UNCERTAINTY IF WE CHANGEOVER TO MORE RAIN...PARTICULARLY FOR SOUTH
COASTAL AREAS. THE ONE ASPECT TO KEEP IN MIND IS IF COASTAL AREAS
DO GO OVER TO RAIN...THERE IS POTENTIAL FOR URBAN FLOODING ISSUES.
SEE HYDROLOGY SECTION FOR MORE INFO.

ANY RAIN/MIXED PRECIP SHOULD GRADUALLY CHANGE BACK TO SNOW FROM NW
TO SE MONDAY AFTERNOON/EVE. EVEN SOME SIGNAL OF DEFORMATION BANDING
ON THE BACKSIDE...WITH ACCUMULATING SNOW BACK DOWN TO THE COAST.
WITH COLD AIR CRASHING BACK DOWN TO THE COAST...POTENTIAL FOR
FLASH FREEZE CONDITIONS FOR MONDAY EVENING COMMUTE FOR CITY/COAST
IN WAKE OF A WASHING RAIN. SO TO SAY THE LEAST...A COMPLICATED
FORECAST FOR THE NYC/NJ METRO AND LONG ISLAND...WHICH COULD STILL
SEE SIGNIFICANT IMPACTS EVEN IF IT IS NOT ALL FROZEN.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
A BROAD UPPER TROF WILL REMAIN IN PLACE THROUGH THE UPCOMING WEEK 
FROM THE CANADIAN PRAIRIE PROVINCES OF WESTERN CANADA SE INTO THE 
MID ATLANTIC REGION. THIS WILL KEEP A STEADY STREAM OF POLAR AIR 
MASSES MOVING ACROSS THE REGION WITH GENERALLY UNSEASONABLY COLD 
CONDITIONS. THIS SEASON HAS BEEN TYPIFIED BY THIS FLOW REGIME WITH 
NO BLOCK OVER GREENLAND. OCCASIONALLY...A STRONG SHORT WAVE BRIEFLY 
AMPLIFIES THE FLOW...BUT REMAINS PROGRESSIVE. 

THE ONLY CHANCE FOR PCPN LOOKS TO BE WITH A POLAR COLD FRONT WED 
INTO WED NIGHT...WHICH WILL BE IN THE FORM OF SCT SNOW SNOW SHOWERS. 
MODELS HAVE TRENDED WELL SOUTH AND EAST WITH A LATE WEEK COASTAL LOW 
MOVING OUT OF THE GULF COAST STATES. THUS...HAVE TRENDED DOWN TO THE 
POINT WHERE THERE IS NO MENTION OF PCPN LATE IN THE WEEK. 
INTERESTINGLY ENOUGH THOUGH...MODELS HAVE BEEN WAVERING BACK AND 
FORTH WITH THESE SYSTEMS...SO PERHAPS NOT COMPLETELY OUT OF THE 
WOODS. 

THE ONLY DAY OF THE WEEK THAT LOOKS TO BE NEAR NORMAL WITH RESPECT 
TO TEMPS IS WED AHEAD OF THE NEXT COLD FRONT.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
  **HIGH IMPACT EVENT SUNDAY NIGHT THROUGH MONDAY**

HIGH PRESSURE OVER THE TERMINALS THIS EVENING WEAKENS TONIGHT AS A 
WARM FRONT AND ASSOCIATED LOW PRESSURE APPROACH. THE WARM FRONT WILL 
BE IN THE VICINITY BY 00Z MONDAY. LIGHT SNOW WILL BE DEVELOPING LATE 
IN THE AFTERNOON MAINLY WEST OF THE NYC TERMINALS...AND BECOME 
LIKELY AROUND 00Z MONDAY WITH CONDITIONS LOWERING TO IFR. THERE IS 
STILL SOME UNCERTAINTY AS TO THE TIMING OF THE BEGINNING OF THE 
SNOW.

GUSTY NORTHWEST WIND SUBSIDE BY 03Z WITH THE WIND BECOMING MORE 
WESTERLY...GENERALLY UNDER 10 KT.

.OUTLOOK FOR 00Z MONDAY THROUGH THURSDAY...
.SUNDAY NIGHT-MONDAY...HIGH IMPACT PERIOD. IFR HIGHLY LIKELY AS SNOW 
DEVELOPS SUNDAY EVENING...THEN CONTINUES THROUGH THE OVERNIGHT. A 
WINTRY MIX OF  SLEET...SNOW AND FREEZING RAIN BECOMES LIKELY EARLY 
MONDAY MORNING AT THE NYC METRO TERMINALS AND ACROSS LONG ISLAND. 
THE WINTRY MIX PUSHES FARTHER NORTH DURING MONDAY MORNING AND 
CONTINUES INTO THE AFTERNOON BEFORE GOING BACK TO ALL SNOW BEFORE 
ENDING MONDAY EVENING.
.MONDAY NIGHT...BECOMING VFR AS SNOW COMES TO AN END. N-NW WIND 15 
TO 20 KT WITH GUSTS UP TO 30 KT.
.TUESDAY...VFR.
.WEDNESDAY...VFR. A CHANCE OF SNOW SHOWERS WEDNESDAY AFTERNOON AND 
WEDNESDAY NIGHT WITH LOCALLY MVFR TO IFR CONDITIONS.
.THURSDAY...VFR. NW GUSTS 20 KT.

