FXUS61 KOKX 091009
AFDOKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
509 AM EST WED DEC 9 2009
.SYNOPSIS...
HIGH PRESSURE CONTINUES TO SLOWLY RETREATS NORTHEAST TODAY...AS A
STRONG LOW PRESSURE SYSTEM TRACKS ACROSS THE GREAT LAKES...AND A
SECONDARY LOW TRACKS FROM SOUTHEAST VIRGINIA...TO CENTRAL LONG
ISLAND BY THIS AFTERNOON...AND NEAR BOSTON BY THIS EVENING. THESE
TWO STORMS WILL SLOWLY LIFT TO OUR NORTH TONIGHT. HIGH PRESSURE
BUILDS IN FROM THE WEST THROUGH SATURDAY NIGHT...THEN SLIDES
OFFSHORE SUNDAY. A COASTAL LOW COULD THEN IMPACT THE AREA EARLY
NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SNOW WILL CONTINUE ACROSS THE INTERIOR INTO THE RUSH HOUR...WITH
ANY MIXED PRECIPITATION ELSEWHERE CHANGING TO ALL RAIN BY SUNRISE.
ALL READY HAVE RECEIVED REPORTS OF 1 TO 3.5 INCHES OF SNOW MAINLY
FROM ORANGE COUNTY EAST INTO NORTHERN FAIRFIELD COUNTY. OF A BIT
OF A SURPRISE WAS A REPORT OF AROUND 1 INCH OF SNOW IN
STONY BROOK...SUFFOLK COUNTY.
ALL MODELS HAVE SHIFTED THEIR TRACK OF THE COASTAL LOW...AND LOW
LEVEL WARM CORE FURTHER EAST. NAM AND GFS IN FAIRLY GOOD AGREEMENT
ON LOW TRACK (NAM SLIGHTLY SLOWER THAN GFS). WITH THE NAM HANDLING
THE COLD AIR DAMMING BETTER HAVE LEANED TOWARDS THE NAM WITH THIS
SYSTEM. SO FAR PRESSURE FALLS SHOW NAM IS ON TRACK WITH ITS IDEA
OF TAKING THE COASTAL LOW TO SE VA EARLY THIS MORNING...THEN UP TO
AROUND WASHINGTON DC BY AROUND SUNRISE. THE LOW SHOULD THEN TRACK
NE TO CENTRAL LONG ISLAND THIS AFTERNOON.
THIS FURTHER EASTWARD TRACK OF THE COASTAL LOW AND CORE OF LOW
LEVEL WARM AIR...WILL KEEP INTERIOR LOCATIONS COLDER THAN
EXPECTED...AND AS A RESULT...HAVE UPPED SNOW AND ICE TOTALS ACROSS
THE INTERIOR AND EXPANDED THE WINTER WEATHER ADVISORY TO INCLUDE
ALL OF INTERIOR SOUTHERN CONNECTICUT AND INTERIOR NORTHEAST NEW
JERSEY...AS WELL AS NON-COASTAL PORTIONS OF THE LOWER HUDSON
VALLEY. ALSO EXTENDED WINTER WEATHER ADVISORY ACROSS ORANGE/PUTNAM
INTO THE AFTERNOON AS SOME POCKETS OF FREEZING/BELOW TEMPERATURES
WILL LIKELY LAST INTO THE AFTERNOON WITH A RESULT OF FREEZING
RAIN.
USED NAM 2-METER TEMPERATURES AS ENTERING ARGUMENT FOR
TEMPERATURES TODAY...BUT SUSPECT THEY WILL LIKELY END UP BEING TOO
WARM...ESPECIALLY ACROSS ORANGE-NORTHERN PUTNAM COUNTIES WHERE IT
SUFFERS FROM EVEN THE NAM BEING TOO QUICK TO END COLD AIR
DAMMING)...AND ACROSS LONG ISLAND/EASTERN CT WHERE NAM 2-METER
TEMPERATURES USUALLY WARM THINGS TOO MUCH IN WARM AIR MASS
BEHIND/TO THE EAST OF THE COASTAL LOW...AND DEFINITELY TOO MUCH
WET OF THE COASTAL LOW (MAV NUMBERS SEEMED REASONABLE ACROSS
WESTERN LONG ISLAND AND NYC AS A RESULT).
