000
FXUS61 KBUF 200902
AFDBUF
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
402 AM EST THU NOV 20 2008
.SYNOPSIS...
A CLIPPER SYSTEM CENTERED OVER SOUTHERN ONTARIO THIS MORNING WILL
WEAKEN AND TRACK SOUTHEAST TO NEW YORK CITY TODAY...THEN OFF THE
ATLANTIC COAST TONIGHT. THIS SYSTEM WILL PRODUCE A GENERAL LIGHT
SNOWFALL FOR THE BULK OF WESTERN AND CENTRAL NEW YORK TODAY.
FOLLOWING ITS PASSAGE...A NORTHWESTERLY FLOW OF COLDER AIR WILL
FOLLOW FOR THE REMAINDER OF THE WEEK...WITH LAKE EFFECT SNOWS AGAIN
SETTING UP TO THE SOUTHEAST OF LAKES ERIE AND ONTARIO.
&&
.NEAR TERM /THROUGH TONIGHT/...
LIGHT SNOW FROM THE CLIPPER WILL LINGER INTO THE MORNING, BUT WILL
STRUGGLE TO ACCUMULATE MUCH IN THE BUFFALO AREA DUE TO DRYING FROM
DOWNSLOPING SUBSIDENCE. LIKEWISE THE ROCHESTER AREA WILL NOT SEE
MUCH ACCUMULATION AS THE BULK OF THE SNOW SLIDES TO THE SOUTH AND
THERE WILL ALSO BE A DRYING SOUTHERLY WIND EARLY THIS MORNING.
IN THE AFTERNOON WINDS BEGIN TO LINE UP FROM THE NORTH NORTHWEST. WE
EXPECT UPSLOPE CONVERGENCE TO PROVIDE ENOUGH LIFT FOR 2 TO 3 INCHES
OVER THE CHAUTAUQUA RIDGE INTO THE EVENING AND WITH ANOTHER 3 TO 5
INCHES OVERNIGHT TONIGHT. BOTH THE NAM AND GFS SHOW DECENT QPF, AND
WE HAVE THUS ISSUED A LAKE SNOW ADVISORY STARTING THIS AFTERNOON.
OFF LAKE ONTARIO TERRAIN IS FLATTER WITH LESS CONVERGENCE AND
AMOUNTS SHOULD BE LIGHTER, BUT SNOW SHOWERS ARE LIKELY FROM WAYNE
COUNTY WEST THIS AFTERNOON AND CONTINUING OVERNIGHT.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY/...
AS HAS BEEN THE CASE FOR MUCH OF THIS PAST WEEK...OUR MAIN FORECAST
CONCERN IN THIS PERIOD WILL AGAIN BE LAKE EFFECT POTENTIAL.
00Z NAM AND GFS ARE IN GOOD AGREEMENT THAT A GENERAL NORTHWESTERLY
FLOW OF UNSEASONABLY COLD AIR WILL REMAIN IN PLACE ACROSS THE LOWER
GREAT LAKES REGION THROUGH THIS PERIOD...WITH 850 MB TEMPS HOLDING
STEADY IN THE -14C TO -16C RANGE. WITH LAKE SURFACE TEMPERATURES
GENERALLY AROUND +9C...THIS WILL RESULT IN EXTREME AMOUNTS OF
LAKE-INDUCED INSTABILITY...WITH LAKE EQUILIBRIUM LEVELS AND LAKE
INDUCED CAPES CLIMBING TO AROUND 20 KFT AND 1500 J/KG RESPECTIVELY
BY LATER FRIDAY AFTERNOON/FRIDAY NIGHT...THEN ONLY SLOWLY DROPPING
OFF DURING THE DAY SATURDAY. IN CONJUNCTION WITH THIS
INSTABILITY...SUFFICIENT MOISTURE WILL EXIST IN THE LOWEST 10 KFT OF
THE ATMOSPHERE...ALONG WITH A WELL-DEFINED DENDRITIC SNOW GROWTH
REGION. THESE COMBINATION OF ALL OF THESE INGREDIENTS WILL ADD UP TO
A NEAR CERTAINTY OF SIGNIFICANT LAKE EFFECT SNOWS SOUTHEAST OF THE
LAKES DURING THE SHORT TERM PERIOD...PARTICULARLY FROM FRIDAY
AFTERNOON THROUGH SATURDAY MORNING WHEN THE THERMODYNAMIC
ENVIRONMENT WILL BE MOST FAVORABLE. AS SATURDAY PROGRESSES...