&&

.MARINE...
SCA HAS BEEN CANCELLED ACROSS LONG ISLAND SOUND...PECONIC AND
GARDINERS BAYS...AND THE SOUTH SHORE BAYS AS WIND GUSTS HAVE
DIMINISHED TO LESS THAN 25 KT IN THESE AREAS.

SCA CONDITIONS CONTINUE FOR ALL OTHER MARINE ZONES FOR THE REST
OF THE NIGHT WITH A GRADUALLY DIMINISHING NW FLOW. 5 TO 9 FT SEAS
WILL GRADUALLY SUBSIDE TO LESS THAN 5 FT DURING THE OVERNIGHT
HOURS.

TRANQUIL CONDS ON THE WATERS SUN AS HIGH PRES BUILDS OVERHEAD AND 
DEPARTS. CONDS RAMP UP TO SMALL CRAFT ADVISORY LEVELS LATE SUNDAY 
NIGHT INTO MONDAY MORNING AHEAD OF APPROACHING LOW PRESSURE. A FEW 
GALE GUSTS MAY BE POSSIBLE ON THE OCEAN. 

THERE IS THE POTENTIAL FOR A MARGINAL GALE EVENT MON NIGHT ON THE
BACKSIDE OF DEEPENING LOW PRESSURE LIFTING UP INTO THE CANADIAN
MARITIMES. WINDS AND SEAS ARE THEN FORECAST TO SUBSIDE BELOW SCA
LEVELS ON TUE WITH HIGH PRESSURE BUILDING ACROSS THE WATERS.
MARGINAL SCA CONDITIONS ARE POSSIBLE ON THE OCEAN WATERS WED IN A
PRE-FRONTAL SW FLOW...AND THEN IN THE NW POST-FRONTAL FLOW ON THU.

&&

.HYDROLOGY...
GENERALLY 1 TO 1 1/2 INCHES OF LIQUID FORECAST WITH THE SYSTEM 
SUNDAY NIGHT THROUGH MONDAY. MOST OF THIS WILL BE SNOW AND SLEET 
ACROSS NE NJ...LOWER HUDSON VALLEY AND CT. 

ACROSS LI/NYC THERE IS A POTENTIAL FOR A PERIOD OF HEAVY
RAIN...WITH SOME MODELS SIGNALING UP TO 2 INCHES OF QPF.
ALTHOUGH THIS POTENTIAL IS LOW...IF MODEL TRENDS CONTINUE
NORTH...THIS POTENTIAL WOULD INCREASE...RESULTING IN URBAN
FLOODING ISSUES.

NO SIGNIFICANT WIDESPREAD PCPN IS FORECAST FOR THE REMAINDER OF THE 
PERIOD.

&&

.TIDES/COASTAL FLOODING...
THERE IS A LOW PROBABILITY OF MINOR COASTAL FLOODING THRESHOLDS
BEING REACHED WITH THE MONDAY MORNING HIGH TIDE CYCLE ALONG THE
WESTERN SOUTH SHORE BAYS AND WESTERN PORTIONS OF LI SOUND.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...WINTER STORM WATCH FROM SUNDAY EVENING THROUGH MONDAY 
     AFTERNOON FOR CTZ011-012.
     WINTER STORM WARNING FROM 7 PM SUNDAY TO 6 PM EST MONDAY FOR 
     CTZ005>010.
NY...WINTER STORM WATCH FROM SUNDAY EVENING THROUGH MONDAY 
     AFTERNOON FOR NYZ071>075-078>081-176>179.
     WINTER STORM WARNING FROM 7 PM SUNDAY TO 6 PM EST MONDAY FOR 
     NYZ067>070.
NJ...WINTER STORM WATCH FROM SUNDAY EVENING THROUGH MONDAY 
     AFTERNOON FOR NJZ004-006-104>108.
     WINTER STORM WARNING FROM 7 PM SUNDAY TO 6 PM EST MONDAY FOR 
     NJZ002-103.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST SUNDAY FOR ANZ338.
     SMALL CRAFT ADVISORY UNTIL 6 AM EST SUNDAY FOR ANZ350-353-355.

&&

$$
SYNOPSIS...NV/DW
NEAR TERM...JP/NV/DW
SHORT TERM...NV
LONG TERM...DW
AVIATION...MET
MARINE...JP/NV/DW
HYDROLOGY...NV/DW
TIDES/COASTAL FLOODING...









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