Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 240415
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1115 PM CDT THU JUL 23 2015

.SHORT TERM...(TONIGHT THROUGH FRIDAY NIGHT)
ISSUED AT 219 PM CDT THU JUL 23 2015

MAIN FOCUS IS ON LIKELIHOOD OF SHOWERS/STORM MOVING INTO THE AREA
EARLY FRIDAY MORNING...AND THEN SEVERE THUNDERSTORM POTENTIAL LATE
FRIDAY AFTERNOON INTO FRIDAY EVENING WITH COLD FRONTAL PASSAGE.

SURFACE MAP THIS AFTERNOON HAD HIGH PRESSURE CENTERED OVER SOUTHERN
LAKE MICHIGAN WITH RIDGING INTO WI. VISIBLE SATELLITE SHOWING FAIRLY
EXTENSIVE FIELD OF CUMULUS ACROSS THE REGION WITH MOIST SOUTHERLY
FLOW ADVECTING IN ON RETURN FLOW ON THE BACKSIDE OF THE HIGH.
OTHERWISE...TEMPERATURES THIS AFTERNOON WERE IN THE 80-85 DEGREE
RANGE.

FOR TONIGHT INTO FRIDAY MORNING...MID-LEVEL SHORTWAVE
TROUGH/THUNDERSTORMS OVER THE DAKOTAS THIS AFTERNOON EXPECTED TO
UPSCALE AND ADVANCE SOUTHEAST TOWARD THE REGION BY EARLY FRIDAY
MORNING AS 850MB MOISTURE TRANSPORT CONTINUES TO FUEL THE
CONVECTION. APPEARS THIS COMPLEX OF STORMS COULD BECOME SEVERE WITH
DAMAGING WINDS/LARGE HAIL AS IT MOVES INTO MN...THEN BE ON A
WEAKENING TREND AS THEY HEAD INTO OUR AREA AFTER 12Z. THIS IS DUE TO
THE STORMS MOVING AWAY FROM THE BETTER CAPE AXIS/SOURCE WHICH WILL
BE IN PLACE ACROSS SOUTH CENTRAL MN/WESTERN IA. HAVE BUMPED POPS
INTO LIKELY CATEGORY FROM SOUTHEAST MN INTO NORTH CENTRAL WI IN THE
12-16Z TIME FRAME...TAPERING OFF TO CHANCY POPS AFTERWARDS AS THE
COMPLEX FALLS APART/MOVES EAST OF THE AREA.

WILL THEN BE FOCUSING ATTENTION TO INCOMING COLD FRONT BY LATER
FRIDAY AFTERNOON/FRIDAY NIGHT. PLENTY OF CAPE AND WIND SHEAR FOR A
SEVERE RISK. HOWEVER...SEVERE THREAT WILL BE CONDITIONAL DUE TO A
FAIRLY STRONG CAP THAT WILL BE IN PLACE DUE TO SOME SUBSIDENCE
BEHIND PASSING SHORTWAVE TROUGH. NAM/ARW MESOWRF MODEL REFLECTIVITY
DOES SHOW SCATTERED CONVECTION FIRING MAINLY AFTER 23Z WITH
WEAKENING CAP...BUT OTHER MODELS LESS ENTHUSED. DAMAGING WINDS AND
LARGE HAIL WOULD BE THE MAIN THREATS IF STORMS DO DEVELOP. WILL HAVE
TO KEEP A CLOSE EYE ON THIS SCENARIO WHICH WILL DEPEND HIGHLY ON
DEGREE OF CLEARING/RECOVERY BEHIND THE MORNING CONVECTION.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 219 PM CDT THU JUL 23 2015

RIDGE OF HIGH PRESSURE DRIES THINGS OUT ON SATURDAY WITH HIGHS
CLIMBING INTO THE 80S.

SHOWER AND THUNDERSTORM CHANCES MAKE A RETURN LATER SATURDAY NIGHT
THROUGH SUNDAY NIGHT AS MODELS SHOW A WEAK MID-LEVEL TROUGH MOVING
OUT OF THE CENTRAL/NORTHERN PLAINS AND THROUGH THE UPPER MISSISSIPPI
RIVER VALLEY REGION. PLAN ON HIGHS SUNDAY AGAIN IN THE 80S.

FOR MONDAY THROUGH THURSDAY...MODELS DEPICTING A SOMEWHAT OF A
PATTERN SHIFT AS UPPER LEVEL RIDGE OF HIGH PRESSURE SHIFTS EAST AND
TROUGH OF LOW PRESSURE MOVES ACROSS THE NORTHERN PLAINS INTO THE
UPPER MISSISSIPPI RIVER VALLEY/GREAT LAKES REGION. LATEST ECMWF/GFS
SHOWING LOW PRESSURE OVER SOUTHERN CANADA PUSHING A COLD FRONT
THROUGH THE REGION MONDAY NIGHT/TUESDAY TIME FRAME FOR A CHANCE OF
SHOWERS/THUNDERSTORMS.

LOOKS LIKE SLIGHTLY COOLER CONDITIONS THEN FOR WEDNESDAY INTO
THURSDAY AS MID-LEVEL TROUGHING SETS UP ACROSS THE AREA. EXPECT QUITE A BIT OF
DAYTIME CUMULUS WITH ISOLATED SHOWERS/THUNDERSTORMS ON WEDNESDAY.
PLAN ON HIGHS WEDNESDAY IN THE 80-85 DEGREE RANGE AND IN THE UPPER
70S/LOWER 80S ON THURSDAY.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1115 PM CDT THU JUL 23 2015

THUNDERSTORMS HAVE DEVELOPED OVER THE NORTHERN PLAINS...MAKING SOME
PROGRESS EAST. LATEST MESO MODELS TAKE THIS ACTIVITY SOUTHEAST
OVERNIGHT...TRACKING ACROSS THE LOCAL AREA BETWEEN 13-18Z. PROBABLY
JUST A 3 HOUR WINDOW FOR -SHRA AT KRST/KLSE...WITH THE BETTER
CHANCES AT KRST. THE ACTIVITY IS MOVING OUT OF THE MORE FAVORABLE
UNSTABLE AIR...SO WILL KEEP TS OUT OF THE FORECAST FOR THIS MORNING.
BUFKIT SOUNDINGS SUPPORT VFR CIGS.

ANOTHER ROUND OF SHRA/TS IS POSSIBLE AS A COLD FRONT SWEEPS IN FROM
THE WEST FRI EVENING. SOME UNCERTAINTIES HERE AS WARM AIR ALOFT WILL
CAP CONVECTION INITIALLY...AND THE TIMING OF THE FRONT MOVING IN.
MESO MODELS POINT TO SCATTERED CONVECTION DEVELOPING TOWARD 00Z SAT
AROUND THE FRONT...MUCH OF WHICH COULD BE EAST OF KRST/KLSE. IF THEY
DO DEVELOP...A DECENT SHOT FOR STRONG/SEVERE STORMS. POTENTIAL FOR
BRIEF PERIOD OF MVFR WITH LATE DAY STORMS. HAVE LEFT ANY SHRA/TS
FRI EVENING MENTION OUT OF THE FORECAST FOR NOW.

&&

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

$$

SHORT TERM...DAS
LONG TERM...DAS
AVIATION...RIECK


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