FXUS61 KOKX 030227
AFDOKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
927 PM EST WED DEC 2 2009
.SYNOPSIS...
DEEPENING LOW PRESSURE WILL MOVE FROM THE OHIO RIVER VALLEY THIS
EVENING TO NEAR NOVA SCOTIA THURSDAY EVENING...WITH ITS ASSOCIATED
WARM FRONT LIFTING THROUGH LATE TONIGHT...AND TRAILING COLD FRONT
CROSSING THE AREA THURSDAY MORNING INTO EARLY THURSDAY AFTERNOON.
HIGH PRESSURE WILL BUILD IN FROM THE SOUTHWEST FROM LATE THURSDAY
THROUGH MONDAY...THEN SLIDE OFFSHORE MONDAY NIGHT AND TUESDAY.
MEANWHILE...A COASTAL LOW WILL PASS SOUTHEAST OF LONG ISLAND
SATURDAY AND SATURDAY NIGHT. A COMPLEX STORM SYSTEM WILL THEN
IMPACT THE REGION DURING THE MIDDLE OF NEXT WEEK.
&&
.NEAR TERM /THROUGH THURSDAY NIGHT/...
UPDATED EARLIER TO BRING CAT POP FOR OCCASIONAL RAIN INTO THE AREA
A LITTLE SOONER THAN FORECAST. NOW FOR WINDS...QUICK LOOK AT SFC
OBS OVER ERN VA/NC AND 18Z NAM SUGGEST ABOUT 90 PERCENT MIXING
EFFICIENCY OF LOW LEVEL JET. EXTRAPOLATING THIS NORTHWARD LATE
TONIGHT INTO THU MORNING SUGGESTS THAT THE WESTERN PORTION OF THE
WIND ADVISORY AREA (NYC METRO) MAY FALL SHORT OF STRICT
CRITERIA...BUT WITH GUSTS UP TO 40 MPH STILL LIKELY WILL STAY THE
COURSE. OF GREATER CONCERN IS THE 80-KT 950-975 MB LOW LEVEL JET
FCST BY 18Z NAM TO SIDESWIPE THE SOUTH FORK OF LONG ISLAND.
MAY NEED TO UPGRADE THAT AREA TO HIGH WIND WARNING...WILL BE
LOOKING AT 00Z NAM DATA AND COLLABORATING WITH BOX BEFORE MAKING
ANY FINAL DECISION THERE.
TEMPS ARE REMAINING NEARLY STEADY ATTM AND SHOULD SLOWLY RISE AS
WINDS INCREASE OVERNIGHT...REACHING THE MID 50S TO AROUND 60 ONCE
THE WARM FRONT GOES THROUGH LATE TONIGHT. BASICALLY FOLLOWED BLEND
OF MET GUIDANCE AND 18Z NAM WITH MINOR ADJUSTMENTS.
VALID PORTION OF PREV DISCUSSION...
THE 12Z NAM/GFS WERE FAIRLY SIMILAR WITH LARGE SCALE FEATURES IN
THE NEAR TERM. WHERE THERE ARE DIFFERENCES IN THE DETAILS...THE
SREF WAS A REASONABLE COMPROMISE BETWEEN THE TWO...AND SO WAS USED
AS THE BASIS FOR THE NEAR TERM.
CONDITIONS WILL RAPIDLY DETERIORATE THIS EVENING...WITH WINDS
RAPIDLY INCREASING...REACHING WIND ADVISORY CRITERIA OVER LONG
ISLAND/NEW YORK CITY/COASTAL CT/INTERIOR SE CT AFTER MIDNIGHT. DID
NOT POST A WIND ADVISORY OVER THE LOWER HUDSON VALLEY/NE
NJ/INTERIOR SW CT AS CORE OF LOW LEVEL JET IS FORECAST TO TRACK
OVER/JUST EAST OF THE TWIN FORK WITH A FAIRLY SHARP DIMINISHING OF
WIND SPEED TO THE WEST OF THE CORE. DUE TO EXPECTED DEVELOPMENT OF
FAIRLY SHARP LOW LEVEL INVERSION DO NOT HAVE NEEDED 80 PERCENT
CONFIDENCE TO GO WITH A HIGH WIND WARNING OVER EASTERN LONG ISLAND
AND COASTAL SE CT...BUT COULD END UP CLOSE TO CRITERIA...ESPECIALLY
SUSTAINED WIND OVER THE TWIN FORKS. WINDS WILL BE AT THEIR
STRONGEST A COUPLE OF HOURS ON EITHER SIDE OF SUNRISE AS THIS IS
WHEN THE LOW LEVEL JET WILL CROSS/PASS JUST EAST OF THE FAR
EASTERN PORTION OF THE CWA.
