FXUS63 KARX 230958
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
358 AM CST WED DEC 23 2009
.SHORT TERM...TODAY THROUGH CHRISTMAS DAY
THE MAJOR WINTER STORM CONTINUES TO BE THE MAIN CONCERN FOR THIS
TIME PERIOD.
AT 3 AM...BOTH THE DOPPLER RADARS AND SURFACE OBSERVATIONS WERE
INDICATING THAT BAND OF FREEZING DRIZZLE CONTINUES TO MOVE
NORTHWARD INTO NORTHEAST IOWA AND SOUTHWEST WISCONSIN.
OCCASIONALLY THIS DRIZZLE WILL MAKE IT UP INTO THE INTERSTATE 90
CORRIDOR...BUT THIS PRECIPITATION HAS BEEN FAIRLY SPOTTY DUE TO
THE DRY EASTERLY FLOW.
THE 23.00Z MODELS CONTINUE TO SHOW THAT LIGHT PRECIPITATION WILL
CONTINUE TO MOVE NORTHWARD INTO THE AREAS ALONG AND SOUTH OF THE
INTERSTATE 90 CORRIDOR THROUGH AT LEAST 3 PM TODAY. WITH THE BEST
MOISTURE TRANSPORT AND FRONTOGENESIS LOCATED ACROSS NORTHEAST IOWA
AND SOUTHWEST WISCONSIN...THE PRECIPITATION CHANCES WERE THE
HIGHEST IN THESE AREAS AND RAPIDLY DECLINED TO THE NORTH. WITH THE
LIGHT ICE ACCUMULATIONS LIKELY TO CONTINUE ACROSS NORTHEAST IOWA
AND SOUTHWEST WISCONSIN THROUGH EARLY AFTERNOON...THE END TIME OF
THE FREEZING RAIN ADVISORY WAS EXTENDED FROM NOON TO 3 PM.
FROM LATE AFTERNOON THROUGH EARLY OVERNIGHT HOURS OF THURSDAY...A
SHORT WAVE TROUGH WILL BE MOVING NORTH THROUGH THE FORECAST AREA.
THIS WILL LIKELY ENHANCE THE LIFT ACROSS THE REGION AND ALSO
INTRODUCED THE ICE CRYSTAL NEEDED TO SEED THE SATURATED LOW LEVEL
MOISTURE. AS A RESULT...WE SHOULD SEE A RAPID CHANGE OVER FROM
FREEZING RAIN OR FREEZING DRIZZLE TO SNOW. AS THIS WAVE MOVES
AWAY...IT LOOKS LIKE MUCH OF THE FORECAST AREA MAY SHIFT BACK TO
FREEZING DRIZZLE AND FREEZING RAIN. THIS WILL BE ESPECIALLY THE
CASE ACROSS NORTHEAST IOWA AND SOUTHWEST WISCONSIN.
ANOTHER SHORT WAVE TROUGH WILL MOVE NORTHWARD ACROSS AREA ON
THURSDAY. THIS SYSTEM WILL LIKELY BRING THE ICE CRYSTALS NEEDED
FOR THE SEEDER FEEDER MECHANISM TO GENERATE ANOTHER ROUND OF
ACCUMULATING SNOW ACROSS THE REGION.
ON THURSDAY NIGHT...STRONG CYCLOGENESIS WILL LIKELY OCCUR ACROSS
IOWA. IN ADDITION...THE SURFACE LOW WILL MOVE WEST. THIS INITIALLY
LOOKS STRANGE...BUT THIS IS DUE TO ANOTHER NORTHERN STREAM SYSTEM
MERGING WITH THE SOUTHERN STREAM SYSTEM. THIS ULTIMATELY RESULTS
IN THE DEVELOPMENT OF A CLOSED 500 MB LOW. THE MODELS CONTINUE TO
SHOW THAT THE SOUTHERN SYSTEM WILL BRING ABUNDANT GULF OF MEXICO
MOISTURE NORTHWARD INTO THE REGION. PRECIPITABLE WATER VALUES ARE
OVER 200 PERCENT OF NORMAL. THERE SHOULD BE ENOUGH ICE CRYSTALS
AROUND FOR MUCH OF THE PRECIPITATION TO BE IN THE FORM OF SNOW.