ALL MODELS ALSO EXTENDED THE DURATION OF RAINFALL TODAY...SO HAVE
KEPT POPS CATEGORICAL ALL DAY...EXCEPT OVER FAR WESTERN AREAS
WHERE LOWER TO LIKELY (CHANCE FAR WESTERN ORANGE COUNTY).
IN COORDINATION WITH HPC...DID UNDERCUT MODEL QPF SLIGHTLY...BUT
WITH BANDING POTENTIAL DECIDED TO KEEP FLOOD WATCH UP EVERYWHERE
(THOUGH FLOODING NOW LESS LIKELY ACROSS AREAS WITH 2+ INCHES OF
SNOW). SEE HYDROLOGY SECTION FOR FURTHER DETAILS.
WIND ADVISORY CONTINUED AS IS FOR LONG ISLAND/COASTAL CT/IMMEDIATE
NEW YORK CITY METRO THROUGH 2 PM. STILL EXPECT GUSTY E WINDS AHEAD
OF THE COASTAL LOW OF 25-30 MPH WITH GUSTS TO 45-50 MPH. THERE
SHOULD BE A LULL IN THE WINDS STARTING AROUND MID AFTERNOON...WITH
PRESSURE GRADIENT RELAXED IN VICINITY OF COASTAL LOW CROSSING THE
REGION.
&&
.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
CROSSING COLD FRONT COUPLED WITH LF QUADRANT OF 150+ KNOT 300 HPA
JET WARRANTS CHANCE POPS FOR SHOWERS THIS EVENING. ENOUGH COLD
AIR COULD WORK IN ACROSS THE NORTHERN TIER THAT THEY COULD MIX
WITH/CHANGE TO SNOW SHOWERS BEFORE ENDING THERE. WINDS INCREASE
WITH STRONG COLD ADVECTION AND HAVE ISSUED WIND ADVISORY FOR THE
SAME AREA AS THE CURRENT ONE + ESSEX AND UNION COUNTIES IN NJ
FROM 8PM TONIGHT THROUGH 6AM THURSDAY WITH WEST WINDS OF 25-30
MPH GUSTING TO 45 TO 50 MPH EXPECTED. WINDS SHOULD DIMINISH
ENOUGH IN LOW LEVELS...THAT WHILE GUSTY WINDS WILL CONTINUE INTO
FRIDAY...THEY SHOULD REMAIN BELOW ADVISORY LEVELS.
OTHER THAN THE WIND...THE MAIN STORY IN THE SHORT TERM WILL BE
BELOW NORMAL TEMPERATURES...AS THE COLDEST AIR MASS OF THE FALL
BUILDS INTO THE REGION AHEAD OF CANADIAN HIGH PRESSURE BUILDING IN
FROM THE WEST. EXPECT HIGHS THURSDAY TO STRUGGLE TO REACH THE
UPPER 30S/AROUND 40...LOWS THURSDAY NIGHT IN THE TEENS ACROSS THE
INTERIOR AND 2OS ELSEWHERE (ABOUT 10 DEGREES BELOW NORMAL) WITH
WIND CHILLS FROM THE SINGLE DIGITS TO LOWER TEENS). HIGHS FRIDAY
WILL STRUGGLE TO REACH THE UPPER 20S ACROSS THE INTERIOR AND THE
FREEZING MARK ELSEWHERE (12-15 DEGREES BELOW NORMAL) AND WIND
CHILLS INN THE TEENS. LOWS FRIDAY NIGHT WILL BE SIMILAR TO
THURSDAY NIGHT...EXCEPT OVER LONG ISLAND...WHERE DIMINISHING
WINDS WILL ALLOW FOR THE PINE BARRENS TO COOL OFF LIKE THE
INTERIOR. WIND CHILLS WILL BE IN THE SINGLE DIGITS FRIDAY NIGHT.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
00Z ECMWF/GFS HAVE CHANGED THEIR TUNE FROM THE 12Z VERSIONS...SO
HAVE TWEAKED THE EXTENDED TOWARDS THE NEW RUNS. FIRST CHANGE WAS
TO DELAY THE IMPACT OF THE COASTAL LOW FOR EARLY NEXT WEEK TO
SUNDAY NIGHT/MONDAY (SHOULD BE DRY BEFORE THEN). LOOKS LIKE IT
WILL BE COLD ENOUGH FOR A LIGHT SNOW AT MOST LOCATIONS (COASTAL
LOW CURRENTLY FORECAST TOO FAR S FOR ANYTHING MORE THAN THAT)
ECMWF/GFS DIVERGE AFTER THAT IN TERMS OF TIMING SYSTEMS (THOUGH
DO AGREE ON A WARMER SOLUTION THAN THE 12Z MODELS) SO BASICALLY
HAVE PUT IN SLIGHT CHANCE POPS MONDAY/TUESDAY AND TRENDED
TEMPERATURES UPWARDS (THOUGH NOT AS WARM AS 00Z GUIDANCE SUGGESTS
TO HELP GUARD AGAINST ANY FLIP-FLOPS WITH FUTURE RUNS).
