Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 240435
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1135 PM CDT MON MAR 23 2015

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 311 PM CDT MON MAR 23 2015

WATER VAPOR SATELLITE THIS AFTERNOON SHOWS A SHORT WAVE TROUGH
OVER NORTHERN NEVADA AND ANOTHER OFF THE PACIFIC NORTHWEST COAST.
THE 23.12Z MODELS CONTINUE TO TREND STRONGER WITH THE SHORT WAVE
TROUGH OVER NEVADA ONCE IT CROSSES THE ROCKIES THE MOUNTAINS. IT
IS EXPECTED TO START DEEPENING RAPIDLY LATE TONIGHT IN THE LEE OF
THE CENTRAL ROCKIES AND THEN CONTINUE TO STRENGTHEN AS IT MOVES
EAST/NORTHEAST TOWARD THE GREAT LAKES. THE MODELS HAVE ALSO BEEN
CONSISTENT IN SHOWING THIS WAVE COMING THROUGH AS AN OPEN WAVE
WITH A POSITIVE TILT. AS THIS IS OCCURRING...THE ENERGY OVER THE
PACIFIC COMES ON SHORE AND TAKES A TRACK ACROSS SOUTHERN CANADA
BEFORE FORMING A CLOSED LOW OVER THE HIGH PLAINS TUESDAY
AFTERNOON. THE FIRST SHORT WAVE TROUGH IS EXPECTED TO MOVE RAPIDLY
OVER THE AREA TUESDAY NIGHT WITH THE CLOSED LOW OPENING UP INTO AN
OPEN WAVE AND THEN TRACKING TOWARD THE NORTHERN GREAT LAKES. WITH
THIS SCENARIO...THE SOUTHERN WAVE IS EXPECTED TO BE THE DOMINANT
WEATHER MAKER FOR THE LOCAL REGION.

THIS SHORT WAVE TROUGH SHOULD PRODUCE STRONG PV ADVECTION IN THE
500-300 MB LAYER TUESDAY NIGHT WITH THIS FORCING BEING AIDED BY
THE REGION COMING UNDER THE LEFT EXIT REGION OF THE UPPER LEVEL
JET. MODERATE AND DEEP QG CONVERGENCE SHOULD OCCUR AHEAD OF THE
WAVE COMING ACROSS THE AREA TUESDAY AFTERNOON INTO THE EARLY
EVENING. IN THE LOWER LEVELS...SOME DIFFERENCES BETWEEN THE MODELS
ON THE TRACK OF THE SURFACE LOW. THE 23.12Z NAM IS THE FARTHEST
NORTH BRINGING THE SURFACE LOW FROM SOUTHERN IOWA INTO SOUTHERN
WISCONSIN. WITH THIS TRACK...IT WRAPS THE MOST WARM AIR ALOFT OVER
THE AREA TO CREATE THE POTENTIAL FOR MORE FREEZING RAIN. THE
23.12Z GFS AND ECMWF ARE FARTHER SOUTH WITH THE SURFACE LOW TAKING
IT FROM MISSOURI TOWARD LOWER LAKE MICHIGAN WHICH BRINGS MUCH
LESS WARM INTO THE AREA AND WOULD GIVE THE POTENTIAL FOR MORE
SNOW. WHILE NOT TOTALLY IGNORING THE NAM SOLUTION...HAVE FAVORED
MORE OF A SOUTHERN TRACK...BUT EVEN WITH THIS...THERE WILL STILL
BE PRECIPITATION TYPE CONCERNS. THE WARM AIR ALOFT SHOULD START TO
MOVE IN TUESDAY AFTERNOON AND REMAIN OVER THE AREA INTO WEDNESDAY
MORNING. THERE COULD ALSO BE A LOSS OF ICE IN THE CLOUD LAYER AS
THE SHORT WAVE TROUGH MOVES PAST. WORKING THESE POSSIBILITIES IN
THE FORECAST YIELDS A WINTRY MIX OF RAIN...SNOW...SLEET AND
FREEZING RAIN BEFORE TRANSITIONING OVER TO ALL RAIN BY WEDNESDAY
AFTERNOON FOR THOSE AREAS STILL UNDER THE INFLUENCE OF THE PASSING
NORTHERN SYSTEM AND RECEIVING SOME LIGHT PRECIPITATION.

