FXUS61 KOKX 222134
AFDOKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
434 PM EST TUE DEC 22 2009

.SYNOPSIS...
AN UPPER LEVEL LOW WILL PASS TO THE NORTH TONIGHT INTO WEDNESDAY.
A HIGH PRESSURE RIDGE BUILDING SOUTHEAST FROM CANADA WILL THEN
FOLLOW FOR WEDNESDAY NIGHT INTO THURSDAY NIGHT. ONSHORE FLOW AHEAD
OF AN APPROACHING FRONTAL SYSTEM COULD BRING SOME SPOTTY LIGHT
PRECIPITATION ON FRIDAY...WITH STEADIER PRECIPITATION LIKELY FROM
CHRISTMAS NIGHT INTO SUNDAY MORNING. HIGH PRESSURE WILL THEN
BUILD FROM THE WEST EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AFTER SOME BROKEN HIGH/MID LEVEL CLOUDS MOVE OFF TO THE EAST... 
SKIES SHOULD CLEAR TONIGHT AS A SFC TROUGH MOVES THROUGH. 
NW WINDS ARE STILL GUSTY ATTM...BUT IT IS POSSIBLE THAT THE SFC
LAYER COULD DECOUPLE ENOUGH LATE TONIGHT ACROSS THE INTERIOR AND
LONG ISLAND PINE BARRENS REGION TO ALLOW FOR BRIEF ENHANCED
RADIATIONAL COOLING AND TEMPS DROPPING TO NEAR 10 ABOVE. 
LOWS ELSEWHERE SHOULD BE IN THE LOWER 20S NYC...AND 15-20 MOST
ELSEWHERE ALONG THE COAST. 

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
CLOUDS SHOULD INCREASE WED MORNING/AFTERNOON AS AN UPPER LOW
PASSING JUST TO THE NORTH CAPTURES MOISTURE AHEAD OF A WARM
FRONT RETROGRADING SW INTO THE CANADIAN MARITIMES. 
POSITIVE 500-800 MB DIFFERENTIAL CYCLONIC VORTICITY ADVECTION ON
THE SOUTHERN FLANK OF THE UPPER LOW PER BOTH NAM/GFS SUPPORTS IDEA
OF ENOUGH LIFT TO GENERATE SOME FLURRIES IN SOUTHERN CT AND
PARTS OF THE LOWER HUDSON VALLEY. ONE LAST SURGE OF COLD AIR WILL
FOLLOW PASSAGE OF THE UPPER LOW...WITH GUSTY NW FLOW CONTINUING
AND TEMPS NEARLY AS COLD AS THOSE FORECAST FOR TONIGHT. 

SUNNY DAY ON TAP FOR THU AS HIGH PRESSURE RIDGING DOWN FROM
ONTARIO BUILDS INTO THE AREA. SOME MODERATION IN TEMPS EXPECTED AS
MID LEVEL HEIGHTS RISE IN THE WAKE OF THE DEPARTING CLOSED
LOW...WITH HIGHS IN THE MID 30S TO NEAR 40. 

THE AXIS OF THE HIGH MOVES EAST OF THE AREA THU NIGHT...WITH LOW
LEVEL MOISTURE QUICKLY RETURNING LATE THU NIGHT INTO FRI WELL
AHEAD OF AN APPROACHING FRONTAL SYSTEM. THIS MOISTURE COULD RESULT
IN FOG IN PLACES LATE THU NIGHT INTO FRI MORNING...WHICH COULD
CAUSE RIMING AND VERY SLIPPERY CONDITIONS CHRISTMAS MORNING...AND
ALSO INCREASING LOW CLOUDS. STEADIER PRECIP WITH THE SYNOPTIC
SCALE SYSTEM OFF TO THE WEST WILL LIKELY HOLD OFF UNTIL FRI
NIGHT...BUT WITH THE ABUNDANT LOW LEVEL MOISTURE AND WEAK LIFT
THERE COULD BE SOME LIGHT RAIN OR DRIZZLE IN THE AFTERNOON. 
WILL HAVE TO WATCH TEMPS OVER THE INTERIOR...WHICH VIA CLOUD COVER
AND COLD AIR DAMMING WILL BE AT OR BARELY ABOVE FREEZING...AND
SUPPORTIVE OF LIGHT FREEZING RAIN/DRIZZLE ON COLDER SURFACES. 

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
A HIGHLY AMPLIFIED UPPER AIR PATTERN WILL BE FEATURED AT THE ONSET
OF THE PERIOD WITH A LARGE CLOSED LOW OVER THE UPPER MIDWEST AND A
RIDGE ALONG THE EASTERN SEABOARD. THIS BLOCKING PATTERN WILL ALLOW
FOR SLOW PROGRESSION OF A FRONTAL SYSTEM ACROSS THE EASTERN
SEABOARD FRIDAY NIGHT INTO SUNDAY. THE GLOBAL MODELS HAVE SOME
TIMING ISSUES...BUT OVERALL ARE IN GOOD AGREEMENT WITH THE MASS
FIELDS. THE 12Z ECMWF CONTINUES TO BE A SHADE SLOWER WITH THE
FRONT AND BASED ON THIS PATTERN...SLOWER SEEMS TO BE PRUDENT. 

