FXUS61 KOKX 230818
AFDOKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
318 AM EST WED DEC 23 2009
.SYNOPSIS...
LOW PRESSURE PASSES TODAY USHERING A REINFORCING SHOT OF COLD
AIR. HIGH PRESSURE BUILDS SOUTH FROM ONTARIO TONIGHT THROUGH
CHRISTMAS EVE. ONSHORE FLOW AHEAD OF AN APPROACHING FRONT WILL
BRING PRECIPITATION FRIDAY NIGHT INTO SATURDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
LATEST IR FG PRODUCT ILLUSTRATES CLOUDS REMAIN N AND NW OF THE CWA
AS OF 7Z. THIS WILL NOT LAST LONG AS A COMPACTED H5 CYCLONE EVIDENT
IN THE 6.7U SATELLITE PICTURE PIVOTS FM NORTHERN NEW ENGLAND S THRU
EASTERN MASS. NO PRECIPITATION IS FORESEEN WITH THIS FEATURE DUE
LACK OF SUFFICIENT MOISTURE /PWATS LESS THAN 0.30 INCHES/. A PERIOD
OF STRATOCU IS PREDICTED DURING THE MIDDAY AND AFTERNOON
HOURS...ESPECIALLY EAST OF THE CITY. THE SYSTEM EXITS TONIGHT
OWING TO DECREASING CLOUDS...HOWEVER WITH A MID LEVEL SHORTWAVE
CROSSING OVERHEAD...SCATTERED MID CLOUDS WILL BE AROUND. BOUNDARY
LAYER COLD ADVECTION COUPLED WITH LOWEST SUN ANGLE OF THE YEAR
EQUATES TO NO MORE THAN A TEN DEGREE TEMPERATURE SPREAD FROM DAWN
READINGS. ALL GUID HAS COME IN A FEW DEGREES COOLER THAN INHERITED
FORECAST...SO ADJUSTED MAXT DOWNWARD WITH MOST PLACES BELOW 32F
TODAY.
&&
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
HIGH CONFIDENCE FORECAST WITH A SURFACE ANTICYCLONE NOSING SOUTH
FROM ONTARIO YIELDING DRY BUT CONTINUED BELOW NORMAL WEATHER. FAST
FLOW AT MID LEVEL LEADS TO PASSING ALTOCU...BUT PLENTY OF SUNSHINE
AS WE APPROACH CHRISTMAS. H8 TEMPERATURES SURPASS 0C THUR AFTN...SO
THAT WILL HELP ERODE EXISTING SNOW PACK. MAXT SHOULD BE AROUND
40F THUR. SURFACE FLOW TURNS EASTERLY THURSDAY NIGHT AND THAT
COULD LEAD TO FOG WITH WEAK WAA OVER SNOWPACK. CONTINUED MENTION
OF PATCHY FOG IN THE SUITE OF TEXT AND DIGITAL PRODUCTS.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
HIGH PRES SLOW TO DEPART THE REGION FRI AS CLOSED LOW OVER THE UPPER
MIDWEST SLOWLY TRACKS EAST. WITH SLOWER TRACK FAVORED BY 00Z/23
ECMWF AND NAM...WILL PUSH BACK START TIME OF HIGHER POPS UNTIL LATE
FRI NIGHT/SAT...THEN WILL BUMP UP POPS TO LOW-END CATEGORICAL SAT
NIGHT.
WITH 1040 MB HIGH ACROSS EASTERN CANADA FRI NIGHT THROUGH SAT
MORNING...COLD AIR AT THE SFC SHOULD BE TRAPPED WITH ONSET OF PRECIP
AND A WIDESPREAD FREEZING RAIN EVENT IS POSSIBLE ACROSS THE LOWER
HUDSON VALLEY AND INTERIOR CT DURING THIS TIME. TEMPS WARM UP ABOVE
FREEZING SAT MORNING...THEN SHOULD STAY ABOVE FREEZING FOR BULK OF
THE EVENT. COLD FRONT OUT AHEAD OF THE NEARLY VERTICALLY STACKED
CLOSED LOW OVER THE UPPER MIDWEST APPROACHES DURING THE DAY
SAT...AND A SECONDARY LOW WILL DEVELOP OVER THE DELMARVA AREA
SAT...LIFTING THROUGH THE LOCAL AREA SAT NIGHT. BOTH THE GFS AND THE
ECMWF FAVOR BRINGING A SLUG OF HEAVY PRECIP THROUGH THE REGION SAT
NIGHT...SO WILL MENTION RAIN HEAVY AT TIMES.
