FXUS61 KOKX 220937 CCA
AFDOKX

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE NEW YORK NY
436 AM EST TUE DEC 22 2009

.SYNOPSIS...
CANADIAN HIGH PRESSURE BUILDS IN THROUGH THURSDAY NIGHT...THEN
SLOWLY RETREATS TO THE NORTHEAST INTO SATURDAY. A COMPLEX...POTENT
STORM SYSTEM WILL IMPACT THE REGION FROM LATE CHRISTMAS DAY
THROUGH SATURDAY NIGHT. HIGH PRESSURE THEN BUILDS IN FROM THE WEST
EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WITH SOME SNOW MELT TODAY...THEN REFREEZE TONIGHT...WILL RE-ISSUE
SPS FOR BLACK ICE THIS MORNING.

GUSTY NW WINDS CONTINUE TODAY DUE TO TIGHT PRESSURE GRADIENT
BETWEEN SLOWLY DEPARTING LOW OVER THE CANADIAN MARITIMES AND HIGH
PRESSURE OVER SOUTH CENTRAL CANADA. IT SHOULD AVERAGE OUT TO
MOSTLY SUNNY/SUNNY...THOUGH COULD SEE SOME STRATO-CU THIS MORNING
OVER WESTERN AREAS (EVIDENT ON SATELLITE APPROACHING FROM THE SW)
BEFORE THINGS MIX OUT THIS MORNING DUE TO STRENGTH OF DOWN-SLOPE
FLOW. FOR HIGHS BLENDED COLDER MET GUIDANCE WITH EVEN COLDER NAM
2-METER TEMPERATURES TO REFLECT IMPACT OF SNOW PACK (HIGHS AROUND
30-LOWER 30S - AROUND 10 DEGREES BELOW NORMAL).

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
CUTOFF LOW PASSING TO OUR NORTH/NORTHEAST TONIGHT/WEDNESDAY WILL
BRING SOME CLOUDS TO THE REGION...BUT DOWN-SLOPE FLOW AND DRY LOW
LEVELS SHOULD KEEP THINGS DRY (CANNOT COMPLETELY RULE OUT SOME
FLURRIES WITH ITS PASSAGE..ESPECIALLY ACROSS NORTHERN ZONES...BUT
NOT CONFIDENT ENOUGH TO PUT IN GRIDS/ZONES FOR NOW). USED BLEND
COLDER MAV/EVEN COLDER NAM 2-METER TEMPERATURES FOR LOWS TONIGHT
AND BLEND MAV/MET/COLDER NAM 2-METER TEMPERATURES FOR HIGHS
WEDNESDAY TO REFLECT IMPACT OF SNOW COVER (LOWS MAINLY IN THE
TEENS TONIGHT (AROUND 20 NYC METRO) AND HIGHS WEDNESDAY UPPER 20S
TO LOWER 30S - BOTH AROUND 10 DEGREES BELOW NORMAL).

ON AVERAGE PARTLY CLOUDY WEDNESDAY NIGHT-THURSDAY NIGHT (DUE TO
DEPARTING CUTOFF/COLD ADVECTION/THEN MOISTURE AHEAD OF STORM
SYSTEM APPROACHING FROM THE WEST WEDNESDAY NIGHT/THURSDAY/THURSDAY
NIGHT RESPECTIVELY). 

FOR TEMPERATURES BLENDED COLDER MET WITH NAM 2-METER TEMPERATURES
WEDNESDAY NIGHT/THURSDAY AND MEX/MEX ENSEMBLE MEAN/LOW MEX
ENSEMBLE MEAN MEMBER WITH NAM 2-METER TEMPERATURE FOR HIGHS
THURSDAY (ALL TO REFLECT IMPACT OF SNOW COVER). LOWS WEDNESDAY
NIGHT MAINLY TEENS-LOWER 20S...HIGHS THURSDAY MID 30S (BOTH BELOW
NORMAL)...AND LOWS THURSDAY NIGHT MAINLY IN THE 20S (AROUND 30 NYC
METRO) - FINALLY A PERIOD WITH NEAR NORMAL TEMPERATURES.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
ALL GUIDANCE HAS SLOWED DOWN ARRIVAL OF PRECIPITATION AHEAD OF
COMPLEX STORM SYSTEM APPROACHING FROM THE PLAINS. ECMWF IS EVEN
SLOWER THAN GFS AND CMC GLOBAL (AND LINGERS PRECIPITATION LONGER
THAN EITHER OF THE TWO MODELS). FOR NOW HAVE USED GFS/CMC-GLOBAL
BLEND FOR THE EXTENDED AS IT OFFERS THE LEAST DEPARTURE FROM
CONTINUITY (ALSO ECMWF LOOKS A LITTLE FUNNY IN HOW IT BARELY
MOVES THE SURFACE LOW FROM SATURDAY NIGHT TO SUNDAY MORNING).

IN TERMS OF SENSIBLE WEATHER...WINTRY MIX ARRIVES FRIDAY
AFTERNOON/EVENING AND TRANSITIONS TO PRIMARILY FREEZING RAIN
ACROSS THE NORTHERN INTERIOR AND MAINLY RAIN FOR LONG ISLAND/NYC
METRO/COASTAL CT FRIDAY NIGHT (COULD SEE SOME SLEET/SNOW MIXED IN
AS WELL BUT THESE SHOULD NOT BE THE PREDOMINATE P-TYPE ESPECIALLY
ACROSS NYC/LONG ISLAND). HAVE RISING TEMPERATURES FRIDAY NIGHT FROM A
MID- EVENING LOW IN RESPONSE TO STRONG LOW LEVEL WARM ADVECTION
(JUST RISE TEMPERATURES LESS ACROSS NORTHERN INTERIOR DUE TO
STRONG DAMMING SIGNATURE). PRECIPITATION SHOULD CHANGE TO ALL RAIN
ACROSS THE ENTIRE CWA BY SATURDAY AFTERNOON. AS STORM SYSTEM
EXITS...ENOUGH COLDER AIR FILTERS IN BEHIND IT THAT PRECIP COULD
END AS A PERIOD OF SNOW SHOWERS ACROSS THE INTERIOR SATURDAY NIGHT.

