FXUS61 KOKX 221742
AFDOKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
1242 PM 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 /THIS AFTERNOON/...
GUSTY NW WINDS CONTINUE 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.
&&
.SHORT TERM /TONIGHT THROUGH WEDNESDAY 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 /THURSDAY 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 /18Z TUESDAY THROUGH SUNDAY/...
STRONG PRESSURE GRADIENT REMAINS IN PLACE YIELDING GUSTY NORTHWEST
WINDS THIS AFTERNOON. WEAK SURFACE TROF PUSHES THROUGH OVER THE
NEXT COUPLE OF HOURS. HIGH PRESSURE BUILDS IN THEREAFTER.
FOR ALL TERMINALS...WINDS MAY BE 10 TO 20 DEGREES LEFT OF FORECAST
FROM NOW THROUGH 19-20Z.
TAF COMMENTS (FORECASTER INSIGHT ON TIMING, CONFIDENCE, TRENDS AND GROUND OPS)
KEWR...FORECAST ON TRACK...NO UNSCHEDULED AMENDMENTS
ANTICIPATED
KEWR HOURLY WIND FORECAST
ALL WIND DIRECTIONS ARE TRUE...ADD 13 DEGREES FOR MAGNETIC
22/17Z 28015G22KT
22/18Z 29014G21KT
22/19Z 29013G21KT
22/20Z 30013G20KT
22/21Z 30011KT
22/22Z 30011KT
22/23Z 30010KT
23/00Z 30010KT
23/01Z 30009KT
23/02Z 30009KT
23/03Z 30008KT
KJFK...FORECAST ON TRACK...NO UNSCHEDULED AMENDMENTS
ANTICIPATED
KLGA...FORECAST ON TRACK...NO UNSCHEDULED AMENDMENTS
ANTICIPATED
KTEB...FORECAST ON TRACK...NO UNSCHEDULED AMENDMENTS
ANTICIPATED
KHPN...FORECAST ON TRACK...NO UNSCHEDULED AMENDMENTS
ANTICIPATED
KSWF...FORECAST ON TRACK...NO UNSCHEDULED AMENDMENTS
ANTICIPATED
KISP...FORECAST ON TRACK...NO UNSCHEDULED AMENDMENTS
ANTICIPATED
KBDR...FORECAST ON TRACK...NO UNSCHEDULED AMENDMENTS
ANTICIPATED
KGON...FORECAST ON TRACK...NO UNSCHEDULED AMENDMENTS
ANTICIPATED
OUTLOOK 00Z WEDNESDAY THROUGH SATURDAY...
TUE NIGHT-THU...VFR. GUSTY NW WINDS MAINLY WED AFTERNOON.
FRI...VFR...WITH CHANCE OF SUB-VFR LATE.
FRI NGT - SAT...SUB VFR WITH A WINTRY MIX CHANGING TO RAIN NORTH OF
CITY. PROBABLY PLAIN RAIN FOR EWR/LGA/JFK/ISP. GUSTY SE-S WINDS AND
LLWS POSSIBLE.
&&
.MARINE...
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.
&&
$$
AVIATION...JC
