Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KARX 211735
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1135 AM CST SUN DEC 21 2014

.UPDATE...
ISSUED AT 1135 AM CST SUN DEC 21 2014

WARM FRONT CONTINUES TO PUSH NORTH AND WITH THAT VISIBILITIES HAVE
BEEN IMPROVING AS WELL. HAVE CLEARED DENSE FOG ADVISORY FROM AREA
WITH LITTLE IMPACT EXPECTED REST OF DAY.

MEANWHILE NORTH OF INTERSTATE 94 UPGLIDE OVER FRONT WILL LEAD TO
FURTHER ENHANCEMENT OF LIGHT PRECIPITATION TODAY. NO WARM LAYER
ALOFT WILL MEAN FAIRLY DISTINCT RAIN-SNOW LINE AND OBSERVATIONS SEEM
TO REFLECT THAT. SHORT TERM GUIDANCE ALL SUGGESTS PRECIPITATION
EXPANDING IN THAT AREA AS WELL SO WOULD NOT BE SURPRISED WITH MINOR
ACCUMULATIONS...ESPECIALLY NORTH OF HIGHWAY 29 IN WISCONSIN.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CST SUN DEC 21 2014

THE MAIN FOCUS IS WITH THE DENSE FOG THIS MORNING ALONG WITH THE
DEVELOPING PRECIPITATION TODAY INTO TONIGHT.

DENSE FOG HAS FORMED ALONG AND NORTH OF A WARM FRONT THAT EXTENDS
EAST FROM THE SIOUX FALLS AREA ALONG THE IOWA/MINNESOTA BORDER
THEN RUNS SOUTHEAST INTO NORTHERN ILLINOIS. OBSERVATIONS IN
NORTHEAST IOWA ARE STILL SHOWING 1/4SM...SO PLAN TO LET THE
ADVISORY CONTINUE THROUGH THE MORNING OR UNTIL CONDITIONS IMPROVE.
THE 21.06Z HRRR/RAP SHOW THIS WARM FRONT ADVANCING NORTHWARD THIS
MORNING WITH THE BAND OF LOWEST VISIBILITIES ALSO LIFTING NORTH
AND DIMINISHING AS THE MORNING GOES ON. WILL HAVE TO KEEP AN EYE
ON OBS THROUGH THE MORNING FOR WHETHER THE ADVISORY CAN BE EXPIRED
EARLY.

GOING INTO THIS AFTERNOON...THERE HAS BEEN A FAIRLY CONSISTENT
MESSAGE OF PRECIPITATION DEVELOPING AS A 700MB TROUGH CATCHES UP
TO THE LOW LEVEL WARM AIR ADVECTION. THE HIGHEST CHANCES FOR THIS
PRECIPITATION CONTINUES TO BE ACROSS NORTHERN WISCONSIN WHERE THE
LIFT/MOISTURE WILL BE DEEPEST. THERMAL PROFILES LOOK COLD ENOUGH
TO SUPPORT ALL SNOW AT LEAST INITIALLY BEFORE THE WARM SECTOR
LIFTS NORTH TONIGHT. WITH ABOUT A TENTH OF AN INCH OF QPF AND SNOW
RATIOS AROUND 8:1 OR SO...AM EXPECTING A QUICK INCH OF SNOW IN
CLARK/TAYLOR COUNTIES THIS AFTERNOON WITH AREAS TO THE SOUTH
LIKELY SEEING MORE OF A DRIZZLE/RAIN SITUATION.