RAIN WILL CONTINUE THROUGH THE NIGHT...TAPERING OFF FROM W TO E
THURSDAY MORNING AS THE LOW PULLS AWAY. EXPECT THE HEAVIEST RAIN
OVERNIGHT AS 850 AND SURFACE WARM FRONT PUSH THROUGH THE REGION
(SEE HYDROLOGY SECTION FOR MORE DETAILS ON QPF). THERE IS ENOUGH
LOW LEVEL INSTABILITY AND FORCING WITH THIS WARM FRONTAL PASSAGE
THAT ELEVATED THUNDER IS POSSIBLE AS WELL OVERNIGHT. FOR NOW IT
APPEARS THE ELEVATED NATURE OF THE CONVECTION AND THE LOW LEVEL
INVERSION SHOULD PRECLUDE THE MIXING DOWN OF WARNING CRITERIA
WINDS (THOUGH THIS CANNOT BE COMPLETELY RULED OUT).
SKY CONDITIONS SHOULD FAIRLY RAPIDLY CLEAR OUT...AND WINDS DIE
DOWN THURSDAY AFTERNOON...WITH MAINLY CLEAR SKY CONDITIONS AND
LIGHT WINDS EXPECTED THURSDAY NIGHT.
HIGHS THURSDAY WILL OCCUR IN THE MORNING (AROUND 60-MID
60S...EXCEPT MID TO UPPER 50S FAR NW)...THEN EXPECT SLOWLY FALLING
TEMPERATURES THURSDAY AFTERNOON BEHIND THE COLD FRONT. FOLLOWED
MET GUIDANCE.
WITH MAINLY CLEAR SKY CONDITIONS AND LIGHT WINDS...TEMPERATURES
SHOULD FALL OF FAIRLY RAPIDLY THURSDAY NIGHT...USED THE COLDER OF
MET/MAV NUMBERS FOR LOWS.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
FORECAST COMPUTER MODELS SHOW AN UPPER LEVEL SHORT WAVE TROUGH
ROTATING AROUND A LARGE CUTOFF POLAR LOW BETWEEN THE UPPER GREAT
LAKES AND JAMES BAY CANADA.
BECAUSE THERE ARE DIFFERENCES IN THE AMPLITUDE AND TIMING OF THIS
ROTATING TROUGH...THIS IS A LOW CONFIDENCE FORECAST FOR A LIGHT
PRECIPITATION EVENT SATURDAY AFTERNOON AND NIGHT.
LOW PRES IS FORECAST TO DEVELOP OF THE SE COAST SAT MORNING AND
TRACK OFFSHORE. THE NAM MODEL SHOWS THIS LOW SLOWER AND FURTHER
WEST. THE GFS MODEL SHOWS THIS LOW FASTER AND FURTHER EAST. WILL
CONT WITH A CHANCE OF POPS...RAIN/SNOW ALONG THE COAST AND SNOW INLAND
SAT AFTERNOON AND CHANCE OF SNOW THROUGHOUT THE AREA SAT NIGHT.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
PRECIP WINDS DOWN EARLY AM SUN AS THE SFC LOW LIFTS OFF TO THE
NORTHEAST. HIGH PRESSURE BUILDS INTO THE REGION LATER SUN INTO
MON...WITH DRY CONDITIONS PREVAILING THROUGH TUE. THE NEXT CHANCE OF
PRECIP ARRIVES LATE ON WED IN ASSOCIATION WITH A SYSTEM MOVING OUT
OF THE OHIO AND MISSISSIPPI VALLEYS.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
LOW OVER THE OHIO VALLEY MOVES NORTHEAST THROUGH THE FORECAST
PERIOD WITH A COLD FRONTAL PASSAGE 10Z TO 15Z. CEILINGS AND
VISIBILITIES WILL LOWER TO IFR THROUGH 06Z...AND REMAIN UNTIL 11Z
TO 13Z AS THE RAIN ENDS AND CONDITIONS IMPROVE. SOME UNCERTAINTY
WITH THE TIMING OF THE LOWERING OF THE CEILINGS AND
VISIBILITIES...AND THE ONSET OF GUSTY WINDS. A PERIOD OF HEAVY
RAIN IS POSSIBLE...ALONG WITH AN ISOLATED THUNDERSTORM FROM ABOUT
06Z TO 10Z. PROBABILITY OF THUNDER AT ANY TERMINAL IS LOW. LOW
LEVEL WIND SHEAR IS ALSO POSSIBLE FOR A BRIEF TIME...ESPECIALLY
RIGHT ALONG THE COAST OF LONG ISLAND...KISP...AND KGON.
WINDS WILL BE THE MAIN ISSUE WITH SUSTAINED WIND AROUND 20 KT AND
SOME GUSTS UP TO 35 KT. SOUTHERLY WINDS SHIFT TO THE WEST WITH THE
COLD FRONTAL PASSAGE.
OUTLOOK 00Z FRIDAY THROUGH MONDAY...
THU NIGHT THROUGH FRI NIGHT...VFR.
LATE SAT AND SAT NIGHT MVFR TO IFR IN RAIN AND SNOW.
SUN TROUGH MON...VFR.
&&
.MARINE...
ON TRACK FOR SOLID GALE FROM AROUND MIDNIGHT TONIGHT INTO THU.
