FXUS61 KOKX 240540
AFDOKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
1240 AM EST THU DEC 24 2009
.SYNOPSIS...
HIGH PRESSURE WILL BUILD SOUTHEAST FROM ONTARIO THROUGH THURSDAY.
THE HIGH WILL SHIFT EAST ON CHRISTMAS DAY...ALLOWING A FRONTAL
SYSTEM TO APPROACH FROM THE WEST. THIS FRONTAL SYSTEM...COMBINED
WITH COLD AIR LOCKED IN PLACE EAST OF THE APPALACHIANS...COULD
CREATE ICY CONDITIONS FOR INTERIOR SECTIONS CHRISTMAS NIGHT INTO
SATURDAY MORNING...AND HEAVY RAIN THROUGHOUT THE TRI-STATE AREA ON
SATURDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
CLEARING SKIES THIS EVENING. LOWS TONIGHT SHOULD BE IN THE 20S
NYC/IMMEDIATE COASTAL SECTIONS...AND TEENS INLAND AND LONG ISLAND
PINE BARRENS. WINDS IN THE WAKE OF AN UPPER LEVEL DISTURBANCE
SHOULD REMAIN UP OVERNIGHT...SO DO NOT EXPECT THEM TO DECOUPLE
AND PROMOTE RAPID RADIATIONAL COOLING OVER SNOW PACK LIKE
LAST NIGHT.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/...
HIGH PRESSURE MOVES OVER THE AREA SFC AND ALOFT ON THU...WITH
MILDER TEMPS IN THE MID/UPPER 30S BUT STILL RUNNING A LITTLE UNDER
MAV GUIDANCE. SURFACE FLOW STILL EXPECTED TO TURN EASTERLY THU
NIGHT AT THE COAST AND NE OVER THE INTERIOR VIA COLD AIR
DAMMING...WITH LOW LEVEL MOISTENING OVER SNOW PACK POSSIBLY
LEADING TO FOG AND/OR LOW STRATUS LATE THU NIGHT INTO CHRISTMAS
MORNING...AND A CHANCE OF LIGHT RAIN OR DRIZZLE IN THE AFTERNOON.
WITH TEMPS BELOW FREEZING IN MOST SPOTS INITIALLY...IF FOG DOES
OCCUR RIMING ON SURFACES WOULD ALSO BE LIKELY...WHICH COULD
PRODUCE HAZARDOUS DRIVING CONDITIONS LATE THU NIGHT INTO CHRISTMAS
MORNING. TEMPS NOT EXPECTED TO RISE MUCH OVER THE INTERIOR...SO
ICING FROM ANY SPOTTY LIGHT PRECIP COULD REMAIN A PROBLEM WELL
NORTH/WEST OF NYC IN THE AFTERNOON.
HAVE CONTINUED WITH A NAM/GFS BLEND RE TIMING OF STEADIER RAINS
WITH APPROACHING FRONTAL SYSTEM CHRISTMAS NIGHT INTO SAT. COLD AIR
DAMMING SHOULD PROMOTE NE FLOW INLAND...WITH STRENGTHENING E FLOW
AT THE COAST...SO FREEZING RAIN IS EXPECTED NORTH/WEST OF NYC AND
ACROSS SOUTHERN CT...POSSIBLY ALL THE WAY TO THE CT COAST.
NAM/GFS/ECMWF BLEND OF QPF SUGGESTS MAINLY AN ADVISORY EVENT...BUT
CANNOT RULE OUT AREAS OF 1/2 INCH ACCRETION...PARTICULARLY IN
ORANGE COUNTY. IS IT TOO EARLY FOR ANY WATCHES/ADVISORIES...SO
WILL CONTINUE TO MENTION IN HWO AND HIGHLIGHT ON MAIN WEB PAGE.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
THE SECONDARY LOW FROM THIS STORM IS FORECAST TO MOVE OVER OR
NEARBY THE CWA SATURDAY NIGHT INTO SUNDAY MORNING. TEMPERATURES
ALOFT WOULD SUPPORT RAIN THROUGH THE TIME WHEN PRECIPITATION ENDS
FROM WEST TO EAST. WITH A WEAKENING HIGH TO THE NE...SURFACE
TEMPERATURES LIKELY WILL NOT DROP UNTIL THE PRECIPITATION ENDS. SO
GIVEN FORECAST TEMPS RISING ABOVE FREEZING ACROSS THE CWA DURING
THE DAY ON SATURDAY... WILL GO WITH PLAIN RAIN AS PRECIP TYPE
SATURDAY NIGHT.
FOR SUNDAY MORNING...JUST A CHANCE FOR LINGERING RAINFALL ACROSS
EASTERN ZONES...AND SLIGHT CHC ELSEWHERE...OTHERWISE DRY FOR THE REST
OF THE DAY AS AN H5 LOW CENTER MOVES THROUGH THE OHIO VALLEY.
H5 LOW CENTER PROBABLY PASSES THROUGH MONDAY MORNING WITH A SLIGHT
CHANCE OF SNOW SHOWERS OR FLURRIES. LOW PRESSURE IN SE CANADA
DEEPENS THROUGH THE DAY WHILE HIGH PRESSURE BUILDS IN FROM THE WEST.
THE RESULTANT TIGHT PRESSURE GRADIENT WOULD RESULT IN INCREASING
WINDS THROUGH THE DAY WITH HIGH TEMPERATURES AT OR SLIGHTLY BELOW
NORMAL.
