FXUS61 KOKX 250542
AFDOKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
1242 AM EST FRI DEC 25 2009
.SYNOPSIS...
CANADIAN HIGH PRESSURE SLOWLY RETREATS NORTHEAST INTO SATURDAY. AN
AREA OF LOW PRESSURE WILL DEVELOP OVER THE MID ATLANTIC STATES
SATURDAY NIGHT THEN TRACK NORTHEAST TO THE TRI-STATE SUNDAY
MORNING...AND TO THE GULF OF MAINE BY SUNDAY EVENING...WITH ITS
TRAILING COLD FRONT PASSING THROUGH THE REGION SUNDAY NIGHT. AN
ARCTIC COLD FRONT WILL THEN PUSH THROUGH THE AREA LATE
MONDAY...FOLLOWED BY CANADIAN HIGH PRESSURE BUILDING IN THROUGH
THE MIDDLE OF NEXT WEEK. A STORM SYSTEM WILL APPROACH FROM THE
SOUTHEASTERN UNITED STATES ON THURSDAY.
&&
.NEAR TERM /UNTIL 6 AM THIS 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.
SATELLITE IMAGERY CONTINUES TO SHOW STRATUS ALONG THE COAST
WORKING SW. EXPECT THIS TREND TO CONTINUE OVERNIGHT AS LOW- LEVEL
FLOW BECOMES MORE EASTERLY. MOST LOCATIONS BECOMING MOSTLY CLOUDY
BY DAYBREAK.
THE ONSHORE FLOW AND CLOUD COVER WILL KEEP TEMPS WARMER THAN
RECENT NIGHTS...UPPER 20S/LOWER 30S AT THE COAST AND THE
TEENS/LOWER 20S INLAND. SOME PATCHY FREEZING FOG POSSIBLE ACROSS
INTERIOR VALLEYS BEFORE CLOUD COVER INCREASES LATE. WEAK LOW-
LEVEL WARM ADVECTION MAY PRODUCE A SPRINKLE OVERNIGHT...BUT NOT
MUCH MORE AS THE BEST LIFT SEEMS OCCUR ABOVE THIS LAYER. BLACK ICE
WILL CONTINUE TO BE A PROBLEM ON UNTREATED SURFACES...SO HAVE
ISSUED SPS TO DETAIL CONCERN.
&&
.SHORT TERM /6 AM THIS 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 PRECIPITATION FRI AFT...THE BULK
OF THE RAIN WILL OCCUR FRI NIGHT THROUGH 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 PRECIPITATION...CHANCE POPS WITH ALL INDICATIONS THAT
PRECIPITATION WOULD BE LIGHT - I USED SHOWERS...BUT WOULD EXPECT MORE OF
PERIODS OF LIGHT PRECIPITATION. 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 /06Z FRIDAY THROUGH TUESDAY/...
HIGH PRESSURE OVER CENTRAL QUEBEC WILL CONTINUE TO SLIDE EASTWARD
TOWARDS LABRADOR INTO CHRISTMAS MORNING. THIS WILL ALLOW FOR LIGHT
NORTHEAST WINDS TO VEER TO THE EAST-NORTHEAST. LOW CLOUDS HAVE
OVERSPREAD LONG ISLAND/SOUTHERN NYC METRO TERMINALS. SATELLITE INDICATES
SOME NORTH/WESTWARD EXPANSION OF THE STRATUS WHICH IS ABUNDANT
OVER THE OCEAN. TAFS THEREFORE EXPAND THE MVFR NORTH/WESTWARD AS
WELL.
MVFR CONTINUES CHRISTMAS DAY WITH ONSHORE ENE FLOW. MAIN LIFT COMES
CHRISTMAS NIGHT...0-3Z OR LATER...WHICH WILL PRODUCE RA COAST
AND -FARA INLAND. FOR NOW...KHPN ALL RA...BUT THIS MAY CHANGE IN
SUBSEQUENT FORECASTS. KBDR MAY SEE A PERIOD OF -FARA AS WELL. MVFR
WITH PERIODS OF IFR. WINDS WILL STEADILY INCREASE AS THE GRADIENT
TIGHTENS.
OUTLOOK 06Z SATURDAY THROUGH MONDAY...
LATE FRIDAY NIGHT-SATURDAY NIGHT...IFR LIKELY. RAIN. WARM FRONT
WILL REMAIN OVER THE OCEAN...SO KSWF MAY STAY FARA THROUGH AT LEAST
18Z..AND POSSIBLY KHPN INTO THE EARLY MORNING HOURS FRI NIGHT. E
WINDS 15 TO 25 KT...HIGHEST COAST. LLWS WHERE SFC WINDS ARE AT OR
BELOW 10KT.
SUNDAY AND SUNDAY NIGHT...COLD FRONT DRIVES THE PRECIPITATION OFFSHORE
AND ALLOWS FOR A WIND SHIFT TO THE W BETWEEN 12-16Z. BECOMING VFR.
MONDAY AND MONDAY NIGHT...CHANCE SHSN WITH ARCTIC COLD FRONT...WITH
GUSTY WINDS BEHIND FRONT. POSSIBLE LOW PRESSURE DEVELOPMENT OFF
THE COAST WOULD RESULT IN SN CHANCES DEPENDING ON TRACK.
TUESDAY...VFR WITH GUSTY NW WINDS.
&&
.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 THROUGH 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 THIS EVENING TO 6 PM EST
SATURDAY FOR ANZ330-335-338-340-345.
GALE WATCH FROM THIS EVENING THROUGH SATURDAY AFTERNOON FOR
ANZ350-353-355.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 6 AM THIS MORNING
TO 6 PM EST THIS EVENING FOR ANZ350-353-355.
&&
$$
SYNOPSIS...DW/MALOIT
NEAR TERM...NV
SHORT TERM...DW
LONG TERM...JST
AVIATION...MALOIT/JMC
MARINE...DW/JST
HYDROLOGY...DW
