FXUS63 KARX 240954
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
354 AM CST THU DEC 24 2009
.SHORT TERM...TODAY THROUGH SATURDAY
THE MAIN FORECAST CONCERN WITH THIS PACKAGE REMAINS THE VARYING
PRECIPITATION TYPES WITH THIS WINTER STORM FROM TODAY THROUGH AT
LEAST FRIDAY.
AT 3 AM...A STRENGTHENING SURFACE LOW WAS DEVELOPING ACROSS
EASTERN TEXAS. AN ELONGATED INVERTED TROUGH EXTENDED NORTHWARD
FROM THIS LOW NORTHWARD TO LAKE WINNE PEG. WITH THE LOSS OF ICE
CRYSTALS ACROSS MUCH OF THE FORECAST AREA EARLY THIS MORNING...THE
PRECIPITATION HAS BEEN MAINLY LIQUID OVERNIGHT. IN MANY LOCATIONS
THE TEMPERATURES ARE NEAR OR BELOW FREEZING...SO THIS
PRECIPITATION IS THE FORM OF FREEZING RAIN OR FREEZING DRIZZLE.
HERE AT THE OFFICE...WE ESTIMATE THAT WE HAVE RECEIVED ABOUT A
TENTH OF AN INCH OF ICE. EVEN THOUGH MANY OF THE AIRPORTS ACROSS
NORTHEAST IOWA AND SOUTHWEST WISCONSIN ARE REPORTING TEMPERATURES
ABOVE FREEZING...THERE IS SOME CONCERN THAT THERE STILL COULD BE
SOME FREEZING RAIN OR FREEZING DRIZZLE OCCURRING IN THE COLDER AND
SHELTERED RIVER VALLEYS AND COULEES.
BOTH THE 24.00Z MODELS INDICATE THAT A TONGUE OF 2 TO 3C AIR HAS
MOVED INTO WESTERN WISCONSIN AND THE ADJACENT COUNTIES ALONG THE
MISSISSIPPI IN SOUTHEAST MINNESOTA AND NORTHEAST IOWA THIS
MORNING. AS THE LIFT ENHANCES ACROSS THE AREA LATER THIS MORNING
AND AFTERNOON AHEAD OF AN APPROACHING SHORT WAVE AND THE DRY
EASTERLY FLOW HELPS TO ENHANCE THE EVAPORATIVE COOLING...THIS WARM
AIR SHOULD COOL ACROSS THIS AREA. IT IS THIS EVAPORATIVE COOLING
WHICH WHICH MAY PREVENT THE TEMPERATURES ALONG AND NORTH OF THE
INTERSTATE 90 CORRIDOR FROM WARMING TOO MUCH TODAY. AS A
RESULT...A WINTRY MIX WAS KEPT IN THESE AREAS TODAY.
IN SOUTHWEST WISCONSIN AND NORTHEAST IOWA...CONFIDENCE IS A BIT
HIGHER THAT THIS AREA MAY JUST BE RAIN TODAY. THERE WAS SOME
DISCUSSION ABOUT DROPPING THE WINTER STORM WARNING BRIEFLY...BUT
WITH TERRAIN IN THAT AREA...WE CANNOT BE 100 PERCENT THAT SOME OF
COULEES AND VALLEYS WILL WARM ENOUGH NOT TO SEE SOME FREEZING
RAIN...BUT THIS IS TOO SMALL SCALE TO DEPICT IN THE GRIDS. IN
ADDITION...WE ARE QUITE CERTAIN FREEZING RAIN AND SNOW WILL BE THE
GENERAL WEATHER TONIGHT...SO DO NOT SEE THE POINT OF DROPPING
WARNING FOR TODAY ONLY TO MOST LIKELY HAVE IT GO BACK IN EFFECT
TONIGHT.