HEAVY RAIN AND MELTING SNOWPACK WILL LIKELY LEAD TO FLOODING
ISSUES...WITH LOCAL RIVER RISES ACROSS THE INTERIOR AND URBAN
FLOODING ACROSS NYC/LONG ISLAND.
SYSTEM DEPARTS ON SUN...AND PRECIP TAPERS OFF.
MIDWEST STORM SYSTEMS SIGNIFICANTLY WEAKENS BY THE TIME IT TRACKS
ACROSS THE LOCAL AREA EARLY IN THE NEW WEEK. WILL ONLY CARRY SLIGHT
CHANCE POPS.
A STRONG NW FLOW WILL DEVELOP MON AND TUE...WITH TEMPERATURES
DROPPING BACK INTO THE 30S FOR HIGHS.
HIGH PRES BUILDS OVER THE AREA WED.
&&
.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
VFR...THOUGH THERE IS BEGINNING TO BE SOME INDICATION THAT THERE
COULD BE A PERIOD OF MVFR CEILINGS THIS AFTERNOON/EARLY THIS
EVENING. CONFIDENCE IS NOT HIGH ENOUGH TO REFLECT IN TAF...SO
JUST PLAY AS LOW END VFR FOR NOW.
GUSTY NW WINDS DIMINISH SLIGHTLY OVERNIGHT AND BACK TO THE WNW
OVER SOUTHERN TERMINALS...THEN PICK BACK UP AGAIN (10-15G20-25KT)
OUT OF THE NW THIS MORNING (14-15Z). WINDS DIE DOWN AGAIN
WEDNESDAY EVENING AT INTERIOR TERMINALS
OUTLOOK 06Z WEDNESDAY THROUGH SUNDAY...
LATE WEDNESDAY NIGHT-THURSDAY...VFR.
THURSDAY NIGHT-FRIDAY...SUB-VFR POSSIBLE WITH LOW CLOUDS AND/OR
FOG. -FZRA OR -FZDZ ALSO POSSIBLE INLAND FRI AFTERNOON
(KHPN/KSWF). FRIDAY NIGHT-SATURDAY NIGHT...SUB VFR. FZRA POSSIBLE
INTO SAT MORNING FOR KSWF/KHPN...OTHERWISE WINTRY MIX/RAIN
BECOMING ALL RAIN FRIDAY NIGHT (LOWEST CHANCE OF MIX
KLGA/KJFK/KEWR). GUSTY ENE-E WINDS FRI NIGHT BECOMING SE
SATURDAY...THEN S SATURDAY NIGHT. LLWS ALSO POSSIBLE.
SUNDAY...RAIN LIKELY TAPERING OFF FROM W-E STARTING SUNDAY
AFTERNOON...WITH VFR RETURNING.
&&
.MARINE...
SCA CONDITIONS PERSIST OVER EASTERN L.I. SOUND AND THE OCEAN WATERS
THROUGH TNGT AND PERHAPS THUR MORNING. AS LOW PRESSURE MOVES
OFFSHORE...BUT THE PRESSURE GRADIENT REMAINS STRONG ENOUGH TO REACH
THE GUST CRITERIA.
SCA CONDITIONS LIKELY WITH MARGINAL GALES ON THE OCEAN WITH
PASSAGE OF STORM SYSTEM FRI THROUGH SUN. SCA CONDITIONS LIKELY
EARLY IN THE NEW WEEK WITH STRONG NW FLOW.
&&
.HYDROLOGY...
MELTING OF SNOW PACK CONTINUES THU-FRI AS TEMPS CLIMB TO NEAR 40F IN
NYC METRO AND COASTAL SECTIONS.
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...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 6 AM EST THURSDAY FOR ANZ350-353-
355.
SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ330-
340.
&&
$$
SYNOPSIS...98
NEAR TERM...98
SHORT TERM...98
LONG TERM...MPS
AVIATION...PFM
MARINE...98/MPS
HYDROLOGY...98/MPS
