Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 242237
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
535 PM CDT FRI JUL 24 2015

.SHORT TERM...(TODAY THROUGH SATURDAY NIGHT)
ISSUED AT 207 PM CDT FRI JUL 24 2015

IMMEDIATE CONCERN IS SEVERE CONVECTION POTENTIAL THIS EVENING WITH
COLD FROPA.

SURFACE MAP THIS AFTERNOON SHOWS THE COLD FRONT EXTENDING FROM THE
ARROWHEAD OF MN THROUGH NORTHWEST WI INTO SOUTHEAST MN INTO NORTH
CENTRAL IA. RAP PUSHES CORRIDOR OF 0-1KM MUCAPE IN THE 1500-3000J/KG
RANGE (NE-SE RESPECTIVELY) ALONG THE FRONT AS IT MOVES INTO THE AREA
BY 7PM. HOWEVER...RAP/NAM SOUNDING CONTINUE TO SHOW A STRONG 700-
800MB CAP IN PLACE TO INHIBIT SURFACE BASED CONVECTION. THE ONLY
MODEL SHOWING CONVECTIVE REFLECTIVITY OUTPUT WITH THE FROPA IS THE
NAM...BUT THIS IS WITH MUCH HIGHER PROGGED DEW POINTS IN THE 75-80
DEGREE RANGE WHICH SEEMS A BIT OVERDONE. AS A RESULT...CONVECTION
ALONG THE FRONT WILL BE VERY CONDITIONAL DUE TO THE CAP IN PLACE. IF
THE CAP DOES WEAKEN SOME...SCATTERED STRONG TO SEVERE STORMS COULD
FIRE WITH LARGE HAIL AND DAMAGING WINDS BEING THE MAIN THREAT. AS A
RESULT OF THE CONDITIONAL NATURE TO THIS SCENARIO...KEEPING POP
CATEGORY IN THE CHANCE RANGE...WITH HIGHER PROBABILITIES OVER THE
EAST WHERE CAP WILL BE WEAKEST. LOOK FOR STORM THREAT TO SUBSIDE
AFTER MIDNIGHT AS THE FRONT EXITS THE AREA.

SATURDAY LOOKS LIKE A DRIER DAY AS HIGH PRESSURE/SUBSIDENCE TAKES
CONTROL ACROSS THE AREA. PLAN ON HIGHS IN THE 80S.

SHOWER/THUNDERSTORM CHANCES RETURN LATE SATURDAY NIGHT/AFTER
MIDNIGHT AS A SHORTWAVE TROUGH ROUNDS THE TOP OF THE HEAT RIDGE IN
PLACE ACROSS THE PLAINS. NAM MOST AGGRESSIVE WITH THIS FEATURE WHILE
THE ECMWF IS MUCH WEAKER AND FARTHER SOUTH. WILL GO WITH 20-40 PPS
FOR NOW AND MAINLY WEST OF THE MISSISSIPPI RIVER.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 207 PM CDT FRI JUL 24 2015

LOOK FOR THAT MID-LEVEL TROUGH TO CONTINUE PUSHING EAST INTO/THROUGH
THE AREA SUNDAY INTO SUNDAY NIGHT FOR A CONTINUED CHANCE OF
SHOWERS/THUNDERSTORMS. THIS CONVECTION LOOKS TO BE SUB-SEVERE AT
THIS TIME WITH JUST LIGHTNING AND SOME HEAVY DOWNPOURS BEING THE
MAIN IMPACTS. OTHERWISE...LOOK FOR HIGHS IN THE LOWER TO MIDDLE 80S.

MONDAY HOLDS A LOWER-END CHANCE FOR SOME AIRMASS SHOWERS AND
THUNDERSTORMS AS THERE WILL STILL BE A SLIGHT WEAKNESS IN THE HEAT
RIDGE IN PLACE AS HIGHS TOP OFF WELL INTO THE 80S.

FOR MONDAY NIGHT THROUGH TUESDAY...THE REGION WILL BE IN AN AREA OF
WARM AIR ADVECTION/ISENTROPIC LIFT AHEAD OF LOW PRESSURE CROSSING
THE NORTHERN PLAINS. THIS WILL SPREAD MORE SHOWER/THUNDERSTORM
CHANCES INTO THE AREA. HIGHS ON TUESDAY LOOKS LIKE THEY COULD TOP
90S DEGREES AT SOME LOCATIONS. THEN FOR TUESDAY NIGHT INTO
WEDNESDAY...A COLD FRONT WILL MOVE ACROSS THE AREA FOR A CONTINUED
CHANCE OF SHOWERS AND STORMS.

THURSDAY LOOKS TO BE DRY AS A WEAK RIDGE OF HIGH PRESSURE
ESTABLISHES ITSELF OVER THE REGION. OTHERWISE...PLEASANT WITH HIGHS
IN THE UPPER 7S0 TO THE LOWER 80S.

SMALL-END SHOWER/THUNDER CHANCE RETURN ON FRIDAY AS BOTH THE
GFS/ECMWF SHOW A TROUGH/COLD FRONT MOVING ACROSS MN INTO NORTHWEST
WI. LOOK FOR TEMPERATURES AGAIN IN THE UPPER 70S/LOWER 80S.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 535 PM CDT FRI JUL 24 2015

ATMOSPHERE HAS DESTABILIZED...WITH INCREASING CAPE AND FAVORABLE
WIND SHEAR THAT COULD HELP FUEL/ORGANIZE ANY STORMS THAT DEVELOP.
HOWEVER...STRONG LOW LEVEL CAPPING INVERSION IN PLACE AT THE TAF
SITES...AND THE APPROACHING COLD FRONT DOES NOT LOOK OVERLY
CONVERGENT. MESO MODELS ARE NOT FAVORING SHRA/TS DEVELOPMENT ALONG
THE SOUTHERN FLANKS OF THE FRONT...COMING THROUGH WITH SOME VFR-MVFR
CLOUDS AND A WIND SHIFT. KLSE WOULD HAVE THE BEST SHOT...AND THAT
LOOKS MEAGER AT THE MOMENT. WILL KEEP TAFS RAIN FREE FOR THE
MOMENT...AND ADD MENTION IF RADAR TRENDS NECESSITATE IT.

FRONT LOOKS TO SLIDE ACROSS KRST NEAR 03Z AND KLSE NEAR 05Z. LOOK
FOR WIND TO GO WEST THEN NORTH. EXPECTING VFR CONDITIONS OVERNIGHT
THROUGH SAT.

&&

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

$$

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



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