FXUS61 KOKX 242325
AFDOKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
625 PM EST THU DEC 24 2009
.SYNOPSIS...
ANOTHER MAJOR STORM SYSTEM WILL IMPACT THE COUNTRY OVER THE
HOLIDAY WEEKEND....THIS TIME AROUND THOUGH...THE HEAVY SNOW FALL
OVER THE UPPER MIDWEST AND NORTHERN PLAINS. THE ASSOCIATED FRONTAL
SYSTEM WILL BRING RAINS TO THE AREA STARTING FRIDAY EVENING AND
CONTINUING INTO SATURDAY NIGHT. CONDITIONS WILL DRY OUT ON SUNDAY
FOLLOWING A COLD FRONTAL PASSAGE IN THE MORNING. AFTER A WEAK AREA
OF LOW PRESSURE MOVES ACROSS THE AREA MONDAY...AN ARCTIC COLD FRONT
WILL FOLLOW MONDAY NIGHT. DRY...UNSEASONABLY COLD CONDITIONS WILL
FOLLOW FOR THE MIDDLE OF NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
A MAJOR STORM SYSTEM WILL UNFOLD ACROSS THE MID SECTION OF THE
COUNTRY THE NEXT 24H AS THE TWO BRANCHES OF THE POLAR JET BECOME
PHASED. OUT AHEAD...STRONG RIDGING BOTH ALOFT AND AT THE SFC WILL
BUILD ACROSS EASTERN CANADA AND THE NORTHEAST. AS THE RIDGE AXIS
SLIDES EAST OF THE AREA LATE TONIGHT...SFC WINDS WILL VEER AROUND
TO THE NE. THIS WILL ALLOW FOR ATLANTIC LOW-LEVEL MOISTURE TO WORK
INTO THE AREA BENEATH A STRENGTHENING LOW-LEVEL INVERSION. LATEST
VIS IMAGERY SHOWS STRATUS ALONG THE NEW ENGLAND COAST DROPPING TO
THE SE. OVERNIGHT THIS STRATUS WILL EXPAND IN COVERAGE WITH MOST
LOCATIONS BECOMING MOSTLY CLOUDY BY DAYBREAK.
THE ONSHORE FLOW AND CLOUD COVER WILL KEEP TEMPS WARMER THAN
RECENT NIGHTS...25-30 AT THE COAST AND THE TEENS INLAND. WEAK LOW-
LEVEL WARM ADVECTION MAY PRODUCE A SPRINKLE OVERNIGHT...BUT NOT
MUCH MORE AS THE BEST LIFT SEEMS OCCUR ABOVE THIS LAYER.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
A STRONG UPPER VORTEX OVER THE MID SECTION OF THE COUNTRY WILL BE
SLOW TO TRANSLATE EAST THIS PERIOD. THE ASSOCIATED FRONTAL
BOUNDARY WILL APPROACH THE EASTERN SEABOARD ON FRI WITH A WEAK
WAVE FORMING ALONG IT OVER THE MID ATLANTIC STATES. IT IS THIS
WAVE AND THE WARM ADVECTION OUT AHEAD OF IT THAT WILL PRODUCE
INCLEMENT WEATHER THROUGH THE FIRST HALF OF THE HOLIDAY WEEKEND.
WHILE THERE WILL BE A LOW PROBABILITY OF PCPN FRI AFT...THE BULK
OF THE RAIN WILL OCCUR FRI NIGHT THRU SAT NIGHT. THE STRONG POLAR
HIGH RETREATING OFF THE NEW ENGLAND COAST AND ATLANTIC MOISTURE
OVERRUNNING IT WILL CAUSE SOME DAMMING OF COLD AIR...ESPECIALLY
ACROSS THE LOWER HUDSON VALLEY AND INTERIOR SW CT. TEMPS WILL BE
MARGINAL AND COLDEST ACROSS ORANGE COUNTY FRI NIGHT INTO SAT
MORNING.
AT THIS TIME...IT APPEARS THAT THERE WILL NOT BE ENOUGH ICE
ACCRETION TO WARRANT A WATCH AND THAT THIS EVENT WILL FALL ALONG
THE LINES OF AN ADVISORY. CONFIDENCE TO ISSUE A THIRD PERIOD
ADVISORY WITH A MARGINALLY COLD AIR MASS IS ALSO TOO LOW AT THIS
TIME. THE HAZARDOUS WEATHER OUTLOOK (HWO) WILL CONTINUE TO BE THE
VEHICLE FOR THIS INFORMATION WITH THE DETAILS IN THE GRIDDED
FORECASTS. POTENTIAL DOES EXIST FOR UP TO A QUARTER INCH OF ICE
WELL NORTH AND WEST OF NYC BEFORE CHANGING OVER TO PLAIN RAIN BY
NOON SAT. SRN CT AND NE NJ WILL SEE SOME ICE ACCRETION...BUT TO A
LESSER EXTENT.
A STRONG EAST FLOW ON SAT WILL SCOUR OUT ANY SUB-FREEZING AIR BY
AROUND NOON WITH LIGHT TO OCCASIONALLY MODERATE RAINFALL SAT AFT
AND NIGHT. WITH THE SNOW PACK IN PLACE...ESPECIALLY ACROSS EASTERN
LI AND SE CT...THERE IS LIKELY TO BE POOR DRAINAGE FLOODING
PROBLEMS. RIVER AND STREAMS SHOULD BE ABLE TO HANDLE THE ONE INCH
OF RAINFALL FORECAST FOR THE REGION.
CONDITIONS DRY OUT SUN MORNING WITH THE PASSAGE OF THE COLD FRONT.