HOWEVER THERE CONTINUES TO BE SOME HINTS THAT THE TEMPERATURES MAY
WARM ENOUGH ALOFT THAT THE PRECIPITATION ACROSS SOUTHWEST AND
CENTRAL WISCONSIN MAY TRANSITION OVER TO RAIN AND THIS MAY LINGER
INTO FRIDAY.
ON FRIDAY MORNING...IT APPEARS THAT MUCH OF THE AREA MAY LOSE THE
ICE CRYSTALS REQUIRED FOR SNOW. THIS IS DUE TO A TONGUE OF DRIER
AIR WRAPPING INTO THE SYSTEM. THIS MAY RESULT IN THE PRECIPITATION
TRANSITIONING OVER TO FREEZING DRIZZLE OR FREEZING RAIN. HOWEVER
THIS LOOKS TO BE SHORT LIVED...BECAUSE STRONG COLD AIR ADVECTION
FROM THE SOUTHWEST WILL BRING A RETURN TO THE ICE CRYSTALS ON
FRIDAY AFTERNOON AND THE PRECIPITATION SHOULD ONCE AGAIN
TRANSITION BACK TO SNOW.
WITH THE PRECIPITATION TRANSITIONING BACK AND FORTH FROM SNOW TO
FREEZING RAIN...THE TOTAL SNOW AND ICE ACCUMULATIONS ARE STILL
VERY TRICKY. HOWEVER IT DOES LOOK POSSIBLE THAT AREAS NORTHWEST OF
A LINE FROM CHARLES CITY IOWA TO ARCADIA WISCONSIN MAY SEE
ANYWHERE FROM 12 TO 18 INCHES OF SNOW. THESE TOTALS THEN DECREASE
TO 5 TO 8 INCHES ACROSS CENTRAL WISCONSIN AND SOUTHWEST WISCONSIN.
ICE ACCUMULATIONS OF A TENTH TO TWO TENTHS OF AN INCH LOOK
POSSIBLE ALONG AND SOUTH OF INTERSTATE 90.
.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY
MUCH OF THE TIME THIS MORNING HAS BEEN SPENT ON THE IMPENDING
WINTER STORM...SO THESE TIME PERIODS WERE JUST GIVEN A CURSORY
GLANCE.
THE 23.00Z MODELS...LIKE THEIR PREDECESSORS...CONTINUE TO SHOW
THAT THE UPPER LEVEL LOW WILL STILL BE LINGERING ACROSS THE
FORECAST AREA THIS WEEKEND. DUE TO THIS...THE SNOW CHANCES WERE
INCREASED SOME ON BOTH FRIDAY NIGHT AND SATURDAY. IN ADDITION...
THE SNOW CHANCES LOOK LIKE THEY MAY NEED TO BE RAISED ON SATURDAY
NIGHT AND ADDED TO SUNDAY.
IN ADDITION WITH ABUNDANT CLOUDS LINGERING ACROSS THE REGION AND A
DELAY IN THE ARCTIC AIR INTRUSION...THE TEMPERATURES LOOK LIKE
THEY MAY BE A BIT TOO COOL. WITH STILL UNCERTAINTY IN THESE
PERIODS...AN IMPENDING WINTER STORMS...AND ALREADY WELL
COLLABORATED GRIDS...NO CHANGES WERE MADE TO THESE GRIDS.
&&
.AVIATION...TODAY AND TONIGHT
WEATHER CONCERNS CONTINUE TO FOCUS ON THE FREEZING DRIZZLE CHANCES
ALONG WITH LOWERING CIGS/VIS THIS AFTERNOON AHEAD OF A POTENT STORM
SYSTEM THAT IS EXPECTED TO BRING A MIX OF SNOW AND FREEZING RAIN
TONIGHT.
