FXUS63 KMKX 232241
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
441 PM CST WED DEC 23 2009

FORECAST FOCUS ON HOLIDAY WINTER STORM

.SHORT TERM...

TONIGHT...CONFIDENCE MEDIUM.

HAVE HIGH CONFIDENCE OF PRECIPITATION OCCURRING BUT DILEMMA IS
TYPE. WITH DRY EASTERLY FLOW UNDERCUTTING WARM AIR
ADVECTION...INITIAL PCPN HAS BEEN A LIGHT FREEZING RAIN...SLEET
AND SNOW MIX. EXPECT CHANGE TO A SNOW/SLEET MIX THIS EVENING AS
POCKET OF STRONG OMEGA INTERSECTS SATURATED DENDRITE GROWTH
ZONE...THEN TRANSITION BACK TO FREEZING RAIN OVERNIGHT AS MID
LEVEL WARMING CONTINUES. 

HAVE PLACED SOUTH CENTRAL WISCONSIN UNDER A WINTER STORM WARNING
FOR THE COMBINATION OF 1/4 INCH OR MORE ICE ACCUMULATION AND
SNOW ACCUMULATIONS OF ANYWHERE FROM 1 TO 2 INCHES IN SOUTHERN
SECTIONS TO 3 TO 4 INCHES TO THE NORTH. SOUTHEAST WISCONSIN WILL
BE SLOWER TO SATURATE WITH THAT DRY FLOW AND WILL TRANSITION TO
RAIN BEFORE REACHING 1/4 INCH ICE OR SIGNIFICANT ACCUMULATIONS OF SNOW.

TRAVEL WILL BE HAZARDOUS ACROSS ALL OF SOUTHERN WISCONSIN WITH THE
MIXED PRECIP COMING AT THE BEGINNING OF THE PEAK HOLIDAY TRAVEL PERIOD.

THURSDAY...CONFIDENCE HIGH.

WARM AIR ADVECTION CHANGES PCPN TO ALL RAIN...AND REMAINS ALL RAIN
THROUGH THURSDAY NIGHT. WITH EXPECTED RAINFALL TOTALS AROUND 1
INCH BY FRIDAY MORNING...AND THE SNOW PACK HOLDING 1 TO 1.5 INCHES
OF WATER...ISSUED AN ESF TO HIGHLIGHT FLOOD POTENTIAL IF FORECAST
RAINFALL MATERIALIZES. MAIN CONCERN WILL BE FAST-RESPONDING RIVERS
AND STREAMS...AND THE USUAL LOW-LYING ROADWAYS AND UNDERPASSES
WHICH HAVE THE POTENTIAL TO FILL AS FROZEN GROUND ALLOWS ALL THE
LIQUID TO RUNOFF.

FRIDAY THRU SUNDAY...CONFIDENCE MEDIUM.

AS LOW OCCLUDES...COLD AIR WRAPPING INTO THE SYSTEM WILL ADVECT
OVER THE REGION FROM SOUTHWEST TO NORTHEAST...WITH LIGHT
PRECIPITATION CHANGING BACK TO ALL SNOW. HIGH TEMPERATURES WILL BE
AROUND 6 AM...THEN STEADY OR SLOWLY FALL THROUGH THE MORNING. WITH
MAIN PCPN PUSH ALREADY THROUGH...ONLY EXPECT LIGHT ACCUMULATIONS.
SCATTERED SNOW SHOWERS EXPECTED THROUGH THE DAY SATURDAY INTO
SUNDAY UNTIL UPPER LOW . NO REAL BLAST OF ARCTIC AIR...BUT EXPECT
HIGHS IN THE LOW TO MID 20S AND LOWS IN THE TEENS.
 

.LONG TERM...MONDAY THROUGH WEDNESDAY.

