Lake-Effect Snow in New York, January 19 to 20, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BUFFALO NY
334 AM EST FRI JAN 19 2007

.SYNOPSIS...

AFTER BEING PAMPERED FOR THE FIRST HALF OR SO OF WINTER...WE WILL
BE IN THE GRIPS OF TYPICAL WESTERN NEW YORK CONDITIONS FOR MUCH OF
THE NEXT SEVEN TO TEN DAYS. DURING THIS PERIOD WE WILL EXPERIENCE
NEAR TO BELOW NORMAL TEMPERATURES WITH FAIRLY FREQUENT BOUTS OF
SNOW.

THIS WILL INCLUDE MODERATE TO HEAVY LAKE EFFECT SNOW TODAY THROUGH
SATURDAY FOR SITES SOUTHEAST OF BOTH LAKES ERIE AND ONTARIO. LAKE
EFFECT SNOW WATCHES HAVE BEEN UPGRADED TO WARNINGS AND ADVISORIES
AS A RESULT...WITH SOME AREAS WELL SOUTH OF BUFFALO AND SOUTHEAST
OF LAKE ONTARIO RECEIVING 1 TO AS MUCH AS 2 FEET OF SNOW BY
SATURDAY EVENING. DETAILS ARE FOUND BELOW.

&&

.SHORT TERM /TODAY THROUGH SUNDAY/...

A FAIRLY VIGOROUS SHORTWAVE CROSSING WESTERN NEW YORK THIS MORNING
WILL PRODUCE WIDESPREAD SNOW FOR THE ENTIRE FORECAST AREA...WITH
MOST LOCATIONS PICKING UP AN INCH OR TWO OF ACCUMULATION. LAKE
ENHANCEMENT WILL PRODUCE SLIGHTLY HIGHER AMOUNTS IN THE BUF METRO
AREA. THE WIDESPREAD SNOW WILL THEN TAPER OFF TO SCATTERED SNOW
SHOWERS DURING THE MIDDAY AND AFTERNOON AS THE SHORTWAVE WILL
RAPIDLY EXIT THE REGION VIA NEW ENGLAND.

THE SYNOPTIC SNOW WILL TRANSITION TO LAKE EFFECT DURING THE COURSE
OF THE MORNING AND EARLY AFTERNOON. INITIALLY...THE ACTIVITY OFF
LK ERIE WILL BE DOMINANT WITH A WELL ALIGNED 290 FLOW PRODUCING
ACCUMS OF 3 TO 6 INCHES FOR SITES WELL SOUTH OF BUFFALO. THE LAKE
EFFECT SNOW WARNING WILL THUS GO INTO EFFECT AT ISSUANCE.

THE ACTIVITY OFF LK ONTARIO WILL TAKE A FEW MORE HOURS TO GET
GOING...BUT SHOULD BE IN PLACE BY THIS AFTERNOON AS A 290-300 FLOW
WILL BE IN PLACE. SNOWFALL AMOUNTS OF 2 TO 4 INCHES WILL BE COMMON
FROM WAYNE COUNTY TO OSWEGO COUNTY WITH THE LES WARNING GOING INTO
EFFECT AT 18Z.

FOR BOTH LAKES...THE LAKE EFFECT PARAMETERS WILL BE VERY FAVORABLE
TONIGHT. THEY INCLUDE...
 LAKE DELTA TS OF ABOUT 15
 CAPS IN THE VICINITY OF 10K FT
 LAKE INDUCED CAPES AVG 500 J/KG
 AND WELL ALIGNED 300 DEG BOUNDARY LAYER WINDS.

THE POTENTIAL FLY IN THE OINTMENT WILL BE THE PASSGAGE OF AN
ARCTIC FRONT LATE TONIGHT AND EARLY SATURDAY MORNING. THIS
BOUNDARY WILL PRODUCE A BURST OF MODERATE TO HEAVY SNOW FOR THE
VAST MAJORITY OF THE REGION AS IT MOVES SOUTH...BUT IT MAY ALSO
TEMPORARILY BREAK UP THE LAKE SNOWBANDS. POPS HAVE BEEN RAISED TO
CAT FOR THE ENTIRE FORECAST AREA FOR THIS PERIOD AS A RESULT OF
THE ARCTIC FRONTAL PASSAGE.

MUCH COLDER AIR WILL THEN POUR ACROSS THE REGION DURING THE COURSE
OF SATURDAY WITH BOUNDARY LAYER WINDS VEERING TO MORE OF A 330
DIRECTION. LAKE DELTA TS WILL INCREASE TO NEARLY 20 WITH
BORDERLINE EXTREME INSTABILITY. WHILE THE WINDS WILL REMAIN FAIRLY
WELL ALIGNED...THE SHORTER FETCH WILL RESULT IN MORE OF A MULTI-
BAND CONFIGURATION OF THE LES.

THE LAKE SNOWS WILL THUS SPREAD TO THE WEST ACROSS MONROE AND
ORLEANS COUNTIES WHERE SEVERAL INCHES OF ACCUMULATION IS LIKELY.

THE LAKE SNOWS WILL THEN TAPER OFF TO SCATTERED LIGHT SNOW SHOWERS
SATURDAY NIGHT AS THE CAP WILL COME DOWN AND DRIER AIR WILL BECOME
ENTRAINED INTO THE BOUNDARY LAYER FROM MID LEVELS.

OUTSIDE OF THE LAKE EFFECT AREAS...IT WIL BE COLD SATURDAY
AFTERNOON AND NIGHT WITH A FEW SNOW SHOWERS AND TEMPS DROPPING
WELL BELOW NORMAL VALUES.