A SHOT OF EVEN COLDER AIR IS FORECAST BEHIND A COLD FRONT DROPPING
DOWN OUT OF CANADA LATE MONDAY NIGHT INTO TUESDAY MORNING. AGAIN...A
SLIGHT CHANCE OF SNOW SHOWERS OR FLURRIES DURING THIS TIME. WITH 850
MB TEMPS FALLING TO AROUND -12C...HIGHS ONLY IN THE MID 30S EXPECTED
ON TUESDAY. HIGH PRESSURE THEN DOMINATES THE WEATHER THROUGH THE REST
OF THE LONG TERM WITH DRY WEATHER.
&&
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
VFR FOR THE MAJORITY OF THE NEXT 24 HRS. GUSTY LOW LEVEL WINDS
HAVE GENERALLY SUBSIDED ACROSS THE REGION AND WINDS GENERALLY
UNDER 10KT AT THIS TIME. FORECAST COMPLICATIONS START TO DEVELOP
TONIGHT ACROSS THE AREA. THE FORECAST PROBLEMS ARE GREATEST IN THE
24-30 HR PERIOD FOR KEWR/KJFK. LOW CLOUDS EXPECTED TO DEVELOP
EARLY XMAS MORNING...AND SOME INDICATIONS FROM FORECAST SOUNDINGS
SUGGEST THAT DRIZZLE AND FOG WILL BE A PROBLEM IN ROUGHLY THE
25/08Z-12Z (AND POSSIBLY A FEW HRS BEYOND) TIMEFRAME. FOR NOW HAVE
INTRODUCED SOME LOW CIGS AND -DZ/BR INTO THE KJFK/KEWR TAFS. LOWER
CONFIDENCE YET HIGHER IMPACT IS THAT TEMPS WILL BE WITHIN A FEW
DEGREES OF FREEZING AT THAT TIME AND THIS COULD LEAD TO A FREEZING
DRIZZLE EVENT EARLY XMAS MORNING. FOR NOW HAVE KEPT THE FORECAST
RESTRICTED TO -DZ AND BR...BUT WILL REVISIT LOW LEVEL TEMPERATURES FOR
THE 09Z UPDATE AND FOR ALL TAF SITES FOR THE 12Z TAF ISSUANCE.
OUTLOOK 06Z FRIDAY THROUGH MONDAY...
THURSDAY NIGHT-FRIDAY...SUB-VFR POSSIBLE AFTER MIDNIGHT WITH LOW
CLOUDS AND/OR FOG. -FZDZ ALSO POSSIBLE EARLY FRIDAY MORNING ALL
TAF SITES.
FRIDAY NIGHT-SATURDAY NIGHT...IFR LIKELY. FZRA LIKELY INTO SAT
MORNING FOR KSWF...POSSIBLY KHPN...OTHERWISE RAIN EXPECTED. GUSTY
WINDS POSSIBLE INTO SAT. LLWS ALSO POSSIBLE.
SUNDAY...RAIN TAPERING OFF FROM W-E EARLY SUNDAY MORNING...WITH
VFR RETURNING. GUSTY W WINDS POSSIBLE.
SUN NIGHT-MON NIGHT...-SHSN POSSIBLE SUN NIGHT AND MON NIGHT. COLD
FROPA MON NIGHT WITH GUSTY NW WINDS IN ITS WAKE.
&&
.MARINE...
SCA CONDITIONS WILL PERSIST OVER THE OCEAN THROUGH THU...AND ON
THE EASTERN SOUND/BAYS THROUGH TONIGHT...WITH GUSTS UP TO 25 KT AND
OCEAN SEAS UP TO 6 FT...A FOOT ABOVE WAVEWATCH.
MARGINAL SCA CONDITIONS POSSIBLE FRI ON THE OCEAN VIA
STRENGTHENING EASTERLY FLOW...AND ON ALL WATERS BY SAT. A DECENT
CHANCE OF GALES ON THE OCEAN WATERS SATURDAY AFTERNOON/EVENING
AHEAD OF LOW PRESSURE PASSING OVER OR NEAR THE AREA...OTHERWISE
SCA CONDITIONS ACROSS ALL WATERS...WITH WINDS SUBSIDING THROUGH
THE NIGHT. SCA CONDITIONS BECOME POSSIBLE ONCE AGAIN DURING SUNDAY
AFTERNOON AS THE PRESSURE GRADIENT RE-TIGHTENS. GALES THEN BECOME
POSSIBLE MONDAY AFTERNOON ACROSS THE OCEAN WATERS AND
EASTERN SOUND.
&&
.HYDROLOGY...
SNOW PACK HAS COMPACTED SOMEWHAT...BUT WITH LITTLE IF ANY RUNOFF
OCCURRING AS MAX TEMPS HAVE RISEN NO HIGHER THAN THE 30S.
POTENTIAL EXISTS FOR AN INCH OR MORE OF LIQUID EQUIVALENT QPF...
MAINLY LATE FRI NIGHT THROUGH 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 SAT INTO SUN...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 NOON EST TODAY FOR ANZ350-353-355.
SMALL CRAFT ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR
ANZ330-340.
&&
$$
SYNOPSIS...BG
NEAR TERM...BG
SHORT TERM...BG
LONG TERM...JC
AVIATION...MANNING
MARINE...BG/JC
HYDROLOGY...BG/JC
