Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 291232
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
732 AM CDT SUN MAR 29 2015

.UPDATE...
ISSUED AT 719 AM CDT SUN MAR 29 2015

LIGHT FREEZING RAIN HAS PRODUCED A GLAZE OF ICE ON UNTREATED
SURFACES AND ELEVATED OBJECTS ACROSS PORTIONS OF SOUTHEAST
MINNESOTA...NORTHEAST IOWA...AND PORTIONS OF EXTREME WESTERN
WISCONSIN. THIS ACTIVITY WILL CONTINUE TO PUSH EAST INTO CENTRAL
WISCONSIN THROUGH 8 TO 9 AM. HAVE ISSUED A FREEZING RAIN ADVISORY
FOR ALL OF SOUTHWEST INTO CENTRAL WISCONSIN THROUGH 9 AM WHERE
LIGHT ICING IS EXPECTED ON UNTREATED ROADS.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 344 AM CDT SUN MAR 29 2015

WATER VAPOR SATELLITE THIS MORNING SHOWS A POTENT SHORT WAVE
TROUGH OVER THE DAKOTAS. REGIONAL RADARS SHOWING A BROKEN BAND OF
LIGHT RAIN AHEAD OF THE SHORT WAVE TROUGH FROM NORTHWEST MINNESOTA
INTO WESTERN IOWA. THE SHORT WAVE TROUGH WILL CONTINUE TO MOVE
SOUTHEAST AND TRACK ACROSS THE REGION THIS MORNING BRINGING A
ROUND OF STRONG PV ADVECTION WITH IT IN THE 500-300 MB LAYER.
MODERATE QG CONVERGENCE OVER A DEEP LAYER...FROM 1000-300
MB...WILL OCCUR WITH THE PASSAGE OF THE WAVE AS WELL. IN THE LOW
LEVELS...THE MAIN SURFACE LOW WILL BE WELL NORTH OF THE AREA
ACROSS SOUTHERN CANADA...BUT THE WAVE WILL PUSH A COLD FRONT
THROUGH THE REGION. THE BAROCLINIC ZONE WITH THE COLD FRONT IS NOT
VERY STRONG WHICH RESULTS IN ONLY SOME WEAK FRONTOGENESIS
OCCURRING IN THE 1000-850 MB LAYER. THE WARM AIR ADVECTION AHEAD
OF THE COLD FRONT WILL PRODUCE 3 TO 4 UBAR/S OF UP GLIDE ON THE
290K ISENTROPIC SURFACE. THE 29.00Z KMPX SOUNDING SHOWED A PRETTY
DRY AIR MASS WAS IN PLACE...BUT BASED ON THE RADAR RETURNS AND THE
SURFACE OBSERVATIONS...IT APPEARS THAT THE STRONG FORCING WITH THE
SHORT WAVE TROUGH IS OVERCOMING THIS DRY AIR AND ALLOWING
SATURATION TO OCCUR. PLAN TO CONTINUE WITH THE CATEGORICAL
PRECIPITATION CHANCES THIS MORNING ALONG AND AHEAD OF THE COLD
FRONT. THE TYPE OF PRECIPITATION REMAINS A CONCERN. THE WARM AIR
ADVECTION WILL CONTINUE TO PRODUCE A WARM LAYER ALOFT THAT WILL BE
ENOUGH FOR PARTIAL TO COMPLETE MELTING IF AND WHEN ICE IS PRESENT
IN THE CLOUDS. BECAUSE OF THIS...STILL EXPECTING THE POSSIBILITY
OF SOME MESSY WEATHER THIS MORNING. THE PARTIAL MELTING COULD
ALLOW SOME SLEET TO MIX IN WITH THE RAIN OVER PORTIONS OF
SOUTHEAST MINNESOTA INTO NORTH CENTRAL WISCONSIN. OVER CENTRAL
INTO SOUTHWEST WISCONSIN...SOME FREEZING RAIN COULD OCCUR FOR A
COUPLE OF HOURS BEFORE TEMPERATURES RISE ABOVE FREEZING. ACROSS
WESTERN MINNESOTA...SURFACE TEMPERATURES HAVE BEEN RISING WITH THE
ARRIVAL OF THE PRECIPITATION WITH JUST RAIN REPORTED SO FAR. IF
THIS TREND CONTINUES...THIS COULD MITIGATE THE FREEZING RAIN
THREAT ADDING SOME ADDITIONAL UNCERTAINTY TO WHAT TYPE OF
PRECIPITATION WILL OCCUR. WITH THIS UNCERTAINTY AND THE SHORT
DURATION OF ANY MIXED PRECIPITATION...DO NOT PLAN TO ISSUE A
WINTER WEATHER ADVISORY.