THE MAIN QUESTION WITH THIS PRECIPITATION IS WITH A DRY LAYER THAT
SHOWS UP ON 21.00Z NAM/GFS/RAP SOUNDINGS AROUND 800-700MB AND
WHETHER THAT COLUMN WILL BE SMALL ENOUGH FOR SEEDER-FEEDER TO
WORK. ALSO...SURFACE TEMPERATURES WILL BE ABOVE FREEZING...SO THIS
COMBINED WITH HOW DRY THE COLUMN IS LEADS TO SOME QUESTIONS WITH
PRECIPITATION TYPE. WITH FORCING RELATIVELY WEAK...EXPECT THAT THE
DRY LAYER WILL BE DEEP ENOUGH TO KEEP PRECIPITATION MORE AS
RAIN/DRIZZLE...PARTICULARLY WITH THE ABOVE FREEZING NEAR SURFACE
LAYER.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 330 AM CST SUN DEC 21 2014

FAIRLY GOOD CONSENSUS AMONGST THE GUIDANCE WITH BRINGING THE MAIN
BAND OF PRECIPITATION THROUGH ON MONDAY INTO MONDAY EVENING AS THE
CLOSED MID LEVEL LOW APPROACHES AND A LEAD SHORTWAVE TROUGH LIFTS
NORTHWARD AHEAD OF IT. HAVE MAINLY GONE WITH RAIN AS THE
PRECIPITATION TYPE FOR MONDAY...BUT CONFIDENCE IS NOT VERY HIGH
WITH THIS AS FORECAST SOUNDINGS FROM THE 21.00Z NAM/GFS ONLY SHOW
THE WARM LAYER GETTING TO 1 TO 2C ABOVE FREEZING...IF THAT. 21.03Z
SREF PROBABILITIES SHOW MAINLY RAIN WITH THE EXCEPTION OF NORTHERN
WISCONSIN. IF IT IS NOT ALL RAIN...COULD BE SOME SLEET OR SNOW
THAT MIXES IN THERE AS WELL.

AFTER THE INITIAL BAND MOVES THROUGH BY MONDAY EVENING...THE
NAM/GFS SHOW THE DRY SLOW MOVING IN WHILE THE ECMWF SHOWS A
HEAVIER BAND OF RAIN/SNOW DEVELOPING NORTH OF A SURFACE LOW
TRACKING TO THE NORTH ALONG THE MISSISSIPPI. THE ECMWF THEN
DEVELOPS A DEEPER SURFACE LOW BY TUESDAY AFTERNOON COMPARED TO THE
NAM/GFS. SHOULD THE ECMWF SOLUTION BE THE TREND...WILL HAVE TO
PUSH PRECIPITATION CHANCES/AMOUNTS UP MORE THAN WHAT THEY
CURRENTLY ARE AT.

THE NEXT FEATURE OF NOTE IS WITH A PHASING MID LEVEL TROUGH THAT
LOOKS LIKE IT WILL BRING A BAND OF LIGHT SNOW IN ON THURSDAY
EVENING INTO FRIDAY MORNING. COULD SEE AN INCH OR TWO OF
ACCUMULATION FROM THIS SYSTEM WITH THE 21.00Z GFS/ECMWF NOT TOO
FAR OFF FROM EACH OTHER.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1135 AM CST SUN DEC 21 2014

POOR AVIATION WEATHER TO CONTINUE WITH FAIRLY WIDESPREAD IFR
THROUGHOUT THE REGION. ALTHOUGH VISIBILITIES DID IMPROVE AS WARM
FRONT LIFTED NORTH...LOW CEILINGS AND INTERMITTENT LIGHT
PRECIPITATION WILL CONTINUE INTO MONDAY. TEMPERATURE PROFILE IS
CLOSE TO RAIN-SNOW LINE BUT BANKING ON CONDITIONS REMAINING WARM
ENOUGH NEAR GROUND LEVEL FOR MAINLY RAIN SO WILL NOT INTRODUCE MIX
AT TAF SITES YET. IF STEADIER RAIN DEVELOPS TONIGHT AS FORCING
INCREASES AHEAD OF SYSTEM...VISIBILITIES COULD IMPROVE AFTER SOME
DECREASE EARLY THIS EVENING BUT THAT WILL TAKE A LOT OF SHORT TERM
TWEEKING.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
 WI...NONE.
 MN...NONE.
 IA...NONE.

&&

$$

UPDATE...SHEA
SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION...SHEA


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.