THINK LOW LEVEL INVERSION WILL PREVENT MIXING OF STORM FORCE
WINDS FROM ALOFT...WITH LATEST FCST SOUNDINGS SHOWING VERY LITTLE
WIND SPEED VARIABILITY IN THE LOWEST LEVELS (MAYBE 5 KT)...SO
WHILE AN ISOLATED GUST TO STORM FORCE IS POSSIBLE... ESPECIALLY
OVER THE WATERS AROUND EASTERN LONG ISLAND...DO NOT THINK IT WILL
BE PREVALENT ENOUGH TO WARRANT STORM WARNINGS. WINDS DIE DOWN
BELOW GALE FORCE DURING THE DAY ON THU FROM W TO E. EXPECT SMALL
CRAFT ADVISORIES TO REPLACE THE GALES ON ALL WATERS ONCE THE GALE
CONDITIONS HAVE ENDED. EXPECT WINDS TO FALL BELOW SCA LEVELS ON
ALL WATERS BY THE END OF THURSDAY NIGHT (LASTLY ACROSS THE EASTERN
OCEAN WATERS).
STRONG SE-S WINDS TONIGHT...THEN SW WINDS ON THU WILL BUILD SEAS
ON THE OCEAN WATERS TO 7 TO 13 FT AND 4 TO 7 FT ON THE SOUND BY
MORNING...BOTH HIGHEST EAST. SEAS SHOULD FALL BELOW SCA CRITERIA
ON THE SOUND BY LATE THU...BUT REMAIN ABOVE SCA CRITERIA ON THE
OCEAN WATERS THU NIGHT.
SCA CONDITIONS ARE POSSIBLE EARLY FRI...THEN SEAS SUBSIDING LATER
IN THE DAY. SEAS MAY BUILD ABOVE SCA CRITERIA AGAIN ON THE OCEAN
SAT NIGHT-SUN MORNING AS A COASTAL LOW PASSES SOUTH/EAST OF THE
LOCAL AREA. THEN QUIET CONDITIONS SHOULD FOLLOW FOR SUNDAY
AFTERNOON AND BEYOND AS HIGH PRESSURE BUILDS INTO THE REGION.
&&
.HYDROLOGY...
EXPECT AROUND 12 HOURS OF RAIN TONIGHT...LOCALLY HEAVY AT
TIMES...ESPECIALLY IN ASSOCIATION WITH ANY ISOLATED CONVECTION.
LOOK FOR 1 TO 1.5 INCHES OF RAIN...HIGHEST EAST...WITH LOCALLY
HIGHER AMOUNTS. MAIN THREAT IS FOR URBAN POOR DRAINAGE FLOODING.
AFTER THINGS DRY OUT THURSDAY MORNING...NO OTHER SIGNIFICANT
PRECIPITATION (0.5 INCHES OR MORE) IS EXPECTED THROUGH EARLY
NEXT WEEK.
A PASSING COASTAL LOW SATURDAY COULD BRING A FEW TENTHS OF AN INCH
OF LIQUID...WITH SOME OF IT FALLING AS SNOW...SO NO HYDROLOGIC
IMPACT IS EXPECTED.
&&
.TIDES/COASTAL FLOODING...
GUIDANCE WAS RUNNING 0.5 TO 1.5 FT TOO LOW THIS AFTERNOON...SO
ADJUSTING FOR THIS AND EXPECTED STORM TIMING...EXPECT MINOR
COASTAL FLOODING ALONG THE COAST OF THE SOUND AND THE BACK BAYS
OF LONG ISLAND/NYC. DEPARTURES WILL RUN ABOUT 1.5 FT ABOVE
NORMAL...WITH MODERATE FLOODING BENCHMARKS BEING APPROACHED ALONG
THE FAR WESTERN SOUND (BUT LIKELY NOT EXCEEDED DUE TO THE
RELATIVELY SHORT DURATION OF THE STRONG SE WINDS).
WITH WAVES BUILDING TO 8-10 FT AT ATLANTIC BEACHES THU...HAVE
ISSUED A HIGH SURF ADVISORY THERE...ALSO HIGHLIGHTING THE
POTENTIAL FOR BEACH EROSION.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...WIND ADVISORY UNTIL 11 AM EST THURSDAY FOR CTZ007>012.
COASTAL FLOOD ADVISORY FROM 8 AM TO NOON EST THURSDAY FOR
CTZ009>012.
NY...WIND ADVISORY UNTIL 11 AM EST THURSDAY FOR NYZ071>081.
COASTAL FLOOD ADVISORY FROM 8 AM TO NOON EST THURSDAY FOR
NYZ071-073-075>081.
HIGH SURF ADVISORY FROM 5 AM THURSDAY TO MIDNIGHT EST THURSDAY
NIGHT FOR NYZ075>077-080-081.
NJ...NONE.
MARINE...GALE WARNING UNTIL 5 PM EST THURSDAY FOR ANZ330-340-345-350-
353-355.
GALE WARNING UNTIL 11 AM EST THURSDAY FOR ANZ335-338.
&&
$$
SYNOPSIS...BG/PFM
NEAR TERM...BG/PFM
SHORT TERM...GC
LONG TERM...FIG
AVIATION...MET
MARINE...FIG/GC/PFM
HYDROLOGY...PFM
TIDES/COASTAL FLOODING...
