FXUS61 KOKX 120840
AFDOKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
340 AM EST SAT DEC 12 2009
.SYNOPSIS...
A HIGH PRESSURE SYSTEM WILL MOVE EAST OFF THE MID ATLANTIC COAST
TONIGHT. LOW PRESSURE IS FORECAST TO DEVELOP OFF THE SOUTHEAST COAST
SUNDAY AND MOVE NORTHEAST PASSING SOUTHEAST OF LONG ISLAND SUNDAY
NIGHT. HIGH PRES WILL FOLLOW MONDAY. A STRONG COLD FRONT WILL MOVE
EAST AND PASS EAST OF THE REGION LATE TUESDAY. THIS WILL BE
FOLLOWED BY A COLD CANADIAN HIGH FOR WEDNESDAY AND THURSDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AS HIGH PRESSURE OVER THE MID ATLANTIC STATES MOVES EAST...COLD
AIR ADVECTION WILL DISSIPATE THIS MORNING. THIS WILL CAUSE WINDS
TO GRADUALLY DECREASE THROUGHOUT THE DAY.
WEST WINDS THIS MORNING WILL VEER TO THE NW AS THE HIGH PRES RIDGE
APPROACHES. UNDER FULL SUN...THIS WILL INCREASE DOWNSLOPE AND CAUSE
SFC TEMP TO RISE NEAR 40 DEGS...HIGHER THAN OUR PREVIOUS FORECAST.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
TONIGHT...AS THE HIGH MOVES OFF THE COAST...SFC WINDS WILL DECOUPLE
FROM THE UPPER FLOW AND CAUSE STRONG RADIATIONAL COOLING UNTIL HIGH
AND MID CLOUDS INCREASE AFTER MIDNIGHT. SFC TEMPS ARE FORECAST TO
FALL INTO THE TEENS W AND N OF NYC INCLUDING INTERIOR SOUTHERN CT
AND THE PINE BARRENS ON LONG ISLAND.
SUNDAY AND SUNDAY NIGHT...FORECAST MODELS ARE IN GOOD AGREEMENT
FOR THE NEXT SYSTEM. THEY SHOW A LOW DEVELOPING ALONG A COASTAL
FRONT OVER THE SOUTHEAST U.S. BY 7 AM SUNDAY THEN TRACKING IT SE
OF LONG ISLAND SUNDAY NIGHT. BASED ON THIS LATEST FORECAST...LIGHT
PRECIP IS FORECAST TO QUICKLY DEVELOP AND MOVE NE ACROSS THE
REGION BETWEEN 10 AM AND 1 PM. OUR STORM TOTAL PRECIP FORECAST
RANGES FROM AROUND 1/2 TO 2/3 OF AN INCH OF LIQUID EQUIVALENT
RAINFALL. SOUNDING FORECAST PROFILES SHOW THE ATMOSPHERE COLD
ENOUGH FOR THE PRECIP TO DEVELOP AS SNOW NW OF NYC. HOWEVER...BASED
ON RAPID WARMING ABOVE THE SFC...SNOW SHOULD QUICKLY CHANGE TO
RAIN NW OF NYC. WHERE CAN THIS FORECAST GO WRONG? FOR AREAS NW OF
NYC...IF SFC TEMPS RISE SLOWER THAN PREDICTED...A PERIOD OF
FREEZING RAIN COULD LEAD TO ICING BEFORE THE CHANGEOVER.
FORECAST CONFIDENCE NW OF NYC...MODERATE.
FORECAST CONFIDENCE ELSEWHERE...HIGH.
MONDAY...A WEAK RIDGE OF HIGH PRESSURE MOVES ACROSS THE REGION
BEFORE THE ARRIVAL OF A STRONGER COLD FRONT.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
MAIN FOCUS IN THE EXTENDED IS ON THE MIDWEEK PERIOD.
AS A COLD FRONT APPROACHES...WARM AIR ADVECTION ALOFT ON SW FLOW
WILL ALLOW FOR INCREASING CLOUDS MON NGT. AT THE SAME TIME...STRONG
SHORTWAVE AT H5 WILL BE DRAWING A CDFNT TOWARDS THE CWA. LIGHT PCPN IS
POSSIBLE IN THE WAA REGIME...AND WITH A DRY START TO THE EVE TEMPS
MAY DROP TO BELOW 32 ACROSS NRN PORTIONS OF THE LOWER HUDSON VALLEY.
THIS WOULD SET THE STAGE FOR SPOTTY -FARA ACROSS THOSE AREAS.
ELSEWHERE...-RA WOULD BE THE PTYPE.
CDFNT SWEEPS THE SUBTROPICAL MOISTURE OFFSHORE TUE WITH A BAND OF RA
POSSIBLE WITH THE FROPA. BOTH THE 12Z GFS/ECMWF PHASE THE SRN AND
NRN STREAM SYSTEMS AND DEVELOP A DEEP LOW NE OF THE CWA TUE NGT AND
WED. PREV RUNS HAVE HINTED AT THIS SCENARIO AS WELL. THE
PLACEMENT/DEPTH/TIMING OF THE SYSTEM HAVE YET TO BE FULLY RESOLVED.
THE FCST FOLLOWS A SOLUTION WHICH DEVELOPS A MODEST 980-985 LOW INVOF
THE MARITIMES. IMPACT TO THE CWA WOULD BE SHSN AS THE STORM
INTENSIFIES NE OF THE CWA WED MRNG WITH STRONG WINDS...CLOSE TO ADVISORY
CRITERIA...WED AND THU. SECONDARY ARCTIC FRONT WED MAY ASSIST IN
SHSN DEVELOPMENT.
