441  
FXUS61 KOKX 111240  
AFDOKX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NEW YORK NY  
740 AM EST SUN DEC 11 2016  
   
SYNOPSIS
 
 
HIGH PRESSURE MOVES ACROSS INTO THIS MORNING, SLIDING OFFSHORE THIS  
AFTERNOON. LOW PRESSURE WELL TO THE WEST MOVES INTO THE GREAT LAKES  
WITH AN ASSOCIATED WARM FRONT APPROACHING THE REGION. THE WARM FRONT  
MOVES ACROSS THE REGION LATE SUNDAY NIGHT. A COLD FRONT FOLLOWS FOR  
MONDAY AFTERNOON. HIGH PRESSURE THEN BUILDS TO THE SOUTHWEST OF THE  
REGION MONDAY NIGHT THROUGH MIDWEEK. FOR MIDWEEK, THERE WILL BE A  
WEAK LOW MOVING TO WELL NORTH OF THE REGION AND ANOTHER WEAK LOW  
WELL OFFSHORE. AN ARCTIC COLD FRONT THEN FOLLOWS THURSDAY.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
FORECAST ON TRACK SO FAR THIS MORNING WITH ONLY MINOR ADJUSTMENTS  
TO TEMPERATURES AND DEWPOINTS TO BETTER MATCH OBSERVED TRENDS.  
 
HIGH PRESSURE TRAVERSES THE REGION AND MOVES OFFSHORE. RIDGING  
ALOFT WITH JET STREAM LIFTING FARTHER NORTH. AMBIENT COLD AIRMASS  
WILL HAVE LITTLE VERTICAL MIXING TODAY WITH A LACK OF PRESSURE  
GRADIENT. LOW TO MID 30S FOR HIGHS AGAIN. DRY INITIALLY, BUT  
CHANCES FOR SNOW RAPIDLY INCREASE IN AFTERNOON WITH ISENTROPIC  
LIFT AND MOISTENING ATMOSPHERIC COLUMN. EXPECTING A COATING OF  
SNOW IN ACCUMULATION ESPECIALLY IN AREAS AT OR BELOW FREEZING.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/
 
 
MOIST BOUNDARY LAYER LAYER LOSES MOISTURE IN THE MID LEVELS LATER  
IN THE EVENING. CHANCES LOWER THEREFORE FROM SOUTH TO NORTH FOR  
SNOW BEFORE MORE SYNOPTIC LIFT IN THE RIGHT REAR QUAD OF THE  
UPPER LEVEL JET ARRIVES OVERNIGHT. THIS ALONG WITH POSITIVE  
VORTICITY ADVECTION AHEAD OF AMPLIFYING UPPER LEVEL TROUGH WILL  
INCREASE THE LIFT. WIDESPREAD PRECIPITATION EXPECTED ACROSS THE  
REGION OVERNIGHT THROUGH MONDAY MORNING. INITIALLY THIS WILL BE  
SNOW, BUT WITH WARMTH ARRIVING WITHIN FIRST FEW THOUSAND FEET  
ABOVE SURFACE BEHIND WARM FRONT, TEMPERATURES IN THE LAYER RISE  
ABOVE FREEZING. FOR THE MOST INTERIOR VALLEYS, THERE WILL BE A MIX  
OF SNOW AND SLEET AS WELL AS FREEZING RAIN WHILE CLOSER TO THE  
COAST, SNOW WILL MIX WITH RAIN.  
 
THE UNCERTAINTY HERE IS A MATTER OF TIMING OF THE WARM FRONT AND  
WARM AIR ADVECTION ALOFT AND PRECIPITATION. UTILIZING MULTIPLE  
MODELS WITH DIFFERENT LOW LEVEL THICKNESSES RESTRICTS ANY FREEZING  
RAIN TO THE FAR INTERIOR PORTIONS OF THE REGION WHERE SURFACE  
TEMPERATURES WILL BE AT OR BELOW FREEZING WHEN THE TEMPERATURES  
WITHIN A FEW THOUSAND FEET ABOVE RISE 1-3 DEGREES ABOVE FREEZING.  
THESE LOCATIONS INCLUDE ORANGE, PUTNAM, AND WESTERN PASSAIC WHERE  
A COMBINATION OF 2 TO 5 INCHES OF SNOW AND A LIGHT ICE  
ACCUMULATION OF LESS THAN A TENTH OF AN INCH IS EXPECTED. HENCE,  
THIS IS WHERE THERE IS A WINTER WEATHER ADVISORY IN EFFECT.  
 