ONCE THE COLD FRONT MOVES THROUGH...WINDY CONDITIONS ARE EXPECTED
TO DEVELOP THIS AFTERNOON. A TROPOPAUSE FOLD BEHIND THE SHORT WAVE
TROUGH IS EXPECTED TO GET DOWN TO ABOUT 500 MB OR SO. THIS WILL BE
ACCOMPANIED BY GOOD...DEEP SUBSIDENCE WITH LOW LEVEL LAPSE RATES
OF 7 TO 9 C/KM UP THROUGH ABOUT 850 TO 800 MB. WITH A TIGHT
GRADIENT BEHIND THE FRONT AND STRONG SURFACE PRESSURE
RISES...EXPECTING THE SUSTAINED WEST TO NORTHWEST WINDS TO BE IN
THE 20 TO 30 MPH FOR MUCH OF THE AREA. WIND GUSTS AROUND 35 MPH
ARE EXPECTED ALONG AND EAST OF THE MISSISSIPPI RIVER...BUT OVER
THE TYPICALLY WINDY AREAS OF SOUTHEAST MINNESOTA AND NORTHEAST
IOWA...THESE SHOULD APPROACH 45 MPH AT TIMES. WILL ISSUE A WIND
ADVISORY TO COVER THE HIGHER SUSTAINED WINDS AND GUSTS EXPECTED
OVER THE WESTERN SECTIONS OF THE AREA.

NORTHWEST FLOW ALOFT WILL DEVELOP OVER THE UPPER MIDWEST ONCE THE
SHORT WAVE TROUGH GOES THROUGH TODAY. THE NEXT SHORT WAVE TROUGH
IS EXPECTED TO TOP THE WESTERN RIDGE AND SLIDE ACROSS THE REGION
MONDAY AFTERNOON AND NIGHT. THE 29.00Z MODELS STILL AT ODDS WITH
THE TRACK OF THIS SHORT WAVE TROUGH AND ASSOCIATED SURFACE LOW.
THE ECMWF CONTINUES TO BE THE FARTHEST SOUTHWEST AND CONTINUES TO
SHOW SOME LIGHT PRECIPITATION ACROSS WISCONSIN WHILE THE GFS IS
FARTHER NORTHEAST AND JUST BRUSHES THE NORTHERN AND EASTERN
SECTIONS WITH SOME PRECIPITATION WITH THE NAM THE FARTHEST
NORTHEAST KEEPING THE AREA DRY. WITH THE GFS BEING SOME WHAT OF A
COMPROMISE SOLUTION AT THIS POINT...WILL TREND TOWARD IT WITH SOME
SMALL CHANCES IN THE I94 CORRIDOR MONDAY AFTERNOON AND EVENING.