A 1040 MB HIGH BUILDS ACROSS EASTERN CANADA FRI INTO SAT WITH SOME
FREEZING RAIN LIKELY ACROSS INTERIOR VALLEYS. THE EXTENT OF THE
COLD AIR DAMMING WILL BE BEST EVALUATED AS WE GET CLOSER TO THE
EVENT. VERTICAL TEMP PROFILE THOUGH DO NOT SUPPORT FROZEN PCPN
(SNOW OR SLEET). THE COLD FRONT ALONG WITH A SFC WAVE OVER THE MID
ATLANTIC WILL BRING RAINS TO THE AREA SAT AFTERNOON AND
NIGHT...WITH CONDITIONS DRYING OUT ON SUNDAY BEHIND THE FRONT.
SIGNIFICANT RAINFALL ON TOP OF THE SNOW PACK WILL LIKELY LEAD TO
SOME FLOODING ISSUES...ESPECIALLY ACROSS CENTRAL AND EASTERN 
LONG ISLAND. 

A STRONG NW FLOW WILL DEVELOP MON AND TUE...WITH TEMPERATURES 
DROPPING BACK INTO THE 30S FOR HIGHS. 

&&

.AVIATION /21Z 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 SUNDAY... 
TUE NIGHT-THU...VFR. GUSTY NW WINDS MAINLY WED AFTERNOON. SUB-VFR
WITH LOW CLOUDS AND/OR FOG POSSIBLE LATE AT NIGHT. 

FRI...SUB-VFR POSSIBLE WITH LOW CLOUDS AND/OR FOG. LIGHT FREEZING
RAIN OR FREEZING DRIZZLE ALSO POSSIBLE INLAND (KHPN/KSWF). 

FRI NIGHT-SAT...SUB VFR...WITH FREEZING RAIN POSSIBLE INTO SAT
MORNING FOR KSWF...OTHERWISE RAIN. GUSTY SE-S WINDS AND LLWS 
ALSO POSSIBLE. 

SUNDAY...RAIN TAPERING OFF FROM W-E DURING THE DAY...WITH
CONDITIONS GRADUALLY IMPROVING TO VFR IN THE AFTERNOON/NIGHT.

&&

.MARINE...
SCA REMAINS IN EFFECT FOR ALL WATERS ATTM...WITH GUSTS 25-30 KT.
WINDS SHOULD DECREASE ENOUGH OVERNIGHT OVER THE HARBOR AND
WESTERN SOUND...WITH ENOUGH TIME BETWEEN THEN AND POSSIBLE RETURN
OF SCA CONDITIONS DURING WED AFTERNOON...TO WARRANT DROPPING SCA
BEFORE MIDNIGHT TONIGHT. 

SCA CONDITIONS ARE LIKELY WED NIGHT/THU MORNING VIA ONE LAST CAA
SURGE FOLLOWING PASSAGE OF AN UPPER LOW TO THE NORTH. THE NEXT
STORM SYSTEM WILL THEN IMPACT THE REGION LATE IN THE WEEK AND
THROUGH THE WEEKEND...WITH SCA CONDITIONS ON THE OCEAN WATERS.
MARGINAL SCA CONDITIONS MON-TUE WITH THE NW FLOW BEHIND THE
DEPARTING SYSTEM. UNDERCUT WAVEWATCH BY 1-2 FT ON THE OCEAN WATERS
DURING THIS TIME BASED ON FORECAST WIND SPEEDS.

&&

.HYDROLOGY...
SOME MELTING OF SNOW PACK POSSIBLE THU-FRI AS TEMPS RISE TO NEAR
40 IN NYC METRO AND COASTAL SECTIONS. 

POTENTIAL EXISTS FOR ABOUT AN INCH LIQUID EQUIVALENT QPF MAINLY
FRI NIGHT INTO SUN MORNING...ON TOP OF SNOW PACK WITH ABOUT 1-2
INCHES WATER EQUIVALENT IN MOST PLACES...LESSER NORTH/WEST OF
NYC. THIS COULD LEAD TO BOTH URBAN AND SMALL RIVER/STREAM
FLOODING...DEPENDING ON SPEED OF SNOW MELT AND DURATION OF 
HEAVIER RAIN. 

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR ANZ335-
     338-345.
     SMALL CRAFT ADVISORY UNTIL 6 PM EST WEDNESDAY FOR ANZ330-340.
     SMALL CRAFT ADVISORY UNTIL 6 AM EST THURSDAY FOR ANZ350-353-
     355.

&&

$$

SYNOPSIS/NEAR TERM/SHORT TERM...BG 
LONG TERM...DW 
AVIATION...JC
MARINE/HYDROLOGY...BG/DW