Lake Effect Snow Warning 1, NWS Green Bay, WI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
400 AM CST WED NOV 19 2008

.SYNOPSIS...LARGE SCALE PATTERN WITH RIDGE IN THE W AND TROF IN THE
E WILL CONT THROUGH THE FCST PERIOD. PATTERN WL GO THROUGH SERIES OF
AMPLIFCATION/DEAMPLIFCATION CYCLES AS SIG SHRTWVS WORK THROUGH THE
PATTERN. TEMPS WL ROLLER COASTER BTWN NR NORMAL TO BLO NORMAL AS
SYSTEMS SHIFT ACRS THE AREA. PCPN WL BE MAINLY LAKE EFFECT...WITH
ANOTHER ROUND OF SIG LAKE-EFFECT EXPECTED EARLY IN THE FCST
PERIOD. MODELS SEEM TO BE COMING INTO BETTER AGREEMENT THAT SHRTWV
CROSSING THE AREA LATE IN THE WEEKEND AND EARLY NEXT WK WL BRIEFLY
PULL THE ERN TROF AXIS WWD...AND THAT WL RAISE THE POSSIBILITY OF
A MORE WIDESPREAD PCPN EVENT.
&&

.SHORT TERM...TDA/TNGT/THU. FOCUS OF THE FCST WAS POTENTIAL FOR SIG
LAKE-EFFECT OFF LAKE SUPERIOR. PATTERN LOOKS PRETTY FAVORABLE. SOME
SHSN WITH THE SYSTEM CROSSING THE AREA ARE POSSIBLE ACRS THE N LATE
THIS AFTN. THEN EXPECT LAKE-EFFECT TO GET GOING TNGT. CONDITIONS
BECOME INCREASINGLY FAVORABLE...WITH A PERIOD OF EXTREME INSTABILITY
AND NEARLY PERFECT TRAJECTORIES LIKELY LATER THU. LARGE SCALE
MOISTURE ALSO PROGGED TO INCR SOME DURING THAT TIME. WL RAMP UP FCST
AND WSW PRODUCTS SOME...BUT STICK WITH WATCH FOR NOW. THAT WL ALLOW
DAY SHIFT TO TAKE ONE LAST LOOK AND MAKE SURE EVERYTHING STAYS
ALIGNED BEFORE COMMITTING TO A WARNING.

NOT MUCH CHG TO FCST ACRS THE REST OF THE AREA. NUDGED TEMPS UP A
BIT ACRS THE SW PART OF THE FCST AREA FOR THIS AFTN...TO ABV GUID
VALUES. EARLY MORNING SFC CHART SHOWED WARM SECTOR LIKELY TO AT
LEAST BRUSH ACRS THAT AREA DURING THE AFTN.

ALSO CONTD WINDY FCST FOR THE DOOR PENINSULA. CURRENT FCST SITTING
JUST BLO ADVISORY CRITERIA. IF LATER DATA SUGGEST ANY FURTHER INCR
IN WINDS THEN AN ADVISORY WL BE NEEDED. WL MENTION IN THE HWO.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY

THE MAIN CONCERN FOR THE LATTER HALF OF THE WEEK IS LAKE EFFECT
SNOW...SPECIFICALLY AMOUNT AND DURATION...IN THE LAKE SUPERIOR
SNOWBELT REGION. HPC PREFERRED A BLEND OF THE ECMWF AND GFS SO
THOSE WERE THE GUIDANCE TOOLS MOST CLOSELY FOLLOWED TO COME UP
WITH THIS FORECAST. 850MB TEMPERATURES AT 00Z FRIDAY WERE
FORECAST TO BE IN THE -15C TO -17C RANGE OVER THE PART OF LAKE
SUPERIOR WHERE THE WATER IS +5C TO +7C. 850MB WARM ADVECTION WILL
START LATE THURSDAY NIGHT BUT INSTABILITY IS EXPECTED TO BE MORE
THAN SUFFICIENT FOR LAKE EFFECT THURSDAY NIGHT. BUFKIT OVERVIEW FROM
THE 00Z GFS INDICATED PLENTY OF AVAILABLE MOISTURE BELOW 6KFT AND
INVERSION HEIGHTS WELL ABOVE THAT. KEPT LAKE EFFECT GOING
THURSDAY NIGHT...ESPECIALLY IN VILAS COUNTY WHERE THEY COULD PICK
UP A FEW MORE INCHES OF SNOW 00Z TO 12Z FRIDAY. MOST OF THE REST
OF THE FORECAST AREA SHOULD HAVE SCATTERED OR ISOLATED SNOW
SHOWERS...WITH FLURRIES EXPECTED IN CENTRAL WISCONSIN. SURFACE
HIGH PRESSURE WILL APPROACH THE STATE...CAUSING SURFACE
WINDS TO BACK TO THE WEST DURING THE DAY ON FRIDAY. THE SNOW
SHOWERS SHOULD THEN PUSH EAST OF MOST OF THE FORECAST AREA DURING
THE DAY ON FRIDAY...AND DEPART THE REMAINDER OF THE AREA BY
EVENING.

CLOUDS SHOULD DECREASE AS THE HIGH DRIFTS OVER THE AREA. AND DRY
CONDITIONS SHOULD PREVAIL FRIDAY NIGHT INTO SATURDAY NIGHT BEFORE
A CLIPPER SYSTEM BRINGS PRECIPITATION CHANCES BACK TO THE AREA
DURING THE EARLY PART OF NEXT WEEK.
&&

.AVIATION...MAV GUID PROBABLY TOO HIGH WITH CIGS...ESP AT RHI. CIGS
COULD DROP INTO MVFR CAT AS WAA CONTS THIS MORNING...AND ARE LIKELY
TO DROP TO MVFR LEVELS ACRS AT LEAST THE NW 1/2 OF THE FCST AREA IN
THE WAKE OF THE COLD FRONT LATE TNGT/TNGT.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW WATCH FROM 00Z/20 TO 12Z21
WIZ005-
&&

SKOWRONSKI/MG

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