&&
.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
FIRST BANDS OF PRECIPITATION ASSOCIATED WITH THE STRENGTHENING
COMPLEX LOW PRESSURE SYSTEM TO THE WEST/SOUTHWEST ARE MOVING
THROUGH AT THIS TIME. PRECIP AT MOST TERMINALS HAS EITHER BEGUN
AS SNOW OR QUICKLY TRANSITIONED OVER TO SNOW WITH ACCOMPANYING
IFR/LIFR CONDITIONS... BUT THINK DURATION OF SNOW AT NYC AREA
TERMINALS SHOULD LAST NO LONGER THAN ABOUT 09Z AS EASTERLY FLOW
QUICKLY RAMPS UP AND ADVECTS WARMER AIR INTO THE NYC AREA. TIMING
OF CHANGE TO RAIN LESS CERTAIN AT KHPN/KBDR/KGON...AND UNSCHEDULED
AMENDMENTS ARE LIKELY THERE. SNOW SHOULD CONTINUE THROUGH THE
NIGHT AT KSWF...WITH A CHANGE TO FREEZING RAIN/SLEET AFTER
DAYBREAK...BUT CHANGE TO PLAIN RAIN THERE ALSO UNCERTAIN.
EASTERLY FLOW SHOULD QUICKLY STRENGTHEN LATE TONIGHT AS SECONDARY
LOW PRESSURE ZIPS UP THE COAST TOWARD LONG ISLAND...AND EXPECT
SUSTAINED WINDS CLOSE TO 25 KT WITH GUSTS 35-40 KT TOWARD MORNING
AND LASTING THROUGH ABOUT MIDDAY ...ALSO LLWS AT SOME TERMINALS.
IFR/LIFR IN MODERATE-HEAVY RAIN LIKELY AT ALL TERMINALS AFTER
DAYBREAK...WITH TIMING OF CHANGE TO RAIN AT KSWF UNCERTAIN. ALSO
CANNOT RULE OUT A RUMBLE OF THUNDER AT KISP/KGON THIS AFTERNOON
AS THE LOW PASSES OVERHEAD OR JUST TO THE EAST.
IFR/LIFR LIKELY TO PERSIST INTO THIS EVENING UNTIL AFTER COLD
FROPA THIS EVENING. FROPA MAY BE ACCOMPANIED BY A RUMBLE OF
THUNDER...AND FOLLOWED BY VERY STRONG WSW WINDS.
OUTLOOK 06Z THU THROUGH SUNDAY...
LATE WED NIGHT...VFR WITH STRONG WSW WINDS.
THU-FRI...VFR WITH GUSTY W WINDS.
FRI NIGHT-SAT...VFR WITH DIMINISHING WINDS.
SUN...SUB-VFR POSSIBLE.
&&
.MARINE...
GALE WARNING REMAINS UNCHANGED. THERE WILL LIKELY BE A LULL IN THE
WINDS FROM AROUND MIDDAY THROUGH THIS EARLY EVENING AS A SECONDARY
LOW PRESSURE CENTER PASSES THROUGH THE WATERS. BEHIND THE
STORM...HIGH PRESSURE BUILDS IN AND THE PRESSURE GRADIENT RE-
TIGHTENS WITH A GUSTY WESTERLY FLOW THIS EVENING. FORECAST
SOUNDINGS SHOW THE BOUNDARY LAYER WELL-MIXED FOR SEVERAL HOURS.
GALE WARNING WILL PROBABLY NEED TO BE EXTENDED INTO THURSDAY
NIGHT ACROSS THE OCEAN ZONES. WILL LET LATER SHIFTS REASSESS THIS.
