Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 212032
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
332 PM CDT MON JUL 21 2014

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 331 PM CDT MON JUL 21 2014

MAIN FORECAST CONCERNS ARE SEVERE THUNDERSTORM POTENTIAL LATE
TONIGHT OVER NORTH CENTRAL WISCONSIN AND HEAT INDEX VALUES LATE
TUESDAY MORNING INTO TUESDAY AFTERNOON OVER PORTIONS OF NORTHEAST
IOWA INTO FAR SOUTHWEST WISCONSIN.

LATEST RADAR IMAGERY SHOWS THUNDERSTORMS DEVELOPING OVER PORTIONS OF
CENTRAL NORTH DAKOTA. THESE SHOULD BE THE BIRTH OF A THUNDERSTORM
COMPLEX THAT WILL RACE EAST TONIGHT ACROSS NORTHERN MINNESOTA INTO
PORTIONS OF NORTHERN WISCONSIN AND UPPER MICHIGAN. MOST OF THE
MESOSCALE MODEL GUIDANCE KEEPS THIS COMPLEX NORTH OF THE INTERSTATE
94 CORRIDOR. HOWEVER...THE NAM...WHICH IS A MAJOR OUTLIER AT THIS
TIME...SHOWS CONVECTION FIRING OVER WEST CENTRAL MINNESOTA LATE
THIS AFTERNOON INTO THIS EVENING THEN THIS CONVECTION RACES
SOUTHEAST INTO THE FORECAST AREA. LOOKING AT FORECAST SOUNDINGS
OVER MUCH OF THE FORECAST AREA THERE IS AN IMPRESSIVE ELEVATED
MIXED LAYER WHICH IS RESULTING IN A STRONG CAP IN PLACE. THE
CONVECTION WILL HAVE TO OVERCOME THIS CAP AND WITHOUT A STRONG LOW
LEVEL JET THIS WILL BE DIFFICULT TO DO. THE 17Z HRRR SHOWS A FEW
CELLS MAKING IN INTO WEST CENTRAL WISCONSIN AFTER MIDNIGHT SO WILL
HAVE TO SEE IF THIS PANS OUT. HAVE DECIDED TO REDUCE POPS ACROSS
MUCH OF THE FORECAST AREA TONIGHT WITH THE EXCEPTION OF CLARK AND
TAYLOR COUNTY WHERE THE MCS COULD IMPACT THESE AREAS WITH DAMAGING
WINDS THE MAY CONCERN.

A COLD FRONT THEN SAGS SOUTH ACROSS THE AREA ON TUESDAY. SOME OF
THE WARMEST AIR AT 925 MB MAKES IT INTO NORTHEAST IOWA INTO FAR
SOUTHWEST WISCONSIN WHERE 925 MB TEMPERATURES CLIMB TO AROUND 27
C. TEMPERATURES COULD CLIMB TO THE UPPER 80S TO AROUND 90 OVER
PORTIONS OF NORTHEAST IOWA AND FAR SOUTHWEST WISCONSIN. THESE
TEMPERATURES COMBINED WITH DEWPOINTS IN THE MID TO UPPER 70S WILL
PRODUCE HEAT INDEX VALUES AROUND 100. THIS HEAT LOOKS TO BE VERY
SHORT LIVED WITH THE COLD FRONT SWEEPING THROUGH LATE TOMORROW
AFTERNOON SO HAVE HAVE NOT ISSUED A HEAT ADVISORY AT THIS TIME.
SHOWERS AND STORMS WILL BE POSSIBLE ALONG THE FRONT TUESDAY
AFTERNOON INTO EARLY TUESDAY EVENING BUT AGAIN THE CAP WILL BE A
MAJOR LIMITING FACTOR. MOST OF THE FORECAST MODELS KEEP THE AREA
DRY. GIVEN THE AMOUNT OF SURFACE BASED CAPE THAT DEVELOPS AHEAD
OF THE FRONT OVER NORTHEAST IOWA AND FAR SOUTHWEST
WISCONSIN...COULD SEE A STORM OR TWO DEVELOP ALONG THE FRONT LATE
IN THE AFTERNOON SO WILL KEEP CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGH THE LATE AFTERNOON INTO THE EARLY EVENING.
VERY COMFORTABLE TEMPERATURES RETURN IN THE WAKE OF THE FRONT
TUESDAY NIGHT WITH TEMPERATURES FALLING INTO THE UPPER 50S TO
LOWER 60S.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 331 PM CDT MON JUL 21 2014

