Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 221758
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1158 AM CST SAT NOV 22 2014

.UPDATE...
ISSUED AT 1157 AM CST SAT NOV 22 2014

CONTINUE TO MONITOR FOR IMPROVEMENT OF DENSE FOG AROUND THE
ADVISORY AREA. STILL HAVE MANY OBSERVATIONS OF LESS THAN 1/4SM
AROUND NERN IA INTO SWRN WI. SHERIFFS SAY MINIMAL IMPROVEMENT AS
WELL. CURRENTLY HAVE THE DENSE FOG ADVISORY UNTIL 2 PM SOUTH OF
INTERSTATE 90...AND PROLONGED MOISTURE FEED AND SNOW PACK ARE
DOING NOTHING BUT PROMOTING FOG. NO REAL AIR MASS CHANGE IS
EXPECTED...ALTHOUGH OVERNIGHT WE DO SURGE MORE MOISTURE AND WARMTH
INTO THE AREA FOR SNOW PACK REMOVAL...BOUNDARY LAYER
SATURATION...AND MORE FOG LIKELY. IN FACT...TONIGHT WE ARE HEADING
TOWARD A WIDESPREAD DENSE FOG EVENT IT APPEARS. WILL COLLABORATE
AND MAKE THE FINAL DECISIONS AROUND MID-AFTERNOON ON THE OVERNIGHT
AND INTO SUNDAY DENSE FOG.

HAVE ALSO RECEIVED 22.12Z MODEL FORECAST GUIDANCE AND THE 24.09Z
SREF...AND THERE IS A LOWER PROBABILITY...BUT NOW PRESENT...NEAR
BLIZZARD FORECAST SUNDAY NIGHT AND MONDAY THAT COULD AFFECT
WISCONSIN. THE 24.12Z CANADIAN GLOBAL AND NCEP GFS HAVE
ACCUMULATING SNOW BACK WEST TO ROCHESTER MN TO THE WEST AND
SOUTHWEST OF THE SURFACE LOW /OVER LAKE MICHIGAN/. WE ARE WAITING
ON THE 24.12Z ECMWF AS ITS HIGHEST SKILL SCORES AND SOLUTIONS
WEIGH HEAVILY IN OUR DECISIONS FOR ACTION. ACTION FOR THIS CHANGE
IN THE FORECAST WOULD RANGE FROM RAISING THE POSSIBILITY OF THIS
OUTCOME SUNDAY NIGHT AND MONDAY IN OUR MESSAGING...TO ISSUING A
WINTER STORM WATCH FOR SOME. THIS DECISION WILL COME IN THE NEXT
HOURS.
&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 251 AM CST SAT NOV 22 2014

CHALLENGES INCLUDE PRECIP TYPE/CHANCES/AMOUNTS THROUGH MONDAY AS A
STRONG LOW PRESSURE SYSTEM MOVES ACROSS THE UPPER MIDWEST. 22.00Z
GLOBAL MODELS INITIALIZED WELL AND ARE IN GOOD AGREEMENT THROUGH
AT LEAST 25.00Z (MONDAY NIGHT)...DIVERGING A BIT THEREAFTER IN
TIMING AND STRENGTH OF SHORT-WAVES IN NORTHWEST FLOW ALOFT.

22.09Z WATER VAPOR LOOP SHOWS A STRONG WAVE CRASHING ON THE PACIFIC
NORTHWEST SHORE AND THIS FEATURE WILL BE THE PRIMARY PLAYER FOR
THE NEXT FEW DAYS. LIGHT DRIZZLE/FREEZING DRIZZLE EARLY THIS MORNING
WILL DISSIPATE AND PUSH EAST AS THE DEEPEST MOISTURE MOVES INTO IL
AND SOUTHEAST WI. WILL KEEP 20 POPS ACROSS THE EASTERN HALF OF THE
FORECAST AREA TODAY FOR ANY LINGERING DRIZZLE...BUT ADDITIONAL
ACCUMULATION WILL BE A HUNDREDTH OR TWO AT BEST. OTHERWISE...TODAY
WILL BE MOSTLY CLOUDY AND WARM WITHIN THE WARM AIR ADVECTION
REGIME AS THE +10 C 850 HPA ISOTHERM APPROACHES THE FORECAST AREA
BY 23.00Z. AFTERNOON HIGHS WILL CLIMB INTO THE UPPER 30S TO MID
40S.