SEAS EXPECTED TO BUILD UP INTO THE 10-15 FT RANGE TODAY. ALTHOUGH
WAVES IN THE SURF ZONE MAY APPROACH 8 FT ALONG THE SOUTH SHORE OF
LONG ISLAND...DOMINANT WAVE PERIOD IS FORECAST TO REMAIN BELOW 10
SECONDS AS WINDS SHIFT OFFSHORE THIS AFTERNOON. WILL THEREFORE
HOLD OFF ON ISSUING A HIGH SURF ADVISORY.
THE PROLONGED TIGHT PRESSURE GRADIENT SHOULD HAVE WINDS AT LEAST
UP TO SMALL CRAFT ADVISORY LEVELS THROUGH FRIDAY NIGHT. WINDS AND
SEAS THEN DIMINISH THROUGH THE DAY ON SATURDAY WITH THE CENTER OF
THE BUILDING HIGH CLOSER TO THE EASTERN SEABOARD. A COASTAL STORM
MAY BUILD WINDS AND SEAS AGAIN SATURDAY NIGHT INTO SUNDAY.
&&
.HYDROLOGY...
2 TO 2.5 INCHES LIQUID/LIQUID EQUIVALENT PRECIPITATION IS FORECAST
FOR TUESDAY NIGHT THROUGH WEDNESDAY...WITH LOCALLY HIGHER AMOUNTS
POSSIBLE. WHILE THE MAIN IMPACT IS EXPECTED TO BE URBAN/SMALL STREAM
FLOODING...IT COULD BE WIDESPREAD ENOUGH TO HAVE SIGNIFICANT IMPACT
ON THE MORNING RUSH. THE FLASH FLOOD WATCH HAS BEEN CONTINUED AS
A RESULT.
THOUGHT ABOUT CANCELING OVER THE INTERIOR WITH NOW MORE SNOW/ICE
EXPECTED...BUT WITH POTENTIAL FOR BANDING...ESPECIALLY ON TOP OF
ICED OVER SNOW PACK...AM NOT COMPLETELY CONVINCED FLOOD THREAT IS
LOW ENOUGH TO WARRANT DROPPING THE WATCH OVER THE INTERIOR AT THIS
TIME.
QPF AMOUNTS SHOULD BE MAXIMIZED DURING THE 5AM TO 11AM TIME FRAME.
0.5 TO 1.0 INCH PER HOUR RATES ARE POSSIBLE DURING THIS PERIOD.
&&
.TIDES/COASTAL FLOODING...
BASED ON LATEST TRENDS...IT APPEARS ONLY FAR WESTERN LONG ISLAND
SOUND MAY JUST TOUCH MINOR COASTAL FLOODING WITH THE HIGH TIDE
CYCLE OCCURRING EARLY THIS MORNING. DON'T THINK MINOR COASTAL
FLOODING WILL BE WIDESPREAD ENOUGH TO WARRANT AN ADVISORY.
WINDS WILL DIMINISH AS THEY SHIFT INTO AN OFFSHORE DIRECTION BEFORE
THE HIGH TIDE CYCLE THIS AFTERNOON. GUIDANCE DOES NOT INDICATE
MINOR COASTAL FLOODING WITH THIS TIDE CYCLE...AND PILING FROM THIS
MORNING'S CYCLE PROBABLY WON'T BE A CONCERN.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...WIND ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR CTZ009>012.
WIND ADVISORY FROM 8 PM THIS EVENING TO 6 AM EST THURSDAY FOR
CTZ009>012.
FLASH FLOOD WATCH THROUGH THIS AFTERNOON FOR CTZ005>012.
WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR CTZ005>008.
NY...WIND ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR NYZ071>081.
WIND ADVISORY FROM 8 PM THIS EVENING TO 6 AM EST THURSDAY FOR
NYZ071>081.
FLASH FLOOD WATCH THROUGH THIS AFTERNOON FOR NYZ067>081.
WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NYZ069-070.
WINTER WEATHER ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR
NYZ067-068.
NJ...WIND ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR NJZ006.
WIND ADVISORY FROM 8 PM THIS EVENING TO 6 AM EST THURSDAY FOR
NJZ005-006-011.
FLASH FLOOD WATCH THROUGH THIS AFTERNOON FOR NJZ002>006-011.
WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NJZ002>004.
MARINE...GALE WARNING UNTIL 6 AM EST THURSDAY FOR ANZ330-335-338-340-
345-350-353-355.
&&
$$
PUBLIC/HYDROLOGY...MALOIT
AVIATION...BG
MARINE AND TIDES/COASTAL FLOODING...JC
