Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 140440
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1140 PM CDT SUN APR 13 2014

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 343 PM CDT SUN APR 13 2014

BUSY PERIOD TONIGHT INTO TOMORROW MORNING AS A LOW PRESSURE SYSTEM
TRACKS THROUGH NORTHERN ILLINOIS. HEAVY RAIN...SNOW...AND STRONG
WINDS ARE ALL CONCERNS TONIGHT INTO TOMORROW MORNING.

CURRENTLY...THE LEAD MID LEVEL TROUGH IS PROPAGATING TO THE NORTH
ACROSS THE MID-MISSISSIPPI RIVER VALLEY WITH SOME LOW LEVEL
CONVERGENCE OCCURRING ALONG A SOUTHWEST TO NORTHEAST ORIENTED WARM
FRONT THAT RUNS FROM SOUTHEAST IOWA THROUGH SOUTHERN WISCONSIN.
MODERATE TO HEAVY RAIN HAS ALREADY MOVED INTO NORTHEAST IOWA AND
SOUTHWEST WISCONSIN AND WILL CONTINUE TO TRACK TO THE NORTHEAST
INTO THIS EVENING AS THE SURFACE LOW MOVES UP IN THE REGION. MOST
OF THE 0-3KM MUCAPE THAT THE 13.19Z RAP SHOWS STAYS IN NORTHERN
ILLINOIS AND DOES NOT REACH THE REGION. SO...THINKING THAT THERE
SHOULD NOT BE MUCH LIGHTNING WITH THIS RAIN INTO THE EVENING
HOURS. WITH 1 TO 2 INCHES OF RAIN STILL FORECAST FOR THE SAME
AREAS THAT WERE HIT BY 1 TO 3 INCHES OF RAIN YESTERDAY...HAVE KEPT
THE FLOOD WATCH GOING FOR NORTHEAST IOWA AND SOUTHWEST WISCONSIN.

TO THE WEST SIDE OF THE SYSTEM WE GO WHERE THE CONCERN IS ON WHEN
THE THERMAL PROFILE WILL COOL ENOUGH TO CHANGE THE PRECIPITATION
OVER TO ALL SNOW ALONG WITH HOW WINDY IT WILL BE. IN REGARD TO THE
SNOW...WITH LOW TO MID LEVEL COLD AIR ADVECTION KICKING IN THIS
EVENING AS THE LOW DEEPENS...THE PRECIPITATION TYPE WILL BE
DEPENDENT UPON WHAT THE SURFACE TEMPERATURES ARE. LOOKING OUT WEST
RIGHT NOW...MOST OBSERVATIONS THAT ARE REPORTING SNOW ARE IN THE
30F TO 35F RANGE THOUGH SOME OF THESE TEMPERATURE DROPS APPEAR TO
BE DUE TO EVAPORATIVE COOLING THANKS TO THE PRECIPITATION FALLING
THROUGH THE COLUMN. BASED ON THE 13.19Z RAP & 13.12Z NAM/GFS
SOUNDINGS...IT LOOKS LIKE THE CHANGE OVER SHOULD OCCUR TO ALL SNOW
THIS EVENING BETWEEN 8-10PM IN NORTH CENTRAL IOWA AND SOUTHEAST
MINNESOTA. THIS CHANGE OVER WILL THEN GRADUALLY PUSH EASTWARD INTO
WESTERN WISCONSIN OVERNIGHT. SNOW TOTALS ARE PROBLEMATIC AS A
RESULT SINCE A LOT HINGES ON HOW FAST THE CHANGE OVER OCCURS...IS
THERE STRONG FORCING STILL THERE AS THE COLD AIR ARRIVES...AND
ALSO IF THERE EVEN IS ICE THERE AS A LOT OF THE SOUNDINGS SHOW A
DRY LAYER BETWEEN -8C TO -20C. MOST OF THE 13.12Z COBB DATA FROM
THE NAM/GFS IS SHOWING ABOUT 1 TO 2 INCHES OCCURRING OVERNIGHT
THOUGH A LOT OF THE SREF DATA IS MUCH HIGHER THAN THAT. GIVEN THE
NUMBER OF NEGATIVES WORKING AGAINST THIS...TRENDED TOWARD THESE
LOWER TOTALS WHICH STILL ARE A BIT HIGHER THAN WHAT PREVIOUSLY WAS
BEING FORECAST BY GUIDANCE. THE MAIN SNOW SHOULD FALL BETWEEN
7PM-1AM IN NORTHEAST IOWA/SOUTHEAST MINNESOTA AND THEN BETWEEN
1AM-7AM IN WESTERN WISCONSIN/FAR NORTHEAST IOWA.

