Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 160929
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
429 AM CDT THU OCT 16 2014

.UPDATE...
ISSUED AT 429 AM CDT THU OCT 16 2014

AREAS OF DENSE FOG HAVE FORMED ALONG AND EAST OF THE MISSISSIPPI
RIVER EARLY THIS MORNING. THE WORST CONDITIONS WERE REPORTED OVER
CENTRAL WISCONSIN WHERE LOCAL LAW ENFORCEMENT HAS REPORTED THAT
DRIVING OVER 35 MPH IS DIFFICULT. THE INTERSTATE 90 AND 94
CORRIDOR IS BEING IMPACTED BY THIS DENSE FOG SO THOSE TRAVELING
OVER THESE AREAS SHOULD BE PREPARED FOR DENSE FOG AND NEAR ZERO
VISIBILITY AT TIMES. FURTHER TO THE WEST THE FOG WAS MAINLY
CONFINED TO VALLEY LOCATIONS. A DENSE FOG ADVISORY HAS BEEN ISSUED
FOR COUNTIES BORDERING THE MISSISSIPPI RIVER EXTENDING THROUGH
CENTRAL INTO NORTH CENTRAL WISCONSIN THROUGH 10 AM THIS MORNING.
THE VISIBILITY WILL START TO IMPROVE AFTER 9 AM THIS MORNING AS
MIXING INCREASES.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 351 AM CDT THU OCT 16 2014

MAIN FORECAST CONCERNS ARE ON AREAS OF DENSE FOG THIS MORNING ALONG
AND EAST OF THE MISSISSIPPI RIVER. FOCUS THEN TURNS TO
TEMPERATURES/DEWPOINTS THIS AFTERNOON.

HIGH PRESSURE OVERHEAD EARLY THIS MORNING AND MOSTLY CLEAR SKIES
HAVE RESULTED IN AREAS OF DENSE FOG ALONG AND EAST OF THE
MISSISSIPPI RIVER. LOW PRESSURE CONTINUES TO SLIDE EAST OF THE
REGION TODAY AS A WEAK COLD FRONT APPROACHES FROM THE NORTHERN
PLAINS. AHEAD OF THE FRONT...A WARMER AIRMASS MOVES IN WITH 925 MB
TEMPERATURES WARMING INTO THE 13C TO 17C RANGE. THE WARMEST 925
MB AIR WILL MOVE INTO AREAS ALONG AND WEST OF THE MISSISSIPPI
RIVER LATE THIS AFTERNOON INTO EARLY THIS EVENING. MIXING AHEAD OF
THE FRONT THIS AFTERNOON SHOULD HELP BOOST TEMPERATURES INTO THE
UPPER 60S TO AROUND 70 OVER MUCH OF SOUTHEAST  MINNESOTA AND
NORTHEAST IOWA. IN ADDITION...THIS MIXING WILL BRING DRIER AIR TO
THE SURFACE AND SOME GUSTY WINDS DURING THE AFTERNOON HOURS.
FORECAST MODELS ADVECT DEWPOINTS OF 45-50 AHEAD OF THE FRONT THIS
AFTERNOON WITH THE SOURCE REGION BEING WESTERN IOWA/MISSOURI. NOT
BUYING INTO THESE HIGHER DEWPOINTS GIVEN THE LACK OF
EVAPOTRANSPIRATION  WITH THE CURED GRASSES AND CROPS OVER THE
FORECAST AREA. DECIDED TO LOWER DEWPOINTS WITH MIXING EXPECTED TO
REACH TO AROUND 900 MB. WE SHOULD SEE AFTERNOON RELATIVE HUMIDITY
VALUES DROP TO AROUND 30 PERCENT THIS AFTERNOON OVER PORTIONS OF
NORTHEAST IOWA AND SOUTHEAST MINNESOTA. SOME CLOUD COVER WILL
LINGER OVER PORTIONS OF WESTERN WISCONSIN THANKS TO WEAK IMPULSES
ROTATING AROUND THE DEPARTING LOW. THESE CLOUDS WILL EVENTUALLY
CLEAR OUT AS WE GO INTO THE AFTERNOON HOURS. THE FRONT WILL SLIDE
ACROSS THE REGION TONIGHT AS LOW PRESSURE DROPS SOUTHEAST  OUT OF
NORTH DAKOTA/NORTHERN MINNESOTA. PLAN ON MOSTLY CLEAR TO PARTLY
CLOUDY SKIES TONIGHT WITH LOWS FALLING INTO THE 40S.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 351 AM CDT THU OCT 16 2014