GFS BRUSHES THE NORTHERN CWA WITH A SHORT WAVE MONDAY...BUT
PREFER THE MORE NORTHERN TRACK OF THE ECMWF. RIDGING KEEPS REGION
DRY INTO WEDNESDAY. NEXT CHANCE OF PRECIPITATION COMES WEDNESDAY
NIGHT AND THURSDAY. WITH RIDGING...PREFERRED THE COOLER MAV TEMPS
WITH THE SINGLE DIGITS TO LOW TEENS AT NIGHT AND THE LOWER 20S
DURING THE DAY.

&&

.AVIATION...COMPLICATED FORECAST FOR THIS PERIOD. MVFR CEILINGS AND 
VISIBILITIES WITH ANY LINGERING FREEZING RAIN OR DRIZZLE SHOULD 
CHANGE OVER TO SNOW BY 00Z TO 01Z THURSDAY...AS AIR COLUMN 
SATURATES. STRONG LIFT EXPECTED BEYOND 00Z THURSDAY...AS THE STRONG 
SURFACE LOW MOVES NORTHEAST INTO THE REGION. BRISK AND GUSTY EAST 
WINDS WILL CONTINUE THROUGH THURSDAY.

EXPECT IFR CEILINGS AND VISIBILITIES WITH THE SNOW ACROSS TAF SITES 
THROUGH MOST OF THE EVENING...BEFORE MIXING WITH SLEET FROM 04Z TO 
05Z THURSDAY. THE SLEET SHOULD MIX WITH LIGHT FREEZING RAIN AFTER 
06Z THURSDAY...BEFORE BECOMING PREVAILING LIGHT FREEZING RAIN BY THE 
12Z TO 15Z THURSDAY PERIOD. WARMER AIR CONTINUING TO MOVE INTO THE 
AREA WILL CHANGE THE PRECIPITATION TO ALL RAIN BY 15Z TO 18Z 
THURSDAY ACROSS THE TAF SITES. 

&&

.MARINE...SMALL CRAFT ADVISORY CONTINUES UNTIL 18Z THURSDAY...WITH A 
GALE WARNING CONTINUING FROM 18Z THURSDAY THROUGH 18Z FRIDAY. STRONG 
SURFACE PRESSURE GRADIENT WILL CONTINUE TO GET TIGHTER ACROSS THE 
NEARSHORE WATERS THROUGH FRIDAY. 

BRISK EAST WINDS TO 30 KNOTS TONIGHT AND EARLY THURSDAY WILL 
INCREASE TO 35 KNOT GALES AND VEER SOUTHEAST BY AFTERNOON...AS GOOD 
MIXING OF STRONGER WINDS FROM 1000 FEET ABOVE GROUND LEVEL COMMENCE. 
SOUTHEAST GALES UP TO 40 KNOTS ARE EXPECTED THURSDAY NIGHT. HIGH 
WAVES OF 8 TO 12 FEET ARE EXPECTED BY THURSDAY NIGHT INTO 
FRIDAY...WITH THE PERSISTENT ONSHORE FLOW. WINDS WILL SHIFT SOUTH BY 
LATER ON FRIDAY...AS THE STRONG SURFACE LOW MOVES INTO THE REGION. 

A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED FRIDAY AFTERNOON AND 
FRIDAY NIGHT...AS THE BRISK WINDS AND HIGH WAVES SLOWLY SUBSIDE.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER STORM WARNING UNTIL NOON CST THURSDAY FOR WIZ056-057-062-
     063-067>069.

     WINTER WEATHER ADVISORY UNTIL NOON CST THURSDAY FOR WIZ058-
     064>066-070>072.

     WINTER WEATHER ADVISORY UNTIL NOON CST THURSDAY FOR WIZ051-052-
     059-060.

     WINTER STORM WARNING UNTIL NOON CST THURSDAY FOR WIZ046-047.

LM...SMALL CRAFT ADVISORY UNTIL NOON CST THURSDAY FOR LMZ643>646.

     GALE WARNING FROM NOON THURSDAY TO NOON CST FRIDAY FOR 
     LMZ643>646.

&&

$$

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