Winter Storm in Wisconsin, December 18 to 19, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
302 PM CST THU DEC 18 2008

.DISCUSSION...FORECAST FOCUS ON MAJOR WINTER STORM TONIGHT AND
FRIDAY...THEN ON A ANOTHER SYSTEM SATURDAY NIGHT/SUNDAY WITH
BITTERLY COLD TEMPERATURES TO FOLLOW.

.TONIGHT AND FRIDAY...

THE FORECAST EMPHASIS IS BY FAR ON THE SYSTEM TO HAMMER THE AREA
TONIGHT AND FRIDAY. EVERYTHING SEEMS TO BE ON TRACK FROM PREVIOUS
FORECASTS...EXCEPT FOR A SLIGHTLY LATER ARRIVAL TIME. MODELS
CONTINUE TO SLOW THE ONSET OF SNOW FROM EARLY THIS EVENING TO
LATER THIS EVENING. THIS IS NOT ALL THAT SURPRISING...MODELS
USUALLY TREND SLOWER RATHER THAN FASTER WITH WINTER STORMS.
ALREADY PUSHED BACK THE START TIME OF THE WINTER STORM WARNING TO
03Z IN AREAS SOUTHWEST OF A LINE FROM THE DELLS TO BELOIT...AND
06Z TO AREAS NORTHEAST OF THIS LINE. THE EVENING SHIFT WILL
ADDRESS TIMING ISSUES A LITTLE BETTER AND MAY TWEAK THE HEADLINES
AGAIN SLIGHTLY. THE SNOW WILL BEGIN VERY QUICKLY LATE THIS EVENING
AS THE ATMOSPHERE SATURATES. COULD BE SEEING VISIBILITIES DROP FROM
10 MILES TO LESS THAN 1/2 MILE WITHIN AN HOUR. ONCE THIS
OCCURS...CONDITIONS WILL DETERIORATE VERY QUICKLY.

EVERYTHING IS LINING UP FOR A REAL NICE WINTER STORM. THIS
COLORADO LOW WILL TRACK FROM SOUTHEAST COLORADO THROUGH
MISSOURI...CENTRAL ILLINOIS...AND CENTRAL INDIANA. LOADS OF
MOISTURE SOUTH OF THIS TRACK HAS BEEN PRODUCING WIDESPREAD DENSE
FOG ACROSS THE LOWER MISSISSIPPI RIVER VALLEY WITH DEW POINTS
APPROACHING 70 NEAR THE GULF COAST. THIS MOISTURE WILL BE
TRANSPORTED NORTH VERY QUICKLY ON A DEVELOPING 70+ KT 850 MB JET
AND WILL BE LIFTED INTO A DEVELOPING TROWAL OVER SOUTHERN
WISCONSIN LATE TONIGHT. MIXING RATIOS WILL RANGE FROM AROUND 2.5
G/KG ACROSS THE NORTHERN CWA TO AROUND 3.5 G/KG NEAR THE ILLINOIS
BORDER. MODELS SHOW STRONGER LIFT TODAY THAN THEY DID YESTERDAY
WITH 30 TO 40 UNITS OF OMEGA...100-200 J/KG OF ELEVATED
CAPE...STRONG FRONTOGENESIS...AND WEAK STATIC STABILITY WITH SOME
FOLDING OF THE ISENTROPES IN THE DENDRITIC GROWTH REGION. THUNDER
CERTAINLY LOOKS LIKE A GOOD POSSIBILITY...SO WILL CONTINUE THE
SCHC OF THUNDERSTORMS ACROSS THE SRN HALF OF THE CWA.