THIS SYSTEM BEARS WATCHING AS SOME RUNS HAVE INDICATED DEVELOPMENT
FURTHER S WHICH WOULD BE CONDUCIVE TO A BAND OF SN ON THE BACK SIDE
OF THE LOW...AND SOME RUNS HAVE INDICATED PRESSURES DROPPING INTO
THE 960S ACROSS CANADA WHICH WOULD RESULT IN A HIGH WIND EVENT
ACROSS THE CWA.
TEMPS WILL FALL INTO THE 30S WED WITH A COLD AMS REMAINING IN PLACE
THRU FRI. ALTHO AN ISOLATED SHSN MAY STRAY INTO PORTIONS OF THE
HUDSON VALLEY...THE THU AND FRI FCST IS DRY.
&&
.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
VFR THROUGH THE PERIOD.
GUSTS DIMINISH OUTSIDE CITY TERMINALS OVERNIGHT...RETURNING AFTER
DAYBREAK FOR ALL TERMINALS SAT MORN. WINDS DIMINISH SAT AFTERNOON
INTO SAT EVE AS HIGH BUILDS IN.
INCREASING CIRRUS AND THEN MID-DECK LATE SAT NIGHT.
OUTLOOK 06Z SUN THROUGH TUE...
SAT NIGHT...VFR.
SUN-SUN NGT...SUB-VFR POSSIBLE SUN AFTERNOON/EVENING...WITH
CHANCE OF MIXED PRECIP CHANGING TO RAIN AT THE COAST...AND SNOW
CHANGING TO RAIN OR MIXED PRECIP INTERIOR.
MON...VFR.
TUE...SUB-VFR POSSIBLE WITH COLD FROPA.
&&
.MARINE...
AS LOW PRESSURE MOVES AWAY FROM THE AREA WATERS AND HIGH PRESSURE
BUILD IN...THE PRESSURE GRADIENT WILL START TO RELAX. THUS...WINDS
WILL GRADUALLY DIMINISH THROUGH THE DAY. WIND GUSTS HAVE FALLEN
BELOW GALES AND FOR THE MOST PART ARE EXPECTED TO REMAIN THAT WAY.
THERE MAY HOWEVER BE AN OCCASIONAL GALE GUST EARLY THIS MORNING ONCE
THE SUN COMES UP AND WE START TO MIX A BIT. WITH WINDS
DIMINISHING...SEAS WILL ALSO GRADUALLY DIMINISH FROM 6 TO 9 FT TODAY
TO 4-6 FT BY EVENING. FOR HEADLINES...WILL BE DROPPING THE GALES AND
GOING WITH AN SCA ON ALL WATERS THROUGH TODAY.
AS THE HIGH MOVES OVERHEAD TONIGHT WINDS WILL BE WELL BELOW SCA
LEVELS. FOR NOW...WAVES ARE EXPECTED TO FALL TO AROUND 4 FT TONIGHT
AND ARE NOT PLANNING ON ANY HEADLINES FOR TONIGHT. IF SEAS TAKE A
BIT LONGER TO FALL BELOW 5 FT THAN EXPECTED...THE SCA MAY NEED TO BE
EXTENDED...MAINLY ON THE OCEAN WATERS.
WINDS INCREASE SUNDAY AS LOW PRESSURE MOVES UP THE ATLANTIC COAST.
SCA CONDITIONS WILL MORE THAN LIKELY RETURN...ESPECIALLY IN WAKE OF
LOW PRESSURE SUNDAY NIGHT INTO MONDAY.
THE LOW WILL BE EAST OF MONTAUK BY MONDAY MORNING AND WILL QUICKLY
TRACK EASTWARD THROUGH THE DAY. ANY LINGERING SCA SEAS ON THE OCEAN
WILL SUBSIDE.
SOUTHWEST FLOW WILL INCREASE AHEAD OF A COLD FRONT ON TUESDAY. THESE
WINDS MAY APPROACH MARGINAL SCA LEVELS ON THE OCEAN. THE COLD FRONT
WILL TRACK THRU THE COASTAL WATERS TUESDAY AFTERNOON AND EVENING
WITH LOW PRESSURE DEVELOPING NORTHEAST OF THE WATERS. THIS WILL SET
THE STAGE FOR A PERIOD OF STRONG WINDS AND HAZARDOUS SEAS THRU
THURSDAY. GALES APPEAR LIKELY ATTM.
&&
.HYDROLOGY...
STORM TOTAL PRECIP FOR SUNDAYS EVENT IS FORECAST TO RANGE FROM 1/2
TO 2/3 OF AN INCH...ALL LIQUID FOR COASTAL AREAS. BASED ON HOW
QUICKLY THIS PRECIP ARRIVES AND HOW QUICKLY IT WARMS...UP TO ONE
TENTH OF THIS PRECIP COULD FALL AS SNOW OR FREEZING RAIN FOR AREAS
NW OF NY. THE TIMING IS MAINLY FROM AROUND 10 AM SUNDAY THROUGH
MIDNIGHT.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR
ANZ335-338-340-345.
GALE WARNING UNTIL 6 AM EST EARLY THIS MORNING FOR ANZ330-350-
353-355.
&&
$$
SYNOPSIS...GC
NEAR TERM...GC
SHORT TERM...GC
LONG TERM...
AVIATION...
MARINE...BC
HYDROLOGY...GC