FOR TONIGHT...A STRONG WARM FRONT WILL SURGE NORTHWARD WITH THE
NEXT SLUG OF MOISTURE IN ITS WAKE. SATURATION ONLY EXPECTED TO
AROUND 2 KM OVERNIGHT WITH DRY AIR ALOFT...SO ANY PRECIP WILL
LIKELY STILL BE IN THE FORM OF DRIZZLE. TEMPERATURES BY THEN WILL
BE WELL ABOVE ZERO SO FREEZING WILL NOT BE AN ISSUE. THE BIGGER
CONCERN WILL BE WIDESPREAD FOG WITH THE 22.03Z SREF SHOWING A 100
PERCENT PROBABILITY THAT VISIBILITY WILL DROP BELOW 1 MILE
TONIGHT. THERE IS A CHANCE A DENSE FOG ADVISORY WILL BE NEEDED...
BUT WILL WAIT UNTIL CURRENT FREEZING RAIN ADVISORY HAS EXPIRED
AND/OR CANCELLED BEFORE MAKING ANY DECISIONS.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 251 AM CST SAT NOV 22 2014

ATMOSPHERIC COLUMN SATURATES TO AT LEAST 500 HPA BY SUNDAY
RESULTING IN DRIZZLE CHANGING OVER TO RAIN. STRONG FORCING/LIFT
FROM THE SURFACE TO 850 HPA ALONG AND AHEAD OF AN APPROACHING COLD
FRONT WILL RESULT IN WIDESPREAD RAIN THROUGH THE DAY. STILL SOME
UNCERTAINTY AS TO WHERE THE WESTERN EDGE OF THE PRECIP SHIELD WILL
SET-UP...BUT AT THIS TIME APPEARS TO BE NEAR A LINE FROM HUDSON WI
TO MASON CITY IA. RAINFALL AMOUNTS SUNDAY WILL GENERALLY RANGE
FROM OVER A HALF INCH ACROSS THE SOUTHEAST TO AROUND A TENTH
ACROSS THE NORTHWEST.

COLD FRONT WILL SWING ACROSS THE FORECAST AREA SUNDAY NIGHT
RESULTING IN A GRADUAL CHANGE OVER FROM RAIN TO SNOW. DEFORMATION
AXIS SNOW BAND WILL ROTATE AROUND THE BACKSIDE OF THE DEPARTING
LOW ON MONDAY GENERALLY RESULTING IN 1 TO 3 INCHES OF SNOW WITH
THE HIGHER AMOUNTS FURTHER NORTH AND EAST. NORTHWEST WIND WILL
ALSO INCREASE WITH GUSTS AS HIGH AS 30 MPH ACROSS PORTIONS OF
SOUTHEAST MN AND NORTHEAST IA...POSSIBLY CREATING SOME BLOWING AND
DRIFTING SNOW.

TUESDAY THROUGH FRIDAY WILL SEE A RETURN OF A SUB-FREEZING AIR
MASS WITH TEMPERATURES GENERALLY IN THE 20S DURING THE DAY AND
TEENS AT NIGHT. THE NEXT BEST CHANCE FOR LIGHT SNOW WILL BE
TUESDAY NIGHT THROUGH WEDNESDAY AS THE NEXT SHORT-WAVE DROPS SOUTH
IN NORTHWEST FLOW ALOFT. THANKSGIVING DAY INTO THE HOLIDAY WEEKEND
SHOULD BE DRY...BUT COLD AS SURFACE HIGH PRESSURE BUILDS ACROSS
THE NATION/S MID-SECTION.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1155 AM CST SAT NOV 22 2014

BIG PICTURE OF THIS FORECAST CYCLE FOR THE TAFS WAS ABUNDANT
MOISTURE AND SOUTHERLY WARM FLOW IN THE LOW LEVELS WILL PROMOTE
AN IFR FORECAST THROUGHOUT THE PERIOD. IT IS QUITE LIKELY WE WILL
SEE EXTENDED LIFR CONDITIONS IN THE OVERNIGHT AND MORNING SUNDAY.
WE WILL LIKLEY SEE IFR CONDITIONS THROUGH COLD FRONT PASSAGE TIME
WHICH WILL COME SUNDAY NIGHT. HOWEVER...SHOULD SNOW OCCUR...IFR
CONDITIONS ARE EXPECTED SUNDAY NIGHT INTO MONDAY.
&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...DENSE FOG ADVISORY UNTIL 2 PM CST THIS AFTERNOON FOR WIZ053>055-
     061.

MN...DENSE FOG ADVISORY UNTIL 2 PM CST THIS AFTERNOON FOR MNZ094>096.

IA...DENSE FOG ADVISORY UNTIL 2 PM CST THIS AFTERNOON FOR IAZ008>011-
     018-019-029-030.

&&

$$

UPDATE...BAUMGARDT
SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION...BAUMGARDT


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