Lake-Effect Snow in Wisconsin, December 4 to 5, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
325 PM CST TUE DEC 4 2007

ATTENTION IS ON CLIPPER SYSTEM MOVING THRU TONIGHT AND LAKE EFFECT
POTENTIAL.

.SHORT TERM...AREA 88-D RADAR MOSAIC SHOWS NARROW BAND OF HEAVIEST
SNOW ALIGNING WELL WITH AXIS OF BEST ISENTROPIC ADIABATIC OMEGA
ON 290K SFC AND 850-700MB Q-VECTOR CONVERGENCE....WHICH MOVES
ACROSS THE SOUTHWEST 3/4 OF THE CWA TONIGHT.

SATURATION OF DRY LAYER AT AND BELOW 600MB OVER RGN...SHOWN ON
12Z DVN AND GRB RAOBS HAS DELAYED ONSET OF SNOW AT SFC BY AN HOUR
OR TWO. ONCE SATURATION OCCURS...VSBYS QUICKLY GO FROM 5 MILES OR
BETTER TO UNDER 2 MILES...WITH 1/2 TO 3/4 MILES UNDER THE HIGHER
REFLECTIVITY BANDS. BEST SNOW ACCUMULATIONS WILL BE BETWEEN 3 PM AND
9 PM IN WRN COUNTIES...AND 6 PM AND MIDNIGHT IN THE EAST....WITH
HPC AND MODEL QPF PRODUCING 3 TO 5 INCH TOTALS BY 12Z WED MORNING
OVER THE ADVISORY AREA...WITH 2 TO 3 INCH AMOUNTS IN FOND DU LAC
AND SHEBOYGAN COUNTIES.

OPERATIONAL MODELS STILL INDICATING LAKE-EFFECT SNOW SHOWERS IN
WAKE OF SYTEM SNOW. 1000-850MB MOISTURE CONVERGENCE AND LAYER
OMEGA ON LATEST NAM12 RUN INDICATES BEST CHANCE FOR ADDITIONAL
ACCUMULATIONS FOR LOCATIONS GENERALLY SOUTHEAST OF A SHEBOYGAN TO
SILVER LAKE LINE. LOCAL WRF MODELS INDICATE THE BANDS WILL BEGIN
TO AFFECT LAKESHORE LOCALES AFTER 03Z...BEFORE SYSTEM SNOW FROM
CLIPPER HAS ENDED. PROLONGED 6-HOUR FOCUS ON SHEBOYGAN COUNTY
BETWEEN 03Z AND 06Z WILL REQUIRE A LAKE-EEFECT SNOW ADVISORY FOR
THEM. REMAINDER OF LAKE COUNTIES ALREADY IN ADVISORY BUT WILL NEED
TO BE MONITORED AFTER SYSTEM SNOW EXITS FOR POSSIBLE INCLUSION OR
UPGRADE TO WARNING STATUS IF AMOUNTS LOOK TO EXCEED 6 INCHES.

HIGH BUILDS IN FOR THURSDAY...BUT NEXT NRN STREAM WAVE WILL BRING
A TROF AND LIGHT SNOW THURSDAY NIGHT...PUSHING EAST BY FRIDAY MORNING.
ADJUSTED COOLER MAV GUIDANCE FOR TEMPS THRU THE END OF THE WEEK,

.LONG TERM...BOTH GFS AND ECMWF ARE HOLDING ENERGY DIVING INTO THE
BASE OF DEEPENING WEST COAST TROF BACK UNJTIL LATER IN THE
WEEKEND. INITIAL WARM AIR ADVECTION PCPN WILL FALL AS SNOW
SATURDAY...WITH WARMER 850 TEMPS BRINGING A CHANCE FOR A MIX OF
RAINAND SNOW SUNDAY. AFTER INITIAL BARIOCLINIC ZONE NOW EXPECTED
TO SET UP FARTHER SOUTH THAN PREVIOUS RUNS SO WILL CUT BACK AREAL
COVERAGE AND POPS FOR MONDAY.