LOW-LEVEL RIDGING AND SOMEWHAT DRIER AIR ALOFT WILL BEGIN WORKING IN
FROM THE CENTRAL GREAT LAKES...RESULTING IN CONDITIONS BECOMING A
LITTLE LESS FAVORABLE...BUT STILL PLENTY GOOD ENOUGH TO SUSTAIN THE
LAKE SNOWS.
OFF LAKE ERIE...AN INITIAL NORTH NORTHWESTERLY FLOW AT THE START OF
THE PERIOD WILL BECOME MORE NORTHWESTERLY ON FRIDAY...THEN WILL
REMAIN SO THROUGH FRIDAY NIGHT...BEFORE POSSIBLY BECOMING A LITTLE
MORE WEST-NORTHWESTERLY ON SATURDAY. THIS SHOULD RESULT IN LAKE
SNOWS PRIMARILY TARGETING CHAUTAUQUA AND CATTARAUGUS COUNTIES FRIDAY
THROUGH FRIDAY NIGHT...BEFORE POSSIBLY SPREADING A LITTLE FURTHER TO
THE NORTH AND EAST ON SATURDAY AS WINDS BACK A LITTLE MORE IN
RESPONSE TO THE APPROACHING LOW LEVEL RIDGE. GIVEN THIS AND THE
LIKELIHOOD OF AN UPSTREAM CONNECTION TO LAKE HURON/ENHANCEMENT FROM
OROGRAPHIC EFFECTS...LAKE EFFECT SNOW WATCHES WILL REMAIN IN PLACE
FOR FRIDAY AND FRIDAY NIGHT FOR CHAUTAUQUA AND CATTARAUGUS
COUNTIES...AND MAY ULTIMATELY NEED TO BE EXPANDED NORTHWARD/EASTWARD
FOR SATURDAY GIVEN THE POTENTIAL FURTHER BACKING OF THE FLOW.
OFF OF LAKE ONTARIO...A GENERAL WEST-NORTHWESTERLY TO NORTHWESTERLY
FLOW WILL TEND TO FAVOR THE STRONGEST LAKE SNOWS FOCUSING ON
WAYNE...NORTHERN CAYUGA...AND OSWEGO COUNTIES DURING THIS
PERIOD...THOUGH SOME ADDITIONAL LAKE SNOWS WILL ALSO BE LIKELY FROM
NIAGARA COUNTY EAST TO MONROE COUNTY...INCLUDING THE GREATER
ROCHESTER AREA. FOR NOW...WILL CONTINUE WITH THE CURRENT LAKE EFFECT
SNOW WATCH FOR THE WAYNE-OSWEGO COUNTY STRIP FOR FRIDAY AND FRIDAY
NIGHT...THOUGH WOULD BET THAT ANY EVENTUAL WARNINGS/ADVISORIES WILL
ULTIMATELY NEED TO BE EXTENDED THROUGH SATURDAY...WITH EXTENSIONS
IN AREA A DEFINITE POSSIBILITY AS WELL GIVEN THE IMPRESSIVE
THERMODYNAMICS AND THE POTENTIAL FOR UPSTREAM CONNECTIONS TO
GEORGIAN BAY.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
THE 00Z RUNS OF THE ECMWF AND THE GFS CONTINUE TO LOOK SIMILAR TO
PREVIOUS RUNS FOR THE SATURDAY NIGHT AND SUNDAY PERIOD...WITH A LOW
AMPLITUDE UPPER RIDGE BUILDING EAST ACROSS THE GREAT LAKES REGION...
AND A SURFACE RIDGE DRIFTING FROM THE APPALACHIANS TO A POSITION OFF
THE MID ATLANTIC COAST. SUBSIDENCE/DRYING AND INCREASING SHEAR
ASSOCIATED WITH THE ADVANCING LOW-LEVEL RIDGE WILL CAUSE ANY LAKE
EFFECT SNOW SHOWERS TO GRADUALLY WIND DOWN LATER SATURDAY NIGHT AND
EARLY SUNDAY...THEN STRENGTHENING WARM ADVECTION ALOFT WILL BRING A
CHANCE OF SOME LIGHT SNOW TO PORTIONS OF THE AREA LATER SUNDAY
AFTERNOON.