.LONG TERM...(TUESDAY NIGHT THROUGH SATURDAY)
ISSUED AT 344 AM CDT SUN MAR 29 2015

THE ACTIVE PATTERN WILL CONTINUE INTO THE MIDDLE PART OF THE WEEK.
A STRONG SHORT WAVE TROUGH IS EXPECTED TO COME IN OFF THE PACIFIC
AND PUSH THE MEAN RIDGE AXIS INTO THE EASTERN PART OF THE COUNTRY.
RIGHT NOW...ALL THE MODELS ARE IN GOOD AGREEMENT IN TAKING THE
BEST PART OF THIS SHORT WAVE TROUGH ACROSS THE HIGH PLAINS INTO
SOUTHERN CANADA...BUT IT LOOKS LIKE THERE WILL BE SOME WEAKER
WAVES UNDERCUTTING THE MAIN SHORT WAVE TROUGH AND COMING ACROSS
THE REGION. THE MAIN SURFACE LOW WITH THIS SYSTEM WILL BE WELL TO
THE NORTH BUT THE TRAILING COLD FRONT SHOULD COME ACROSS THE AREA
WEDNESDAY NIGHT. THE GFS SHOWS DEW POINTS GETTING INTO THE 50S
WEDNESDAY AFTERNOON AHEAD OF THE COLD FRONT AND PRODUCES MU CAPES
OF 500-1000 J/KG FOR MUCH OF THE WESTERN PART OF THE FORECAST
AREA. THESE DEW POINTS ARE LIKELY TOO HIGH WITH VALUES IN THE
UPPER 40S MORE LIKELY...BUT THIS WOULD STILL BE ENOUGH TO GENERATE
DECENT CAPE AND HAVE ADDED IN ISOLATED THUNDER ACROSS THE WEST
WEDNESDAY AFTERNOON AND THEN ACROSS THE SOUTHERN SECTIONS FOR
WEDNESDAY EVENING. WILL HAVE 20 TO 50 PERCENT RAIN CHANCES ALONG
WITH THE THUNDER WEDNESDAY AFTERNOON AND THEN 50 TO 60 PERCENT
CHANCES WEDNESDAY NIGHT. THE SOUTHERN PART OF THE COLD FRONT COULD
STALL OUT NOT TOO FAR SOUTH OF THE AREA WHICH COULD KEEP SOME
SMALL PRECIPITATION CHANCES ACROSS THE SOUTHERN SECTIONS OF THE
AREA THURSDAY INTO FRIDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 732 AM CDT SUN MAR 29 2015

LIGHT FREEZING RAIN/RAIN WILL END AT THE TAF SITES BY 14Z AS
WARMER AIR PUSHES INTO THE REGION. EXPECT WINDY CONDITIONS TODAY
WITH SOUTH WINDS THIS MORNING AT 19 TO 25 KTS...GUSTING TO 33 KTS
AT TIMES. WINDS WILL SWITCH TO THE NORTHWEST LATE THIS MORNING
INTO THIS AFTERNOON AN INCREASE TO 20 TO 28 KTS WITH GUST
APPROACHING 39 KTS AT TIMES AT KRST. A ROUND OF LIGHT RAIN SHOWERS
ARE POSSIBLE THIS AFTERNOON. PERIODS OF MVFR CEILINGS ARE EXPECTED
TODAY ESPECIALLY LATE THIS MORNING INTO THIS AFTERNOON AS THE COLD
FRONT MOVES IN. LOOK FOR WINDS TO FINALLY SUBSIDE THIS EVENING AS
HIGH PRESSURE MOVES IN.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...FREEZING RAIN ADVISORY UNTIL 9 AM CDT THIS MORNING FOR WIZ017-
     029-032>034-041>044-053>055-061.

MN...WIND ADVISORY FROM 11 AM THIS MORNING TO 6 PM CDT THIS EVENING
     FOR MNZ079-086-087-094-095.

IA...WIND ADVISORY FROM 11 AM THIS MORNING TO 6 PM CDT THIS EVENING
     FOR IAZ008>010-018-019-029.

&&

$$

UPDATE...WETENKAMP
SHORT TERM...04
LONG TERM...04
AVIATION...WETENKAMP



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