WILL START TO BRING THE PRECIPITATION INTO THE SOUTHWEST SECTIONS
WITH 20 TO 80 PERCENT CHANCES WEST OF THE MISSISSIPPI RIVER FOR
THE LATE AFTERNOON WITH THIS BEING ALMOST ALL RAIN. WITH THE BEST
FORCING OCCURRING TUESDAY NIGHT...THE ENTIRE AREA WILL HAVE A 100
PERCENT CHANCE AT SOME POINT. HOWEVER...THIS IS WHERE THE MIXED
PRECIPITATION WILL BE WITH THE RAIN GOING OVER TO SNOW...POSSIBLY
MIXED WITH SLEET IN THE EVENING. THE FREEZING RAIN THEN WORKS INTO
THE MIX OVERNIGHT TUESDAY WITH THE POTENTIAL LOSS OF ICE. THIS ALL
LEADS TO SNOW ACCUMULATIONS OF 1 TO 3 INCHES MAINLY ALONG AND
NORTH OF INTERSTATE 90 WITH A FEW HUNDREDTHS OF ICE ACCUMULATIONS
FOR THE SAME AREAS. GENERAL FEELING IS THAT THIS EVENT WILL NEED A
WINTER WEATHER ADVISORY ON IT UNLESS THE MORE SOUTHERN AND COLDER
SOLUTIONS VERIFY WHICH COULD BRING MORE SNOW FROM SOUTHEAST
MINNESOTA INTO NORTH CENTRAL WISCONSIN.

.LONG TERM...(THURSDAY THROUGH MONDAY)
ISSUED AT 311 PM CDT MON MAR 23 2015

SOME LIGHT PRECIPITATION COULD LINGER INTO THURSDAY ACROSS
WISCONSIN UNTIL THE NORTHERN SYSTEM MOVES PAST THE REGION. THE
NEXT CHANCE FOR SOME PRECIPITATION WILL COME SATURDAY NIGHT INTO
SUNDAY. THE UPPER LEVEL RIDGE IS EXPECTED TO BUILD OVER THE
WESTERN CONUS THROUGH THE END OF THE WEEK PLACING THE GREAT LAKES
REGION INTO NORTHWEST FLOW AGAIN. THE MODELS CONTINUE TO BE IN
GOOD AGREEMENT IN SHOWING A PACIFIC SYSTEM TOPPING THIS RIDGE AND
DROPPING ACROSS THE NORTHERN GREAT LAKES AND SOUTHERN CANADA TO
CLOSE OUT THE WEEKEND. THE FOCUS OF PRECIPITATION FOR THE REGION
WILL BE ALONG THE COLD FRONT WILL COME ACROSS AS THE SHORT WAVE
TROUGH PASSES TO THE NORTHEAST. WILL HAVE SOME 20 TO 30 PERCENT
CHANCES FOR RAIN AND SNOW WITH THE PASSAGE OF THIS SYSTEM.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1135 PM CDT MON MAR 23 2015

AN MVFR STRATUS DECK WILL BE CLEAR OF RST BY 7Z AS DRIER LOW LEVEL
AIR CONTINUES TO PUSH INTO THE REGION. THE MAIN FOCUS WILL THEN
SHIFT TO TUESDAY EVENING AS PRECIPITATION MOVES IN FROM THE
SOUTHWEST. A SLIGHT WARM LAYER ABOVE FREEZING COULD CAUSE THE
PRECIPITATION TO START OUT AS SLEET/SNOW PELLETS...MORE SO AT LSE
THAN RST...BEFORE CHANGING OVER TO ALL SNOW. VISIBILITY WILL
LIKELY DROP TO IFR AS THE SNOW MOVES IN WITH THE HEAVIEST PERIOD
COMING IN THE EVENING.

&&

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

$$

SHORT TERM...04
LONG TERM...04
AVIATION...HALBACH


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