&&

.AVIATION...EADING EDGE OF IFR CEILINGS AND VISIBILITIES WITH MAIN
SNOW BAND WORKING SOUTHEAST TOWARDS KMSN...WITHIN MID LEVEL
FRONTOGENESIS AREA. TIMING THE LEADING EDGE INTO KMSN BY 21Z TO
22Z...AND INTO KMKE AND KENW BETWEEN 23Z TO 00Z. CEILINGS AND
VISIBILITIES THEN LIKELY TO REMAIN IN IFR CATEGORY UNTIL ABOUT 08Z
WEDNESDAY AT KMSN...GIVEN UPSTREAM CONDITIONS AND STRENGTH OF
EXPECTED UPWARD VERTICAL MOTION FIELDS.

LAKE EFFECT SNOW BANDS EXPECTED TO KEEP IFR CONDITIONS GOING AT KMKE
AND KENW THROUGH WEDNESDAY MORNING. TIGHTENING PRESSURE GRADIENT MAY
ALSO ALLOW FOR SOME GUSTY NORTHEAST WINDS AT KMKE AND KENW ON
WEDNESDAY...SHIFTING NORTH/NORTHWEST IN THE AFTERNOON.

&&

.MARINE...WILL LIKELY ISSUE A SMALL CRAFT ADVISORY FOR NEARSHORE
WATERS FOR WEDNESDAY...WITH GUSTY SURFACE WINDS AND SUBSEQUENT WAVE
ACTION. STEEP LAPSE RATES IN LOW LEVELS SHOULD ALLOW FOR FREQUENT
MIXING OF 25 KNOT WINDS DOWN TO WATER SURFACE.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...SNOW ADVISORY UNTIL 6 AM CST WEDNESDAY FOR WIZ046-047-056>060-
     062>072.

     LAKE EFFECT SNOW ADVISORY FROM 9 PM THIS EVENING TO 9 AM CST
     WEDNESDAY FOR WIZ052.

LM...SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM CST WEDNESDAY FOR
     LMZ643>646.

&&

SHORT/LONG TERM...09
AVIATION/MARINE...08

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
420 PM CST TUE DEC 4 2007

WIZ046-047-051-052-056>060-062>072-051015-
MARQUETTE-GREEN LAKE-FOND DU LAC-SHEBOYGAN-SAUK-COLUMBIA-DODGE-
WASHINGTON-OZAUKEE-IOWA-DANE-JEFFERSON-WAUKESHA-MILWAUKEE-
LAFAYETTE-GREEN-ROCK-WALWORTH-RACINE-KENOSHA-
420 PM CST TUE DEC 4 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST CENTRAL
WISCONSIN...SOUTH CENTRAL WISCONSIN AND SOUTHEAST WISCONSIN.

.DAY ONE...TONIGHT.

A SNOW ADVISORY IS IN EFFECT FOR MOST OF SOUTHERN WISCONSIN FOR THIS
AFTERNOON AND TONIGHT...EXCEPT FOR FOND DU LAC COUNTY. A LAKE EFFECT
SNOW ADVISORY IS IN EFFECT FOR SHEBOYGAN COUNTY. SNOW WILL CONTINUE
TO FALL TONIGHT. SNOW AMOUNTS OF 3 TO 6 INCHES ARE LIKELY BY
WEDNESDAY MORNING OVER MOST OF SOUTHERN WISCONSIN...WITH LIGHTER
TOTALS OVER FOND DU LAC COUNTY.

ON WEDNESDAY MORNING...LAKE EFFECT SNOW SHOWERS MAY DEPOSIT A FEW
MORE INCHES OF SNOW ACROSS AREAS CLOSE TO LAKE MICHIGAN.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED...BUT SNOWFALL MEASUREMENTS
WOULD BE APPRECIATED.

LMZ643>646-051015-
SHEBOYGAN TO PORT WASHINGTON WI-
PORT WASHINGTON TO NORTH POINT LIGHT WI-
NORTH POINT LIGHT TO WIND POINT WI-
WIND POINT WI TO WINTHROP HARBOR IL-
420 PM CST TUE DEC 4 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE MICHIGAN.

.DAY ONE...TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

A SMALL CRAFT ADVISORY IS IN EFFECT FOR WEDNESDAY...FOR NORTHEAST
WINDS OF 15 TO 25 KNOTS...AND WAVES OF 4 TO 7 FEET.

WOOD
WWW.WEATHER.GOV/MKX