QPF ON THE NAM HAS BEEN STEADILY INCREASING WITH TIME AND NOW
SHOWS 1-1.25 INCHES ACROSS MUCH OF THE AREA. THIS IS IN STARK
CONTRAST TO WHAT THE 18Z RUN WAS SHOWING YESTERDAY WITH LESS THAN
0.25 INCHES. THE GFS AND ECMWF ARE SLIGHTLY LESS WITH BETWEEN 0.65
INCH OVER MARQUETTE COUNTY...TO NEARLY 1.0 INCH NEAR KENOSHA.
MODELS HAVE A BETTER GRASP OF MOISTURE NOW THAT THE MAIN SYSTEM IS
BEING SAMPLED WELL BY RAOBS.

OVERALL...WILL BE GOING WITH AROUND 8 INCHES ACROSS THE FAR NORTH
WITH 10 TO 13 INCHES NEAR THE ILLINOIS BORDER...USING A 11:1 OR
12:1 RATIO. THIS AGREES WELL WITH THE GRACIA METHOD WHICH YIELDS 8
INCHES ACROSS THE FAR NORTH TO 12 OR 13 INCHES NEAR THE ILLINOIS
BORDER. LOCALIZED AREAS COULD RECEIVE MORE IF THE DEFORMATION BAND
SITS OVER AN AREA FOR A WHILE...OR UNDER ANY THUNDERSTORMS THAT
DEVELOP. CONVECTION WILL BE THE WILD CARD. IF CONVECTION
OCCURS...SNOW RATES OF 2 TO 3 INCHES PER HOUR WOULD BE LIKELY.

NOTE...IT IS IMPORTANT TO REALIZE ONE SHOULDN/T ADD THE RANGE OF
SNOW TOTALS SHOWN ON THE POINT AND CLICK MAP FOR EACH PERIOD. A
SPECIFIC POINT IS NOT LIKELY TO BE ON THE HIGH END OF THE RANGE
FOR EACH PERIOD.

THE HEAVIEST SNOW SHOULD OCCUR BETWEEN 09Z AND 15Z. THE SNOW WILL
QUICKLY TAPER OFF AFTER 17Z...EXCEPT FOR SOME LAKE EFFECT
LINGERING OVER THE EAST THROUGH AFTERNOON.

.FRIDAY NIGHT AND SATURDAY...

LIGHT LAKE EFFECT SNOW IS LIKELY TO CONTINUE FRIDAY NIGHT INTO
SATURDAY WITH ONLY AN INCH OR TWO EXPECTED. TEMPERATURES WON/T BE
EXCEPTIONALLY COLD DUE TO AN EASTERLY FLOW OFF LAKE MICHIGAN.

.SATURDAY NIGHT AND SUNDAY...

THE NEXT SYSTEM WILL ORGANIZE FROM TWO DISTURBANCES...ONE BEING A
CLIPPER SYSTEM AND ANOTHER BEING A WEAK GULF LOW. THESE TWO
SYSTEMS WILL PHASE OVER THE GREAT LAKES TO PRODUCE THE NEXT ROUND
OF SNOW. THIS SYSTEM WILL NEED TO BE WATCHED CLOSELY AS IT HAS
POTENTIAL TO BRING ANOTHER MAJOR STORM...ESPECIALLY TO THE
NORTHEAST CWA. QPF IS HIGHEST THERE AS DRIER AIR BEGINS WRAPPING
INTO THE SYSTEM FROM THE SOUTHWEST. QPF VALUES OF BETWEEN 1/3 AND
1/2 INCH ARE CURRENTLY PROGGED...BUT THESE MAY INCREASE IF
MOISTURE CAN SUFFICIENTLY MAKE IT THIS FAR NORTH AFTER THE PASSAGE
OF THE SYSTEM FOR TONIGHT. HAVE A GENERAL 4 TO 7 INCHES...WITH THE
LOWER AMOUNTS SOUTHWEST AND THE HIGHER AMOUNTS NORTHEAST. WINDS
WILL BE QUITE STRONG WITH THIS SYSTEM AND SNOW RATIOS ARE EXPECTED
TO BE QUITE HIGH GRANTED THICKNESSES AROUND 510. CONSIDERABLE
BLOWING AND DRIFTING SNOW LOOKS PROBABLE...AND DESPITE LOWER SNOW
TOTALS...WINTER STORM WATCHES MAY BECOME NECESSARY LATER TO
ADDRESS THE SNOW AND BLOWING SNOW.