A FLAT RIDGE WILL CROSS THE AREA ON SUNDAY TO BRING AN END TO THE
LAKE EFFECT ACTIVITY...BUT THE RESPITE WILL BE SHORT LIVED AS A
WEAK SHORTWAVE WILL BE ON OUR DOORSTEP WITH MORE SNOW EXPECTED FOR
SUNDAY NIGHT.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...

THIS PERIOD WILL FEATURE BELOW NORMAL TEMPERATURES AS A GREENLAND
BLOCK (-NAO PHASE) WILL REMAIN IN PLACE THROUGH THE PERIOD. AS A
RESULT OF THIS...SEVERAL STORMS ARE EXPECTED TO SLIDE DOWN THE
CHUTE FROM CENTRAL CANADA TO BRING US FREQUENT BOUTS OF SNOW.
SOME DETAILS...

SUNDAY NIGHT...THE CUTOFF LOW OVER SOUTHERN CA WHICH BROUGHT SOME
UNUSUAL CONVECTIVE SNOW TO THAT PART OF THE COUNTRY WILL MOVE
THROUGH THE DESERT SOUTHWEST ON SATURDAY AND START TO EJECT
NORTHEASTWARD ON SUNDAY.  THE GFS MOVES THIS WEAKENING SYSTEM OVER
WESTERN NY LATE SUNDAY NIGHT.  ITS A STRETCH AS THE GFS IS MORE
AMPLIFIED THAN THE GFS ENSEMBLE MEMBERS...BUT WILL KEEP A CHANCE OF
SHOWERS IN THE FORECAST FOR THIS.

EXPECT A BREAK ON MONDAY...THEN A WEAK COLD FRONT ON TUESDAY.
THINGS COULD GET INTERESTING ON THE MESOSCALE BEGINNING ABOUT
TUESDAY NIGHT THROUGH THURSDAY WITH A SOUTHWEST FETCH AND COLD
AIRMASS...TARGETING THE BUF METRO AREA FOR LAKE EFFECT SNOW.  WILL
KEEP THE PROBABILITY AT 50 PERCENT OR SO THIS IS FAR OUT...THAT
IS...WILL NOT GET CARRIED AWAY YET.  THE POTENTIAL IS THERE
HOWEVER...PARTICULARLY WEDNESDAY AS A UPPER LEVEL SYSTEM TOGETHER
WITH A SURFACE LOW MOVES SOUTHEASTWARD TOWARD THE UPPER GREAT
LAKES.  THIS SYSTEM WORKS THROUGH ON THURSDAY WITH WINDS BECOMING
NORTHWESTERLY.  WILL ADD SOME WORDING TO THE HAZARDOUS WEATHER
OUTLOOK REGARDING THIS POTENTIAL.

&&

.AVIATION /08Z-06Z/...

CIGS AND VSBYS WILL BE MAINLY IN THE MVFR RANGE WITH SNOW SHOWERS
ACROSS WESTERN NEW YORK WITH VSBYS OCCASIONALLY DROPPING TO IFR.
EAST OF LAKE ERIE CONDITIONS ARE EXPECTED TO DROP FROM IFR
CONDITIONS IN SNOW SHOWERS THIS MORNING TO LIFR TO VLIFR IN
LOCALIZED HEAVIER LAKE SNOWS LATER THIS AFTERNOON AND INTO TONIGHT.
THESE TYPE OF CONDITIONS ARE ALSO EXPECTED TO DEVELOP SE OF LAKE
ONTARIO LATER THIS AFTERNOON AND THIS EVENING. UP ACROSS THE FART
NORTH COUNTRY MVFR CIGS AND VFR VSBYS ARE EXPECTED TO DROP TO THE
MVFR RANGE IN SNOW SHOWERS AFTER AROUND 12Z OCCASIONALLY LOWERING TO
LIFR VSBYS AND IFR CIGS IN SNOW SHOWERS UNTIL AROUND 16Z WHEN
CONDITIONS SHOULD IMPROVE BACK TO VFR.

&&

.MARINE...

SMALL CRAFT ADVISORYS ARE IN EFFECT FOR THE NEARSHORES OF LAKES ERIE
AND ONTARIO THROUGH SATURDAY AS A TIGHT PRESSURE GRADIENT DEVELOPS
OVER THE REGION. A GALE WARNING CONTINUES IN EFFECT INTO SATURDAY
FOR THE OPEN WATERS OF LAKE ONTARIO. LOW PRESSURE IS FORECAST TO
DEEPEN RAPIDLY THIS AFTERNOON AND EVENING OFF THE NEW ENGLAND COAST.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...LAKE EFFECT SNOW WARNING UNTIL 5 PM EST SATURDAY FOR NYZ019-
     020-085.
     LAKE EFFECT SNOW WARNING FROM 1 PM THIS AFTERNOON TO 5 PM EST
     SATURDAY FOR NYZ004>006.
     LAKE EFFECT SNOW ADVISORY UNTIL 10 PM EST THIS EVENING FOR
     NYZ012.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 AM EST SATURDAY FOR LEZ020-040-
         041.
         GALE WARNING FROM NOON TODAY TO 6 PM EST SATURDAY FOR
         LOZ062>065.
         SMALL CRAFT ADVISORY UNTIL 6 PM EST SATURDAY FOR
         LOZ042>044.
         SMALL CRAFT ADVISORY UNTIL 6 PM EST SATURDAY FOR LOZ045.

&&

SYNOPSIS...RSH
SHORT TERM...RSH
LONG TERM...ZAFF/RSH
AVIATION...JJP
MARINE...JJP

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