HOWEVER, IF TEMPERATURES AT THE SURFACE CLOSER TOWARDS THE COAST,  
SUCH AS ROCKLAND, WESTCHESTER, EASTERN PASSAIC, WESTERN ESSEX,  
WESTERN UNION, TREND JUST A FEW DEGREES COLDER FOR OVERNIGHT, THE  
WINTRY MIX WOULD INCLUDE FREEZING RAIN WITH A POSSIBILITY OF THE  
WINTER WEATHER ADVISORY GETTING EXPANDED. HOWEVER, RECENT MODEL  
RUNS, SUCH AS THE NAM12 CONTINUE TO SHOW TEMPERATURES AND EVEN WET  
BULB TEMPERATURES A FEW DEGREES ABOVE FREEZING FOR THE  
PRECIPITATION OVERNIGHT INTO MONDAY MORNING. SO, CONFIDENCE OF ANY  
ICE ACCUMULATION IS LOWER BECAUSE OF THIS BUT A CHANCE OF FREEZING  
RAIN IS IN THE FORECAST.  
 
ALL RAIN WITH WARM FRONT LIFTING THROUGH MONDAY MORNING WITH LAST  
PLACES TO GET ABOVE FREEZING BEING NORTHERN PARTS OF THE LOWER  
HUDSON VALLEY.  
 
IN TERMS OF WINDS, THEY INCREASE MONDAY MORNING INTO THE  
AFTERNOON, ESPECIALLY ALONG THE COAST WITH A S-SW FLOW OF 10 TO 20  
MPH WITH GUSTS UP TO 30 MPH. HIGHER GUSTS WILL BE POSSIBLE WITHIN  
ANY MODERATE TO LOCALLY HEAVY RAIN WITH THE PASSAGE OF THE LOW  
LEVEL JET.  
 
THE RAIN TAPERS OFF MONDAY AFTERNOON INTO MONDAY NIGHT AFTER THE  
PASSAGE OF A COLD FRONT. WESTERLY FLOW WILL ADVECT IN DRIER AIR  
ALLOWING FOR A GRADUAL DECREASE IN CLOUDS.  
 

 
   
LONG TERM /TUESDAY THROUGH SATURDAY/
 
 
UPPER AIR PATTERN WILL FEATURE AN ANOMALOUSLY HIGH AMPLITUDE RIDGE  
OVER ALASKA, WHICH WILL ALLOW THE POLAR VORTEX TO DROP SOUTHWARD  
INTO CENTRAL AND EASTERN CANADA BY MIDWEEK. THIS WILL OPEN THE DOOR  
FOR THE COLDEST AIRMASS OF THE SEASON FOR THE SECOND HALF OF THE  
WEEK.  
 
HIGH PRESSURE BRIEFLY FOLLOWS FOR TUESDAY WITH TEMPERATURES NEAR  
SEASONABLE LEVELS. ANOTHER PIECE OF PACIFIC SHORTWAVE ENERGY RACES  
ACROSS THE COUNTRY. GLOBAL MODELS VARY WITH THE AMPLITUDE OF THIS  
FEATURE WITH THE NEARLY ZONAL FLOW IN THE SOUTHERN BRANCH OF THE  
POLAR JET. THE AMOUNT OF PHASING WITH THE NORTHERN BRANCH LOOKS TO  
BE THE DIFFERENCE AND 12Z MODELS HAVE SHIFTED TOWARDS A LESS  
PHASED PATTERN WITH THE ENERGY PASSING WELL SOUTH OF THE AREA.  
HAVE DECREASED POPS TO SCHC BASED ON THIS TREND. HOWEVER...DUE TO  
THE FAST FLOW, THERE IS LIKELY TO BE UNCERTAINTY IN THE MAGNITUDE  
OF THIS SYSTEM THE NEXT SEVERAL DAYS. ARCTIC AIR THEN SPILLS  
SOUTHWARD ON THE BACKSIDE OF THE SYSTEM THURSDAY INTO FRIDAY WITH  
DAYTIME HIGHS POSSIBLY NOT GETTING ABOVE FREEZING WITH OVERNIGHT  
LOWS IN THE SINGLE DIGITS TO TEENS. THESE VALUES ARE 15 TO 20  
DEGREES BELOW NORMAL. TO MAKE MATTERS WORSE, STRONG NW WINDS WILL  
FOLLOW FOR THURSDAY PRODUCING VERY COLD WIND CHILL VALUES.  
 