.SUNDAY NIGHT AND MONDAY...

SKIES CLEAR RAPIDLY SUNDAY NIGHT AS A POCKET OF COLD AIR DRIFTS
RIGHT OVER WISCONSIN. 2 METER TEMPERATURES ON THE GFS RANGE FROM
-10 TO -15F WITH SLIGHTLY WARMER TEMPS ON THE ECMWF SUNDAY NIGHT.
500 MB HEIGHTS FALL TO AROUND 513 DAM. USING A STRONG INVERSION FROM
925MB...WHERE TEMPERATURES ARE AROUND -19C...LOWS COULD EASILY
DROP INTO THE TEENS BELOW ZERO IN MANY LOCATIONS. MEX GUIDANCE HAS
TRENDED IN THIS DIRECTION...BUT NOT NEARLY FAR ENOUGH. AFTER BEING
BURNED ON LOW TEMPERATURES OVER THE PAST COUPLE OF SHIFTS...EVEN
AFTER UNDERCUTTING MOS BY SEVERAL DEGREES...I FEEL I SHOULD LEAN
TOWARD THE 2 METER TEMPS. GUSTY WINDS BEHIND THE STRONG OCCLUDED
LOW OVER THE LAKES MAY CAUSE WIND CHILLS TO DROP TO NEAR WIND
CHILL WARNING CRITERIA /-35F/ FOR A PERIOD OF SEVERAL HOURS SUNDAY
NIGHT.

CONTINUED CAA INTO MONDAY MORNING WILL RESULT IN A BITTER COLD DAY
WITH HIGHS PROBABLY REMAINING BELOW ZERO.

.MONDAY NIGHT THROUGH NEXT THURSDAY...

WAA BEGINS MONDAY NIGHT WITH RISING TEMPERATURES AHEAD OF ANOTHER
SYSTEM FOR TUESDAY. WILL CONTINUE A CHANCE OF SNOW TUESDAY AND
TUESDAY EVENING. THE REST OF THE PERIOD LOOKS DRY AND COLD.

&&

.AVIATION...VFR ACROSS THE AREA THROUGH ABOUT 03Z FRIDAY. HIGH
CLOUDS WILL DRIFT ACROSS THE AREA...AHEAD OF MAJOR STORM SYSTEM
DEVELOPING OVER THE CENTRAL PLAINS. MOISTURE SURGES INTO THE AREA
FROM THE SOUTHWEST AFTER 00Z WITH CIGS AND VSBYS LOWERING RAPIDLY AS
SNOW MOVES IN.  THE SURFACE LOW WILL TRACK INTO CENTRAL ILLINOIS BY
AROUND 12Z FRIDAY.  THE SNOW WILL START VERY ABRUPTLY. EXPECT IFR
CONDITIONS AFT 03Z FRIDAY AND POSSIBLY LIFR IN HEAVY SNOW AT TIMES
FROM 06Z THROUGH 17Z FRIDAY. LIGHT SNOW MAY LINGER ALONG THE
LAKESHORE AS NORTHEASTERLY WINDS FUNNEL IN SOME LAKE EFFECT SNOW
SHOWERS BEHIND THE SYSTEM.