WINDS WILL CONTINUALLY INCREASE THROUGH TONIGHT AS THE PRESSURE
GRADIENT TIGHTENS UP WITH THE LOW. THE STRONGEST LOW LEVEL WINDS
HAVE ALREADY DEVELOPED ACROSS WESTERN IOWA WHERE 30 TO 40KT WINDS
ARE FAIRLY WIDESPREAD IN THE AREA WHERE SNOW IS FALLING. CONCERNED
THAT THESE CONDITIONS WILL TRANSLATE EASTWARD INTO NORTHEAST IOWA
AND SOUTHEAST MINNESOTA THIS EVENING. THE STRONGEST WINDS LOOK
LIKE THEY WILL MAINLY BE IN NORTHEAST IOWA WITH BUFKIT SOUNDINGS
SHOWING SOME 35 TO 40KT WINDS MIXING DOWN AS THE SNOW IS COMING
DOWN. DISCUSSED THE IDEA OF DOING A WINTER WEATHER OR WIND ADVISORY
WITH MPX/DMX...BUT DECIDED THAT THE WIND GUSTS MAY NOT HIT
ADVISORY CRITERIA AND SNOW AMOUNTS MAY NOT BE HIGH ENOUGH TO CAUSE
A LARGE IMPACT. CONDITIONS WILL HAVE TO BE MONITORED CLOSELY THIS
EVENING FOR A POSSIBLE QUICK UPGRADE WITH THE 9PM TO 3AM TIME
FRAME THE MAIN PERIOD OF CONCERN.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 343 PM CDT SUN APR 13 2014

THE MAIN STORIES THROUGH THIS WEEK ARE WITH THE POTENTIAL
ACCUMULATING SNOW ON TUESDAY NIGHT/WEDNESDAY AND ANOTHER SYSTEM
LATER IN THE WEEK.

MORE FOCUS WENT INTO THE TUESDAY NIGHT/WEDNESDAY SYSTEM SINCE
THERE IS QUITE A BIT OF UNCERTAINTY WITH THE LATE WEEK SYSTEM. THE
13.12Z NAM/GFS DEVELOPS A BAND OF SNOW ACROSS NORTHERN WISCONSIN
LATE TUESDAY NIGHT WHILE THE 13.12Z ECMWF KEEPS US DRY. SOME
ACCUMULATING SNOW IS LIKELY IN THE NAM/GFS SCENARIOS THOUGH ENOUGH
UNCERTAINTY IS THERE THANKS TO THE ECMWF. IT LOOKS LIKE WE GET
WARM SECTORED ON WEDNESDAY AS THE SYSTEM STALLS OUT WITH THE
PRECIPITATION SETTING UP FROM UPPER MICHIGAN DOWN THROUGH CENTRAL
IOWA ON THURSDAY. THE 13.12Z GFS THEN SPINS UP A POTENT SYSTEM FOR
FRIDAY THAT TRACKS THROUGH WISCONSIN WHILE EH ECMWF HARDLY HAS A
LOW DEVELOPING.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 1140 PM CDT SUN APR 13 2014

AS SHORT WAVE CONTINUES TO PUSH EAST TONIGHT...PRECIPITATION HAS
BEEN WAINING. COLUMN HAS BEEN COOLING AS WELL ALLOWING RAIN TO
CHANGE OVER TO SNOW FROM WEST TO EAST. BUT OVERALL CONDITIONS HAVE
BEEN IMPROVING WITH LESS LIFR AND MORE MVFR BEING OBSERVED AROUND
THE AREA.

OVER THE NEXT FEW HOURS...EXPECT RAIN AND SNOW TO END. BEFORE THEN
COULD SEE A DEFORMATION ZONE DEVELOP AND BRING ONE MORE ROUND OF
SNOW TO KRST BEFORE ENDING. MVFR CEILINGS EXPECTED TOWARDS DAYBREAK
AND THEN AS SYSTEM EXITS...COULD SEE VFR FOR MUCH OF THE DAY.

A BIT UNSURE ON WHAT CLOUDS WILL DO MONDAY AFTERNOON AS UPPER TROUGH
SETTLES IN. COULD SEE SOME LOW CLOUD DEVELOPMENT GIVEN MID APRIL SUN
BUT AM BANKING THAT MID LEVEL CLOUDS AROUND WILL BE ABOUT IT. STIFF
NORTHWEST WINDS SHOULD ALSO SUBSIDE AS WEATHER SYSTEM EXITS BY
MONDAY EVENING.

&&

.HYDROLOGY...
ISSUED AT 343 PM CDT SUN APR 13 2014

WITH MODERATE TO AT TIMES HEAVY RAIN FALLING INTO TONIGHT...WILL
KEEP THE FLOOD WATCH GOING FOR NORTHEAST IOWA AND SOUTHWEST
WISCONSIN. WITH 1 TO 3 INCHES OF RAIN FALLING LAST NIGHT ACROSS
THIS AREA AND ANOTHER 1 TO 2 INCHES POSSIBLE...SAW NO NEED TO DROP
IT. THERE DOES NOT APPEAR TO BE MUCH INSTABILITY THAT MAKES IT UP
IN THE REGION THIS AFTERNOON INTO TONIGHT...SO MOST OF THE RAIN
SHOULD NOT FALL AT A GREAT ENOUGH OF A RATE TO PROMPT FLASH
FLOODING.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FLOOD WATCH UNTIL 1 AM CDT MONDAY FOR WIZ043-044-053>055-061.

MN...NONE.

IA...FLOOD WATCH UNTIL 1 AM CDT MONDAY FOR IAZ030.

&&

$$

SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION...SHEA
HYDROLOGY...HALBACH



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