LITTLE IN THE WAY OF CURRENT ACTIVITY OF FZDZ DESPITE THE FORECAST
SOUNDINGS LOOKING FAVORABLE FOR ITS DEVELOPMENT WITH MOIST LOW LEVEL
RELATIVE HUMIDITY AND DRY UPPER LEVELS OF THE ATMOSPHERE THANKS TO
AN UPPER LEVEL RIDGE. MAIN MISSING ELEMENT AT THIS POINT IS SOME
STRONGER LOW LEVEL FORCING IN THIS MOIST LAYER. SOME RETURNS HAVE
BEEN NOTED ON RADAR FURTHER SOUTH NEAR DVN...BUT EXPECT THESE AREAS
OF FZRA/DZ TO HAVE A TOUGH TIME MAKING IT TO LSE WITH RST HAVING A
BETTER SHOT. FOR THE TIME BEING...WILL LEAVE THE TAF DRY THROUGH
THE REST OF THE MORNING.
CIGS/VIS HAVE BEEN BULLISH WITH THE MAIN CORE OF IFR CIGS EXTENDING
FROM EASTERN IOWA NORTHWEST INTO SOUTHWEST MINNESOTA WITH A BATCH OF
MVFR CIGS EXTENDING EAST OF THIS AREA. EXPECTING THAT THERE WONT BE
MUCH CHANGE IN THIS GRADIENT UNTIL THIS AFTERNOON AS THE POTENT
STORM SYSTEM BEGINS TO STRENGTHEN ACROSS THE SOUTHERN PLAINS. THIS
WILL LEAD TO AN INTENSIFYING OF SOUTHERLY LOW LEVEL WINDS THAT WILL
AID IN TRANSPORTING GULF MOISTURE UP INTO THE REGION. CIGS WILL
LIKELY DROP TO IFR OR WORSE RATHER QUICKLY AS THIS OCCURS.
IN TERMS OF PRECIPITATION...LOOKS AS THOUGH AFTER THE CHANCES FOR
FZDZ PERIOD END THIS AFTERNOON...WILL HAVE A PERIOD OF SNOW THIS
EVENING WITH A TRANSITION TO FREEZING RAIN. WILL HAVE TO KEEP A TAB
ON THE LOW LEVEL TEMPERATURE PROFILE OVERNIGHT AND WHETHER ANY SLEET
MAY MIX IN...BUT AT THIS POINT THEY DO NOT LOOK WARM ENOUGH TO CAUSE
ANY IP.
WINDS WILL ALSO BE STRENGTHENING OUT OF THE EAST THIS AFTERNOON WITH
SOME SUSTAINED WINDS AROUND 20KT AND HIGHER GUSTS UP TO 30KT
POSSIBLE.
EXPECT MVFR CONDITIONS TO DROP TO IFR THIS AFTERNOON WITH LIFR/VLIFR
NOT OUT OF THE QUESTION AS THE PRECIPITATION STARTS TONIGHT.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR WIZ054-
WIZ055-WIZ061.
WINTER STORM WARNING FROM 3 PM THIS AFTERNOON TO 6 PM CST FRIDAY
FOR WIZ054-WIZ055-WIZ061.
WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST FRIDAY
FOR WIZ041-WIZ042-WIZ043-WIZ044-WIZ053.
WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 PM CST FRIDAY
FOR WIZ017-WIZ029-WIZ032-WIZ033-WIZ034.
MN...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST FRIDAY
FOR MNZ086-MNZ087-MNZ088-MNZ094-MNZ095-MNZ096.
WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 PM CST FRIDAY
FOR MNZ079.
IA...FREEZING RAIN ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR IAZ008-
IAZ009-IAZ010-IAZ011-IAZ018-IAZ019-IAZ029-IAZ030.
WINTER STORM WARNING FROM 3 PM THIS AFTERNOON TO 6 PM CST FRIDAY
FOR IAZ008-IAZ009-IAZ010-IAZ011-IAZ018-IAZ019-IAZ029-IAZ030.
&&
$$
SHORT/LONG TERM...BOYNE
AVIATION...HALBACH