&&

.MARINE...A STRONG LOW PRESSURE SYSTEM WILL TRACK FROM NEBRASKA
THROUGH ILLINOIS AND OHIO TONIGHT THROUGH FRIDAY AFTERNOON...
REMAINING TO THE SOUTH OF SOUTHERN WISCONSIN. THIS PATTERN WILL
PRODUCE STRONG EASTERLY WINDS OVER SOUTHEAST WISCONSIN. MODELS SHOW
35 KNOT WINDS UP TO 2000 FEET AROUND 14Z...WHICH HAS POTENTIAL TO MIX
DOWN TO THE SURFACE. SO...SFC WINDS SHOULD BE SUSTAINED TO AROUND 20
KNOTS...WITH FREQUENT GUSTS TO 30 KNOTS...FROM TONIGHT THROUGH FRI
MORNING. A FEW GALE FORCE GUSTS TO 35 KNOTS MAY BE POSSIBLE. WAVES
WILL BUILD TO OVER 8 FEET. THOUGH WINDS WILL DIMINISH...THEY WILL
REMAIN ELEVATED. WITH A FAVORABLE FETCH FOR CONTINUED HIGH
WAVES...WAVES ARE NOT EXPECTED TO FALL BACK BELOW SMALL CRAFT
ADVISORY LEVELS THROUGH SATURDAY.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER STORM WARNING FROM 9 PM THIS EVENING TO 12 PM CST FRIDAY
     FOR WIZ056-062-063-067>069.

     WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 3 PM CST FRIDAY
     FOR WIZ046-047-051-052-057>060-064>066-070>072.

LM...SMALL CRAFT ADVISORY FROM 2 AM FRIDAY TO 6 AM CST SATURDAY FOR
     LMZ643>646.

&&

SHORT/LONG TERM...18 BORGHOFF
AVIATION/MARINE...13 MRC

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
405 PM CST THU DEC 18 2008

WIZ046-047-051-052-056>060-062>072-191000-
MARQUETTE-GREEN LAKE-FOND DU LAC-SHEBOYGAN-SAUK-COLUMBIA-DODGE-
WASHINGTON-OZAUKEE-IOWA-DANE-JEFFERSON-WAUKESHA-MILWAUKEE-
LAFAYETTE-GREEN-ROCK-WALWORTH-RACINE-KENOSHA-
405 PM CST THU DEC 18 2008

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

.DAY ONE...TONIGHT

A MAJOR WINTER STORM WILL HIT THE AREA TONIGHT THROUGH FRIDAY
MORNING. THE SNOW SHOULD BEGIN DURING THE MID EVENING HOURS WEST OF
MADISON BUT WILL LIKELY HOLD OFF UNTIL AFTER MIDNIGHT IN THE
MILWAUKEE AREA. SNOW ACCUMULATIONS OF 7 TO 11 INCHES ARE EXPECTED
NORTH OF A LINE FROM MADISON TO MILWAUKEE...AND 9 TO 13 INCHES SOUTH
OF THAT LINE. THE SNOW WILL TAPER OFF LATER FRIDAY MORNING. BRISK
EASTERLY WINDS WILL PRODUCE BLOWING AND DRIFTING SNOW.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

ANOTHER EVENT WITH 3 TO 5 INCHES OF SNOW ACCUMULATION IS POSSIBLE
SATURDAY NIGHT THROUGH SUNDAY NIGHT. DANGEROUS WIND CHILLS ARE
POSSIBLE SUNDAY NIGHT...AS WELL. THE THIRD ROUND OF SNOW COULD
ARRIVE LATE MONDAY NIGHT AND CONTINUE THROUGH TUESDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

SNOWFALL REPORTS WILL BE APPRECIATED.

LMZ643>646-191000-
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-
405 PM CST THU DEC 18 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE MICHIGAN.

.DAY ONE...TONIGHT

A SMALL CRAFT ADVISORY IS IN EFFECT LATE TONIGHT THROUGH FRIDAY
NIGHT...DUE TO BRISK EASTERLY WINDS ASSOCIATED WITH A LOW PRESSURE
SYSTEM PASSING SOUTH OF THE AREA.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A SMALL CRAFT ADVISORY WILL BE NEEDED AGAIN SATURDAY NIGHT
THROUGH TUESDAY.

MRC
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