WILL ADVERTISE POTENTIAL FOR A SIGNIFICANT FREEZING RAIN ACROSS
THE INTERIOR IN THE HWO LATE FRIDAY INTO SATURDAY MORNING. GIVEN
UNCERTAINTY IN TIMING...THERE IS STILL SOME UNCERTAINTY WITH THE
EXACT OUTCOME WITH THIS SYSTEM. THOUGH IT DOES APPEAR CLEAR THAT A
COASTAL LOW WILL FORM AHEAD OF THE MAIN LOW TRACKING INTO THE SAINT
LAWRENCE RIVER VALLEY...WITH A DAMMING HIGH AND DECENT SNOW PACK
PRECEDING IT...SO THERE IS A REASONABLE EXPECTATION OF A FREEZING
RAIN EVENT ACROSS THE INTERIOR...MAIN QUESTION IS TIMING.

FOR NOW PLAYING SUNDAY DRY...AS WELL AS SUNDAY NIGHT AND MONDAY
(ECMWF ALSO AGREES WITH LATTER TWO PERIODS BEING DRY AS WELL).

FOR TEMPERATURES BLENDED MEX/MEX ENSEMBLE MEAN/LOW MEX ENSEMBLE
MEMBER TO ACCOUNT FOR SNOW BACK AND GFS SURFACE WARM BIAS WHEN
DEALING WITH A DAMMING HIGH THROUGH SATURDAY NIGHT...THEN A
MEX/MEX ENSEMBLE MEAN BLEND SUNDAY-MONDAY WITH NEAR NORMAL
TEMPERATURES. 

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
VFR THROUGH THE TAF PERIOD. 

HIGH CONFIDENCE FORECAST WITH WINDS 290-320 DEGREES AND SUSTAINED
SPEEDS 10-15KTS THROUGH THE AFTERNOON. WIND GUSTS WILL REMAIN IN
THE 20-25KT RANGE.

ANY SLUSH OR WATER ON TAXIWAYS WILL REFREEZE OVERNIGHT.

OUTLOOK 00Z WEDNESDAY THROUGH SATURDAY... 
TUE NIGHT-THU...VFR. GUSTY NW WINDS THROUGH WED AFTERNOON. 
FRI...VFR...WITH SUB-VFR POSSIBLE LATE.
FRI NGT - SAT...SUB VFR WITH A WINTRY MIX CHANGING TO RAIN FM L.I 
NNW TO ORANGE COUNTY SAT AFTN.  GUSTY SE-S WINDS AND LLWS POSSIBLE. 

&&

.MARINE...
WIND GUSTS ON THE OCEAN HAVE FALLEN JUST BELOW GALE. ALTHOUGH A FEW 
GALE GUSTS ARE STILL POSSIBLE THROUGH SUNRISE...DO NOT FEEL A GALE 
WARNING IS NEEDED...SO WILL GO STRAIGHT TO A SMALL CRAFT ADVISORY ON 
THE OCEAN WATERS.

SCA WILL BE UP FOR ALL WATERS THROUGH AT LEAST TONIGHT FOR WIND 
GUSTS OVER 25 KT...AND WILL REMAIN UP ON THE OCEAN THROUGH WED AS 
WINDS WILL CONTINUE TO GUST OVER 25 KT ALONG WITH SEAS GREATER THAN 
5 FT.

SCA CONDITIONS EXPECTED...ESPECIALLY ON THE OCEAN WATERS...THROUGH 
THE END OF THE WEEK. THE NEXT STORM SYSTEM WILL IMPACT THE REGION 
LATE IN THE WEEK AND THROUGH THE WEEKEND WITH SCA CONDITIONS AND 
POSSIBLE GALES ON THE OCEAN WATERS.

&&

.HYDROLOGY...
SLOW MELT OF SNOW PACK EXPECTED THROUGH THURSDAY NIGHT...WITH
LITTLE HYDROLOGIC IMPACT EXPECTED.

THERE IS THE POTENTIAL FOR 1-2 INCHES OF LIQUID EQUIVALENT LATE
FRIDAY INTO SATURDAY NIGHT...FALLING ON TOP OF A SNOW PACK
ESTIMATED TO CONTAIN AROUND 1-2 INCHES OF WATER EQUIVALENT
(DEPENDING ON SNOW DEPTH - EVEN LESS ACROSS NW ZONES WERE LESS
THAN 10 INCHES OF SNOW FELL). THIS COULD LEAD TO FLOODING ACROSS
THE REGION (BOTH URBAN AND OF RIVERS) DEPENDING ON HOW RAPID THE
SNOW MELT OCCURS AND OVER WHAT DURATION THE HEAVY RAIN FALLS.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST WEDNESDAY FOR ANZ330-335-
     338-340-345.
     SMALL CRAFT ADVISORY UNTIL 6 PM EST WEDNESDAY FOR ANZ350-353-
     355.

&&

$$

PUBLIC/HYDROLOGY...MALOIT
AVIATION...98
MARINE...MPS