THE LOW SLIDES ACROSS NORTHERN WISCONSIN/UPPER MICHIGAN ON FRIDAY
SWINGING A TROUGH THROUGH THE FORECAST AREA. THIS WILL SPREAD
SHOWERS INTO THE FORECAST AREA. THE HIGHEST CHANCES FOR THIS
ACTIVITY WILL  BE OVER NORTHCENTRAL WISCONSIN...CLOSE TO THE LOW.
THE CLOUD COVER AND COOLER AIR MOVING IN WILL KEEP HIGH
TEMPERATURES IN THE 50S ON FRIDAY. BREEZY NORTHWEST WINDS WILL
ALSO BE IN PLACE LEADING TO AN OVERALL COOL AUTUMN DAY. PLAN ON
NORTHWEST WINDS OF 15 TO 20 MPH WITH GUSTS APPROACHING 35 MPH IN
OPEN AREAS. THE TROUGH EXITS THE AREA FRIDAY NIGHT WITH HIGH
PRESSURE BUILDING IN ITS WAKE. COOL AND DRY CONDITIONS ARE
EXPECTED ON SATURDAY WITH HIGHS EXPECTED TO BE IN THE UPPER 40S TO
LOWER 50S. WILL HAVE TO KEEP AN EYE OUT FOR FOG POTENTIAL SATURDAY
NIGHT INTO SUNDAY MORNING WITH THE HIGH OVERHEAD. FORECAST
SOUNDINGS ARE VERY DRY AN EVEN SUGGEST THERE COULD BE HIGH CLOUDS
OVERHEAD. WILL HOLD OFF ON PLACING FOG IN THE FORECAST BUT IT WILL
BE SOMETHING TO WATCH CLOSELY. ANOTHER TROUGH SWINGS THROUGH THE
REGION ON SUNDAY AND COULD BRING A FEW RAIN SHOWERS TO THE AREA.
THE ECMWF IS THE ONLY MODEL SHOWING RAIN OVER MUCH OF THE FORECAST
AREA WHILE THE GFS AND CANADIAN ARE DRY. HAVE INCLUDED A SLIGHT
CHANCE OF SHOWERS OVER PORTIONS OF NORTH CENTRAL INTO CENTRAL
WISCONSIN. THE TROUGH EXITS SUNDAY NIGHT. HIGH PRESSURE RETURNS
EARLY NEXT WEEK WITH DRY AND QUIET WEATHER EXPECTED.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 945 PM CDT WED OCT 15 2014

VALLEY FOG BECOMING MORE LIKELY...AS LONG AS THAT CLOUD SHIELD STAYS
TO THE EAST. BACK EDGE CURRENTLY SETS UP FROM AROUND BLACK RIVER
FALLS TO PRAIRIE DU CHIEN WI...WHILE HIGH PRESSURE TO THE WEST IS
KEEPING THOSE AREAS CLEAR. T/TD SPREAD FROM 00Z WAS ONLY 10 DEGREES
AT KLSE...WITH CALM SFC WINDS. BOTH VERY FAVORABLY FOR 1/4SM FG.
RAP/NAM/HRRR BUFKIT SOUNDINGS SHOW A DEEP LIGHT WIND LAYER UPWARDS
OF 4 KFT. ALSO FAVORABLE. ALL THE ELEMENTS ARE THERE...EXCEPT FOR
GUARANTEED CLEAR SKIES. IF THE CLOUDS CONTINUE TO INCH EAST THIS
EVENING LIKE SOME MODELS SUGGEST...FG IS MORE LIKELY. IF IT SLOSHES
IN AND OUT...POTENTIALLY BUILDING WESTWARD OVERNIGHT...THE FOG
THREAT IS MUCH LESS. DIFFICULT QUESTION TO ANSWER...BUT SATELLITE
TRENDS HINTING THAT THE CLOUDS MIGHT STAY AT BAY. GOING TO LOWER
VSBYS AT KLSE AS A RESULT...WITH ADJUSTMENTS MADE AS NEEDED.

AS FOR KRST...MORE MIXING TODAY AND NOT MUCH REBOUND TONIGHT IN TDS
KEEPING T/TD SPREAD LARGE THROUGH MID EVENING. THIS IS GOING TO KEEP
THE THREAT FOR MVFR BR DOWN...DESPITE A FAVORABLE LIGHT WIND LAYER.

WEAK HIGH PRESSURE WILL BE THE MAIN WEATHER INFLUENCE THU...WITH AN
UPPER LEVEL SHORTWAVE TROUGH DIPPING ACROSS NORTHERN PORTIONS OF
MN/WI LATE THU NIGHT/FRI. CURRENTLY...MODELS KEEP MOST OF THE
ASSOCIATED PCPN WITH THIS FEATURES NORTH OF THE TAF SITES...AND IN
THE FRI-FRI NIGHT TIME FRAME. SHOULD SEE AN INCREASE IN CLOUDS
OVERNIGHT THU THOUGH...WITH MVFR/IFR CIGS LIKELY FRIDAY.


&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR WIZ017-029-
     032>034-041>043-053>055-061.

MN...DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR MNZ079-088-
     096.

IA...DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR IAZ011-030.

&&

$$

UPDATE...WETENKAMP
SHORT TERM...WETENKAMP
LONG TERM...WETENKAMP
AVIATION.....RIECK



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