MEANWHILE ACROSS THE REMAINDER OF SOUTHEAST MINNESOTA AND
NORTHEAST IOWA TODAY...IT APPEARS THAT THE ATMOSPHERIC COLUMN WILL
COOL SUFFICIENTLY ENOUGH THAT THE PRECIPITATION WILL CHANGE OVER
TO PREDOMINANTLY SNOW BY LATE THIS MORNING AND CONTINUE INTO THIS
AFTERNOON. WITH THIS SAID...THERE STILL COULD BE TIMES WHERE WE
MAY LOSE THE ICE CRYSTALS FOR THE FEEDER/SEEDER MECHANISM...SO A
MENTION OF FREEZING RAIN WAS LEFT IN THE GRIDS.
FOR TONIGHT...THE ENTIRE AREA SHOULD COOL SUFFICIENTLY THAT THE
PRECIPITATION ACROSS THE FORECAST AREA SHOULD BE ALL SNOW. HOWEVER
WITH THIS SAID...THERE STILL MAY BE A BIT OF FREEZING RAIN ACROSS
WESTERN WISCONSIN THIS EVENING IF THE COLUMN DOES NOT COOL FAST ENOUGH.
ON FRIDAY...A TONGUE OF SLIGHTLY WARMER AND DRIER AIR MOVES INTO
SOUTHWEST AND CENTRAL WISCONSIN DURING THE MORNING. THE BUFKIT AND
MODEL SOUNDINGS IN THIS REGION SUGGEST THAT WE MAY ONCE AGAIN
LOSE OUR ICE CRYSTALS. AS A RESULT...SOME FREEZING RAIN WAS ADDED
ALONG WITH THE SNOW IN THESE AREAS. DURING THE LATE MORNING AND
AFTERNOON THIS WARMER TOUNGUE SLIDES NORTHWEST ACROSS THE
REMAINDER OF THE AREA...BUT IT IS PROGRESSIVELY COOLING...SO JUST
WENT WITH SNOW IN THE AFTERNOON. TO SHOW JUST HOW WOUND UP THIS
LOW PRESSURE AREA IS...THE COLDEST AIR IS ADVECTING INTO OUR AREA
FROM THE SOUTHEAST.
ADDITIONAL SNOW TOTALS THROUGH FRIDAY...LOOK TO BE 10 TO 15 INCHES
WEST OF A BLACK RIVER FALLS WISCONSIN TO NEW HAMPTON IOWA
LINE...AND 5 TO 10 INCHES EAST OF THE AFOREMENTIONED LINE. ADDITIONAL
ICE ACCUMULATIONS OF ONE TO TWO TENTHS LOOK POSSIBLE...MAINLY FOR
TODAY...FROM DECORAH IOWA NORTHEAST INTO LA CROSSE AND BLACK RIVER
FALLS.
.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY
THE 24.00Z MODELS CONTINUE TO SHOW THAT THE VERTICALLY STACKED LOW
PRESSURE SYSTEM WILL BE STILL LOCATED ACROSS THE FORECAST AREA ON
SATURDAY NIGHT. AS A RESULT...THE SNOW CHANCES WERE INCREASED A
BIT MORE. IF THIS TREND CONTINUES...WE MAY HAVE TO INCREASE THESE
SNOW CHANCES A BIT MORE YET. EVEN THOUGH THE SNOW CHANCES ARE
LIKELY...ADDITIONAL SNOW AMOUNTS SHOULD BE ON THE LIGHT SIDE
/GENERALLY LESS THAN A HALF INCH/.
ON SUNDAY...IT STILL LOOKS LIKE THE LOW PRESSURE AREA WILL BE
MOVING AWAY FROM THE REGION. HOWEVER IT APPEARS THAT IT WILL BE
CLOSE ENOUGH TO PRODUCE ENOUGH CYCLONIC FLOW ACROSS THE REGION
THAT THERE WILL LIKELY BE SOME LIGHT SNOW. DUE TO THIS...THE SNOW
CHANCES WERE RAISED BY ABOUT 10 PERCENT INTO THE 25 TO 35 PERCENT
RANGE. THE HIGHEST SNOW CHANCES WILL BE ACROSS WESTERN WISCONSIN.
