Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 240930
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
330 AM CST SAT JAN 24 2015

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 330 AM CST SAT JAN 24 2015

THE MAIN FOCUS FOR THIS WEEKEND COMES WITH THE SNOW EXPECTED
TONIGHT INTO SUNDAY MORNING.

CURRENTLY...NORTHWEST FLOW IS IN PLACE ALOFT WITH A SHORT WAVE
TROUGH IN THE PACIFIC NORTHWEST RIDING THE NORTHERN FRINGES OF A
WESTERN CONUS RIDGE. AT THE SURFACE...A RELATIVELY MILD AIR MASS
IS IN PLACE FROM WEST TO NORTHWEST FLOW ACROSS THE UPPER
MISSISSIPPI RIVER VALLEY. A COLD FRONT STRETCHES FROM A LOW NEAR
THE SOUTHEAST PART OF HUDSON BAY DOWN TOWARD INTERNATIONAL FALLS
AND THEN TRANSITIONS TO A WARM FRONT WHICH LEADS INTO ANOTHER LOW
IN CENTRAL ALBERTA. ANOTHER MILD DAY IS ON TAP WITH THE SEASONALLY
WARM AIR MASS BEING ADVECTED EAST ACROSS THE NORTHERN PLAINS AHEAD
OF THE UPSTREAM SURFACE LOW.

THE TRENDS FOR TONIGHTS SYSTEM CONTINUE TO FAVOR A MORE SOUTHWEST
TRACK OF THE SURFACE LOW/MID LEVEL TROUGH. WHAT STARTS OUT AS A
MAINLY OPEN MID LEVEL TROUGH IN THE DAKOTAS ENDS UP DEEPENING AND
CLOSING OFF OVER IOWA BY SUNDAY MORNING. THIS LEADS TO THE SNOW
BANDS GOING FROM BEING FAIRLY LIGHT FOR MUCH OF THE NIGHT TO BEING
FAIRLY INTENSE AS THE LOW CLOSES. HOWEVER...TRENDS FROM THE
24.00Z MODEL SUITE SUGGEST THAT THESE HEAVIER BANDS MAY TRACK TO
THE SOUTH OF NORTHEAST IOWA. OF NOTE IS THE 24.00Z NSSL WRF
REFLECTIVITY WHICH BRINGS LIGHT SNOW IN FROM THE WEST THIS
EVENING AND STRENGTHENS A BAND FROM NORTH CENTRAL TO EASTERN IOWA
TOWARD DAYBREAK. THIS SOUTHWESTWARD TRACK ALSO MEANS THAT THE SNOW
ENDS QUICKER ON SUNDAY MORNING FROM NORTH TO SOUTH AS THE
LOW/TROUGH SWINGS INTO CENTRAL ILLINOIS. NOT MUCH OF A DENDRITIC
GROWTH ZONE BUT LIFT IS FAIRLY DEEP/STRONG FROM THE SURFACE/UPPER
LEVEL LOW THAT PROPAGATES THROUGH. BASED ON THIS AND COBB DATA
FROM THE NAM/GFS...WENT WITH SNOW RATIOS OF AROUND 12-14:1
OVERNIGHT WITH AROUND A QUARTER OF AN INCH OF QPF FALLING IN
NORTHEAST IOWA WITH LESSER AMOUNTS TO THE NORTH AND EAST. THIS
GENERALLY BRINGS THE 2-4 INCH SNOW BAND TO BEING MORE LIKELY FROM
SOUTH CENTRAL MINNESOTA INTO NORTHEAST IOWA.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 330 AM CST SAT JAN 24 2015

THE NEXT CHANCES FOR PRECIPITATION COMES IN EARLY ON MONDAY AND
LINGERS THROUGH EARLY TUESDAY MORNING AS A SURFACE/LOW LEVEL
TROUGH/WARM FRONT MOVES THROUGH THE REGION. THIS SYSTEM DOES NOT
LOOK LIKE IT WILL HAVE SIGNIFICANT AMOUNTS OF PRECIPITATION WITH
IT...BUT DOES POSE A CHALLENGE FOR WHAT THE TYPE WILL BE.
CURRENTLY JUST HAVE SNOW MENTIONED...BUT THERE ARE SOME
INDICATIONS...ESPECIALLY ALONG AND WEST OF THE MISSISSIPPI
RIVER...THAT ICE IS LOST IN THE COLUMN AND THAT DRIZZLE/FREEZING
DRIZZLE COULD OCCUR. CONFIDENCE IN THIS OUTCOME IS FAIRLY LOW
RIGHT NOW...BUT IS A TREND THAT WILL HAVE TO BE MONITORED.

OTHERWISE...WEDNESDAY IS STILL LOOKING LIKE IT WILL BE THE WARMEST
DAY OF THE WEEK THOUGH THERE ARE DIFFERING SOLUTIONS WITH HOW
WARM. THE 24.00Z GEM IS THE WARMEST WITH BRINGING TEMPERATURES
INTO THE UPPER 40S...WHICH IS UNLIKELY...WHILE THE GFS IS THE
COOLEST WITH KEEPING THE WARM FRONT SOUTH OF THE REGION. THE
24.00Z ECMWF DID NOT SWAY MUCH FROM ITS PREVIOUS RUNS...SO TRENDED
CLOSER TO THAT WITH THIS SETUP.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1048 PM CST FRI JAN 23 2015

STRATUS...OR REALLY LACK THEREOF...CONTINUES TO REMAIN A PROBLEM
FOR THE AVIATION FORECAST. MVFR/VFR STRATUS DECK MOVING AWAY FROM
THE TAF SITES AT THE MOMENT...THOUGH MORE MVFR STRATUS LURKS
UPSTREAM OVER NORTHWEST WI INTO NORTHEAST MN. WITH THE FLOW JUST
ABOVE THE GROUND TURNING NORTHWESTERLY...ITS POSSIBLE SOME OF THIS
MVFR STRATUS COULD BRIEFLY GET INTO LSE BETWEEN 11-13Z...BEFORE
THE FLOW TURNS BACK TO THE WEST TO PUSH IT OUT. OTHERWISE...VFR
CONDITIONS ARE EXPECTED AT BOTH TAF SITES THROUGH THE DAY AS DRY
AIR CONTINUES TO BE BROUGHT IN FROM THE DAKOTAS. DURING THE
EVENING...A LOW PRESSURE SYSTEM WILL TRACK FROM SOUTH DAKOTA INTO
IOWA...SPREADING SNOW TOWARDS THE TAF SITES. FOR NOW JUST BROUGHT
VISIBILITIES DOWN TO MVFR AROUND 03Z IN THE SNOW...SINCE IT
APPEARS THE HEAVIER SNOW SHOULD STAY TO THE SOUTHWEST. THE LOW
LEVEL WIND FLOW LOOKS TO TURN TO THE EAST-NORTHEAST DUE TO THE
SYSTEMS TRACK...WHICH WILL HELP PULL THE STRATUS THAT GETS STUCK
ALONG/NORTH OF I-94 TODAY INTO THE TAF SITES. BROUGHT CEILINGS
DOWN TO MVFR FOR NOW.


&&

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

$$

SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION...AJ


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