MEANWHILE...AN UPPER LEVEL TROUGH MOVES ONSHORE FROM THE PACIFIC  
DURING THE SECOND HALF OF THE WEEK. THERE ARE SOME DIFFERENCES  
ALOFT BY SAT...ALTHOUGH CONFLUENT FLOW ACROSS THE COUNTRY AND  
DEVELOPING LOW PRES IN THE PLAINS COULD BRING PCPN BACK TO THE  
REGION DURING SAT. THE COLD AIRMASS ALREADY IN PLACE SHOULD ALL  
FOR PCPN TO START IN THE FROZEN PHASE BUT WILL LIKELY  
MIX/CHANGEOVER WITH SLY FLOW.  
 

 
   
AVIATION /12Z SUNDAY THROUGH THURSDAY/
 
 
***HIGH IMPACT WEATHER LIKELY LATE TONIGHT INTO MONDAY MORNING***  
 
HIGH PRESSURE WILL MOVE OFFSHORE TODAY. A LOW PRESSURE SYSTEM  
WILL APPROACH TONIGHT.  
 
LIGHT MAINLY WNW FLOW WITH BROKEN HIGH AND MID LEVEL CLOUDS EARLY  
THIS MORNING TO START. WINDS WILL BACK SW-S THIS AFTERNOON AND  
INCREASE CLOSE TO 10KT AS CLOUDS LOWER/THICKEN, THEN LIGHT SNOW  
LIKELY TO DEVELOP LATE THIS AFTERNOON INTO EARLY THIS EVENING, AND  
CIGS LOWERING TO MVFR, POSSIBLY IFR FOR A TIME AT KSWF.  
 
A BRIEF BREAK IN PRECIP AND A RETURN TO VFR CONDITIONS IS  
POSSIBLE LATE THIS EVENING, MAINLY AROUND NYC METRO. AS STEADIER  
PRECIP RESUMES AFTER MIDNIGHT, PRECIP SHOULD GRADUALLY CHANGE TO  
RAIN, WITH IFR CONDITIONS DEVELOPING. KSWF SHOULD REMAIN ALL SNOW  
THROUGH THE NIGHT.  
 
S WINDS G20KT LATE AT KISP AND POSSIBLY KJFK/KGON.  
 
HERE ARE THE MOST LIKELY SNOWFALL ACCUMULATIONS:  
 
KSWF: AROUND 4 INCHES.  
KHPN/KBDR/KGON/KTEB: UP TO AN INCH.  
KISP/KJFK/KLGA/KEWR: ONLY A COATING OF ACCUMULATION.  
   
OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY
 
 
   
MONDAY
 
IFR CONDITIONS TO START, BECOMING MVFR BY MIDDAY AT  
KSWF, THEN IMPROVING TO VFR DURING THE AFTERNOON THROUGHOUT.  
SNOW CHANGING TO RAIN EARLY AT KSWF, AND RAIN ELSEWHERE, WITH  
PRECIP TAPERING OFF IN THE AFTERNOON.  
 
LLWS POSSIBLE IN THE MORNING NYC METROS/COAST. S/SW WINDS G25-30KT  
IN THE MORNING AT THE NYC METROS AND KISP, BECOMING W IN THE  
AFTERNOON. CHANCE FOR G40KT AT KISP AND POSSIBLY KJFK IN HEAVIER  
RAIN IN THE MORNING.  
   
MONDAY NIGHT-TUESDAY
 
VFR.  
   
WEDNESDAY
 
SLIGHT CHANCE OF MVFR CONDITIONS WITH ANY SNOW OR RAIN  
SHOWERS. NW WINDS G25-30KT AFTER MIDNIGHT.  
   
THURSDAY
 
VFR. NW WINDS G30KT.  
 