AT THIS TIME...IT LOOKS LIKE SNOW AMOUNTS WOULD LIKELY RANGE FROM
A TRACE TO A TENTH OF AN INCH.
&&
.AVIATION...TODAY AND TONIGHT
LITTLE IN THE WAY OF IMPROVEMENT IS EXPECTED ON THURSDAY FOR WEATHER
CONDITIONS ACROSS THE REGION...IN FACT...THEY WILL LIKELY WORSEN AS
THE SURFACE LOW CURRENTLY OVER EASTERN TEXAS LIFTS NORTH INTO IOWA
AND DRAWS MOISTURE FROM THE GULF ALONG WITH IT.
PRECIPITATION TYPE AND TIMING WILL BE THE TOUGHEST PART OF THIS TAF
CYCLE AS LOW LEVEL TEMPERATURES LINGER RIGHT AROUND FREEZING
THROUGHOUT MOST OF THE DAY. THIS MEANS THAT THERE LIKELY WILL BE
PERIODS OF FREEZING RAIN...SLEET...SNOW...AND RAIN THAT OCCUR OVER
THE NEXT 24 HOURS. THE PREDOMINANT PRECIP TYPE THIS MORNING APPEARS
TO BE SLEET AND FREEZING RAIN...BUT AS SURFACE TEMPERATURES INCREASE
A FEW DEGREES DURING THE DAY...MAY SEE BETTER CHANCES FOR SLEET AND
RAIN...PARTICULARLY AT LSE WHERE THE WARMER AIR WOULD BE AT.
GOING INTO THIS EVENING...LOW TO MID LEVEL TEMPERATURES COOL OFF
ENOUGH TO WHERE IT APPEARS THAT THE PRECIPITATION WILL FLIP BACK TO
BEING MAINLY SNOW. THIS TREND SHOULD CONTINUE THROUGH THE REST OF
FRIDAY AS MORE COLDER AIR CONTINUES TO WRAP INTO THE REGION.
CIGS WILL CONTINUE TO REMAIN LOW AT LSE/RST THROUGHOUT THE PERIOD
AND WILL LIKELY DROP TODAY AS LOW LEVEL MOISTURE INCREASES WITH THE
LOW MOVING NORTH. VIS WILL ALSO LIKELY DROP THIS EVENING AND
OVERNIGHT AS THE PRECIPITATION CHANGES OVER FROM THE MIX TO SNOW.
WINDS WILL CONTINUE TO BE OUT OF THE EAST AND GUSTY AT TIMES.
EXPECT MVFR TO IFR CONDITIONS TO PERSIST OR WORSEN THROUGH THE TAF
PERIOD.
&&
.HYDROLOGY...TODAY
WITH BETWEEN A HALF AND ONE INCH OF LIQUID PRECIPITATION ACROSS
SOUTHWEST WISCONSIN AND PARTS OF NORTHEAST IOWA TODAY...THERE IS
SOME CONCERN THAT THIS MAY CAUSE SOME RISES IN AREA RIVERS. THIS
TYPICALLY WOULD NOT BE A PROBLEM...BUT THESE RIVERS ARE ICE
COVERED AND THESE RISES MAY RESULT IN SOME ICE JAMS WHICH COULD
RESULT IN SOME LOCALIZED FLOODING.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...WINTER STORM WARNING UNTIL 6 PM CST FRIDAY FOR WIZ017-WIZ029-
WIZ032-WIZ033-WIZ034-WIZ041-WIZ042-WIZ043-WIZ044-WIZ053-
WIZ054-WIZ055-WIZ061.
MN...WINTER STORM WARNING UNTIL 6 PM CST FRIDAY FOR MNZ079-MNZ086-
MNZ087-MNZ088-MNZ094-MNZ095-MNZ096.
IA...WINTER STORM WARNING UNTIL 6 PM CST FRIDAY FOR IAZ008-IAZ009-
IAZ010-IAZ011-IAZ018-IAZ019-IAZ029-IAZ030.
&&
$$
SHORT/LONG TERM...BOYNE
AVIATION...HALBACH