HIGH PRESSURE BUILDS INTO THE REGION TUESDAY NIGHT AND REMAINS OVER
THE REGION THROUGH THURSDAY PROVIDING QUIET AND COMFORTABLE CONDITIONS.
PLAN ON HIGHS IN THE 70S WITH LOWS IN THE 50S TO AROUND 60. WITH
THE HIGH OVERHEAD WILL HAVE TO KEEP AN EYE ON THE POTENTIAL FOR
SOME PATCHY VALLEY FOG DURING THE LATE NIGHT AND EARLY MORNING
HOURS THURSDAY MORNING...BUT CLOUD COVER COULD PREVENT THIS FROM
FORMING. CHANCES FOR SHOWERS AND THUNDERSTORMS RETURN THURSDAY
NIGHT INTO THE WEEKEND AS ACTIVE NORTHWEST FLOW SETS UP ACROSS THE
REGION. A TROUGH DIVES INTO THE UPPER MISSISSIPPI RIVER VALLEY ON
SUNDAY AND DEEPENS A LARGER SCALE TROUGH OVER THE ENTIRE GREAT
LAKES REGION EARLY NEXT WEEK. THIS WOULD SET THE STAGE FOR WELL
BELOW NORMAL TEMPERATURES OVER THE AREA GOING INTO EARLY NEXT
WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1225 PM CDT MON JUL 21 2014

GOOD VFR CONDITIONS WILL PREVAIL THIS AFTERNOON AND EVENING AS
DIURNAL WARMING INCREASES THE MIXING DEPTH...WITH ANY CUMULUS IN THE
4K-5K FT RANGE. INCREASED MIXING SHOULD KEEP THE BOUNDARY LAYER HAZE
TO A MINIMUM AS WELL. THE DEEPER MIXING AND MDT PRESSURE GRADIENT
ACROSS THE AREA WILL RESULT IN SOME WIND GUSTS IN THE 20KT RANGE AT
BOTH KRST/KLSE THIS AFTERNOON.

A STORM COMPLEX IS STILL EXPECTED TO DEVELOP OVER EASTERN ND/
NORTHERN MN THIS EVENING. BULK OF THE FORCING TAKES THIS COMPLEX
EAST-SOUTHEAST ACROSS MN/NORTHERN WI OVERNIGHT/EARLY TUE MORNING. A
COUPLE OF MODEL SOLUTIONS BRING THIS COMPLEX SOUTHEAST DOWN THE MS
RIVER OVERNIGHT...AND INTO THE KLSE/KRST AREAS IN THE 09Z-12Z TIME
FRAME. THIS LOOKS RATHER UNLIKELY WITH VERY WARM TEMPERATURES AROUND
700MB CAPPING THE AIRMASS OVER SOUTHEAST MN/SOUTHWEST WI TONIGHT AND
THE MAIN FORCING OVER NORTHERN WISCONSIN. LEFT THE KRST TAF DRY LATE
TONIGHT AND ONLY CARRIED A 10-13Z VCSH MENTION AT KLSE. GRADIENT
WINDS OF 10-15KTS TONIGHT SHOULD KEEP LATE NIGHT BR TO A MINIMUM. A
COLD FRONT DROPS ACROSS THE AREA TUE...AROUND 15Z AT KRST AND 18Z AT
KLSE. FRONT WILL BRING A SWITCH TO NORTHWEST WINDS AND A DRIER LOW
LEVEL AIRMASS TO THE TAF SITES LATER TUE MORNING/TUE AFTERNOON.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...HEAT ADVISORY UNTIL 9 PM CDT THIS EVENING FOR MNZ079-086-087-094-
     095.

IA...HEAT ADVISORY UNTIL 9 PM CDT THIS EVENING FOR IAZ008-009-018-019.

&&

$$

SHORT TERM...WETENKAMP
LONG TERM...WETENKAMP
AVIATION.....RRS


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