 
   
MARINE
 
 
AS LOW PRESSURE APPROACHES TONIGHT, S-SW WINDS WILL INCREASE, AND  
GUSTS TO 35-40 KT ARE EXPECTED ON THE OCEAN WATERS AND ON THE LONG  
ISLAND SOUTH SHORE BAYS, SO GALE WARNINGS HAVE BEEN ISSUED FOR LATE  
TONIGHT INTO MONDAY FOR THOSE WATERS. SCA ALSO ISSUED FOR THE  
REMAINING WATERS THROUGH AT LEAST MONDAY MAINLY FOR POST-FRONTAL WSW  
TO W FLOW GUSTING TO 25-30 KT. EASTERN LONG ISLAND SOUND MAY SEE A  
FEW GUSTS UP TO 35 KT IN THE AFTERNOON.  
 
SCA CONDITIONS WILL CONTINUE ON THE OCEAN AND THE EASTERN SOUND/BAYS  
THROUGH MONDAY NIGHT, AND OCEAN SEAS E OF FIRE ISLAND INLET MAY NOT  
SUBSIDE BELOW 5 FT TIL TUE AFTERNOON OR EVENING.  
 
AFTER AN ARCTIC COLD FRONTAL PASSAGE, SCA CONDITIONS SHOULD DEVELOP  
ON THE OCEAN WED NIGHT, AND ON ALL WATERS ON THU. GALE FORCE GUSTS  
MAY BE POSSIBLE ON THE OCEAN ON THU.  
 

 
   
HYDROLOGY
 
 
A HALF TO THREE QUARTERS OF AN INCH OF LIQUID EQUIVALENT PRECIPITATION  
IS FORECAST LATE TONIGHT THROUGH MONDAY. NO SIGNIFICANT PCPN  
(GREATER THAN 1/2 INCH) IS THEN EXPECTED THROUGH THE END OF THE  
WORK WEEK.  
 

 
   
TIDES/COASTAL FLOODING
 
 
WATER LEVELS COULD TOUCH MINOR FLOOD THRESHOLDS IN SOME SPOTS  
ALONG THE SW CT COASTLINE AND THE WESTERN BACK BAYS OF LONG ISLAND  
DURING THE MONDAY MORNING HIGH TIDE CYCLE. DEPARTURES OF ONLY LESS  
THAN 1 FT ABOVE ASTRONOMICAL HIGH TIDE ARE ALL THAT IS NEEDED TO  
REACH THESE THRESHOLDS, WHICH ARE POSSIBLE GIVEN HIGH ASTRONOMICAL  
HIGH TIDES AND MODERATE TO STRONG SE-S FLOW.  
 

 
   
EQUIPMENT
 
 
NEW YORK CITY NOAA WEATHER RADIO NWR TRANSMITTER KWO-35 MAY STILL  
BE EXPERIENCING INTERMITTENT OUTAGES.  
 

 
   
OKX WATCHES/WARNINGS/ADVISORIES
 
 
CT...NONE.  
NY...WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 10 AM EST  
MONDAY FOR NYZ067-068.  
NJ...WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 10 AM EST  
MONDAY FOR NJZ002.  
MARINE...SMALL CRAFT ADVISORY FROM 3 AM TO 6 PM EST MONDAY FOR ANZ335-  
338.  
SMALL CRAFT ADVISORY FROM 3 AM MONDAY TO 6 AM EST TUESDAY FOR  
ANZ330-340.  
GALE WARNING FROM 3 AM TO 6 PM EST MONDAY FOR ANZ353.  
GALE WARNING FROM 3 AM TO 1 PM EST MONDAY FOR ANZ355.  
GALE WARNING FROM 6 AM TO 1 PM EST MONDAY FOR ANZ345.  
GALE WARNING FROM 6 AM TO 6 PM EST MONDAY FOR ANZ350.  
 

 
 

 
SYNOPSIS...24/JM  
NEAR TERM...JM  
SHORT TERM...JM  
LONG TERM...24  
AVIATION...GOODMAN  
MARINE...GOODMAN/24  
HYDROLOGY...24/JM  
TIDES/COASTAL FLOODING...  
EQUIPMENT...  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab NY Page
The Nexlab NJ Page
The Nexlab CT Page Main Text Page