LATER ON IN THE PERIOD...THE TWO LONG RANGE MODELS CONTINUE TO
DIVERGE A BIT IN SOLUTIONS...BUT BOTH STILL CLOSE AN UPPER LOW OFF
OVER THE UPPER GREAT LAKES SUNDAY NIGHT BEFORE MOVING IT EASTWARD
EARLY NEXT WEEK. THE CORRESPONDING SURFACE LOW IS FORECAST TO PASS
RIGHT ACROSS OUR CWA MONDAY NIGHT AND TUESDAY...BEFORE DRIFTING OFF
THE ATLANTIC COAST WEDNESDAY. FOR THIS REASON...WE WILL CONTINUE
WITH CHANCE POPS FOR ALL THREE DAYS AT THIS TIME. THE MILDEST DAY OF
THE THREE WILL BE MONDAY...WITH TEMPERATURES WARM ENOUGH FOR A
CHANCE OF RAIN AND SNOW FOR THE DAYLIGHT HOURS THAT DAY...BEFORE
COOLING ENOUGH FOR A CHANCE OF SNOW SHOWERS ON THE BACK SIDE OF THIS
SYSTEM TUESDAY AND WEDNESDAY.
&&
.AVIATION /09Z THURSDAY THROUGH MONDAY/...
CONDITIONS WILL GENERALLY BE MVFR IN LIGHT SNOW WEST OF ROCHESTER
THROUGH THE DAY. MVFR CEILINGS WILL SPREAD TO BETWEEN ROCHESTER
AND SYRACUSE AS WINDS VEER TO THE SOUTHWEST THIS MORNING. IFR
CONDITIONS IN SNOW WILL BE OVER BUFFALO AND NIAGARA FALLS INTO MID
MORNING. JAMESTOWN AND THE WESTERN SOUTHERN WILL LOWER TO IFR IN
SNOW THIS MORNING AND CONTINUE THROUGH THE DAY AS LAKE SNOWS BEGIN
IN THE MIDDLE OF THE DAY. MVFR CEILINGS WILL CONTINUE WEST OF
SYRACUSE TONIGHT...WITH IFR IN SNOW ACROSS JAMESTOWN AND THE
SOUTHERN TIER.
OUTLOOK...
FRIDAY AND SATURDAY...LOCAL IFR IN LAKE EFFECT SNOW SOUTHEAST OF
THE LAKES.
SUNDAY...VFR.
MONDAY...MVFR/IFR IN RAIN OR WET SNOW.
&&
.MARINE...
A CLIPPER SYSTEM CENTERED OVER SOUTHERN ONTARIO THIS MORNING WILL
WEAKEN AND TRACK SOUTHEAST TO NEW YORK CITY TODAY...THEN OFF THE
ATLANTIC COAST TONIGHT. WITH THE LOW EXPECTED TO TRACK RIGHT ACROSS
WESTERN NEW YORK TODAY...WINDS AND WAVES SHOULD GENERALLY REMAIN
BELOW SMALL CRAFT CRITERIA ON BOTH LAKES ERIE AND ONTARIO.
FOLLOWING THE PASSAGE OF THE LOW...A NORTH TO NORTHWESTERLY FLOW OF
COLDER AIR WILL SPREAD ACROSS THE LOWER LAKES TONIGHT...THEN WILL
PERSIST RIGHT THROUGH SATURDAY. DURING THIS LATTER TIME
FRAME...WINDS SPEEDS COULD EVENTUALLY BECOME STRONG ENOUGH TO
PRODUCE ADVISORY-CRITERIA WAVES ACROSS THE LOWER LAKES.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...LAKE EFFECT SNOW WATCH FROM FRIDAY MORNING THROUGH LATE FRIDAY
NIGHT FOR NYZ004>006-019-020.
LAKE EFFECT SNOW ADVISORY FROM NOON TODAY TO 6 AM EST FRIDAY
FOR NYZ019-020.
MARINE...NONE.
&&
$$
SYNOPSIS...JJR
NEAR TERM...APB
SHORT TERM...JJR
LONG TERM...JJR/SAGE
AVIATION...APB
MARINE...JJR