SUN WILL BE MILD WITH A WESTERLY FLOW AND HIGHS IN THE 40S.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
THE LONG TERM IS CLASSIFIED AS A RETURN TO WINTER. STRONG COLD
ADVECTION RESULTS IN A RARE FALLING OF AFTERNOON TEMPS PATTERN ON
MONDAY WITH PASSAGE OF UPPER TROUGH (ASSUMING TIMING IS ON TRACK).
GFS RUNNING A BIT SLOWER THEN THE GEM. LATEST GEFS SUPPORTS THE
SLOWER GFS. IN TERMS OF PCPN...CHC POPS WITH ALL INDICATIONS THAT
PCPN WOULD BE LIGHT - I USED SHOWERS...BUT WOULD EXPECT MORE OF
PERIODS OF LIGHT PCPN. P-TYPE...WHILE MIXED WITH RAIN ON THE COAST
INITIALLY (AM)...SHOULD HAVE NO PROBLEM CHANGING TO ALL SN WITH A
LIGHT ACCUMULATION.
ARCTIC FRONT PASSES MONDAY EVENING - FLURRIES. LEAVING A VERY COLD
AND WINDY TUESDAY. TEMPS PROBABLY TOO HIGH IN FCST FOR
TUESDAY...COULD STAY IN THE 20S ALL THE WAY TO THE COAST.
HIGH PRESSURE HOLDS IN UNTIL NEW YEARS WITH SLOWLY MODERATING TEMPS
WHEN MODELS SUGGEST ANOTHER COASTAL STORM POTENTIAL.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
HIGH PRES OVER WRN QUEBEC WILL CONTINUE TO SLIDE EWD TNGT. THIS
WILL ALLOW FOR LGT N WINDS TO VEER TO THE ENE. LOW CLOUDS AT BKN-
OVC025 SHOW UP ON STLT ACROSS SERN CT AND ERN LI...TRACKING TO
THE SW AT AROUND 25 KT. TAF THEREFORE BRINGS MVFR INTO THE METRO
2-3Z. STLT INDICATES SOME NWD EXPANSION OF STRATUS WHICH IS
ABUNDANT OVER THE OCEAN.
SOME BREAKS TO VFR ACROSS KGON THRU 3Z TIL STRATUS EXPANDS N
AGAIN.
MVFR CONTINUES FRI WITH ONSHORE ENE FLOW. MAIN LIFT COMES FRI
NGT...3Z OR LATER...WHICH WILL PRODUCE RA S COAST AND -FZRA
INLAND. FOR NOW...KHPN ALL RA...BUT THIS MAY CHANGE IN SUBSEQUENT
FCSTS. KBDR MAY SEE A PERIOD OF -FZRA AS WELL. MVFR WITH PERIODS
OF IFR. WINDS WILL STEADILY INCREASE.
OUTLOOK 06Z SATURDAY THROUGH MONDAY...
FRIDAY NIGHT-SATURDAY NIGHT...IFR LIKELY. FZRA LIKELY INTO SAT
MORNING FOR KSWF...POSSIBLY KHPN...OTHERWISE RAIN EXPECTED. GUSTY NE
WINDS POSSIBLE INTO SAT. LLWS 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...
SFC HIGH PRES BUILDS OFFSHORE ON FRI WITH A STRENGTHENING ELY FLOW
AHEAD OF THE APPROACHING COLD FRONT. SCA SEAS EXPECTED ON FRI WITH
GALE FORCE WINDS POSSIBLE ON THE OCEAN WATERS FRI NIGHT THRU SAT.
WINDS IN THE MIXED LAYER GET UP TO 45 KT...WHICH SHOULD TRANSLATE
TO GALE FORCE GUSTS ON THE OCEAN. FOR THE REMAINING WATERS...
STRONG SCA CONDITIONS CAN BE EXPECTED. WINDS WILL DIMINISH SAT
NIGHT...BUT SEAS WILL BE SLOW TO SUBSIDE.
NW GALES LIKELY DEVELOP DURING THE DAY ON MONDAY AND CONTINUE
INTO TUESDAY DUE TO STRONG COLD ADVECTION IN RESPONSE DEEPENING
LOW PRESSURE OVER THE CANADIAN MARITIMES.
HIGH PRESSURE FOR MID WEEK WITH TRANQUIL CONDITIONS.
&&
.HYDROLOGY...
POTENTIAL EXISTS FOR AROUND AN INCH OF LIQUID EQUIVALENT QPF...
MAINLY LATE FRI NIGHT THROUGH SUN MORNING. THIS POTENTIAL QPF
FALLS ON TOP OF SNOW PACK WITH A WATER EQUIVALENT RANGING FROM 1/2
TO 1 INCH FROM NYC NORTH AND WEST TO UP TO 3 INCHES OVER EASTERN
LI AND SE CT. THE COMBINATION OF THE SNOW PACK AND MODERATE RAIN
WILL LIKELY LEAD TO URBAN FLOODING. RIVER AND STREAM FLOODING
NORTH AND WEST OF NYC IS LESS LIKELY TO OCCUR DUE TO LESS OF A
SNOW PACK.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM FRIDAY TO 6 PM EST SATURDAY FOR
ANZ330-335-338-340-345.
GALE WATCH FROM FRIDAY EVENING THROUGH SATURDAY AFTERNOON FOR
ANZ350-353-355.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 6 AM TO 6 PM EST
FRIDAY FOR ANZ350-353-355.
&&
$$
SYNOPSIS...DW
NEAR TERM...DW
SHORT TERM...DW
LONG TERM...JST
AVIATION...JMC/BS
MARINE...DW/JST
HYDROLOGY...DW
