611  
FXUS63 KARX 161115  
AFDARX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LA CROSSE WI  
615 AM CDT TUE JUL 16 2019  
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 224 AM CDT TUE JUL 16 2019  
 
MAIN FORECAST CONCERNS ARE ON THE POTENTIAL FOR STRONG THUNDERSTORMS  
THIS AFTERNOON INTO THIS EVENING WITH A THREAT FOR HEAVY RAINFALL.  
 
SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE TO DECREASE ACROSS  
THE AREA EARLY THIS MORNING AS MOISTURE TRANSPORT CONTINUES TO  
WEAKEN AND A SHORTWAVE PUSHES EAST. THERE IS ANOTHER WEAK WAVE THAT  
MOVES THROUGH THIS MORNING, SO WE MAY CONTINUE TO SEE SOME ISOLATED  
TO SCATTERED SHOWERS AND STORMS AT TIMES. FORCING THEN INCREASES  
THIS AFTERNOON INTO TONIGHT AS ANOTHER SHORTWAVE MOVES THROUGH THE  
REGION AND INTERACTS WITH A WARM FRONT/OUTFLOW BOUNDARY IN PLACE  
ACROSS THE FORECAST AREA. THE STORMS COULD DEVELOP BY EARLY  
AFTERNOON WITH RAP FORECAST SOUNDINGS SHOWING NO CAP IN PLACE BY 18Z  
TODAY WITH AROUND 2800 J/KG SURFACE BASED CAPE IN PLACE. FAIRLY WEAK  
SHEAR TODAY, WITH 0-3 KM BULK SHEAR VALUES OF 20 KTS AT BEST. THE  
MAIN THREATS FROM STORMS TODAY WILL ONCE AGAIN BE HEAVY RAINFALL  
WITH SLOW STORM MOVEMENT, PRECIPITABLE WATER VALUES OF 1.8 TO 2  
INCHES ALONG AND SOUTH OF THE INTERSTATE 90 CORRIDOR, AND WARM CLOUD  
DEPTH OF 3500 TO 4000 METERS.  
   
LONG TERM
 
(WEDNESDAY THROUGH MONDAY)  
ISSUED AT 224 AM CDT TUE JUL 16 2019  
 
MAIN FORECAST CONCERNS IN THE LONG TERM ARE ON THE POTENTIAL FOR  
DANGEROUS HEAT, AND THE POSSIBILITY OF SEVERE THUNDERSTORMS AT  
TIMES WITH A THREAT FOR HEAVY RAIN AND POSSIBLE FLASH FLOODING.  
 
A STRONGER SHORTWAVE MOVES INTO THE REGION WEDNESDAY INTO  
WEDNESDAY EVENING WITH STRONG 850 MOISTURE TRANSPORTS INCREASING  
ACROSS THE REGION. THERE IS SOME QUESTION REGARDING EARLY MORNING  
THUNDERSTORMS AND THE AMOUNT OF INSTABILITY FOR AFTERNOON AND  
EVENING STORMS, BUT THINKING WITH THE STRONG LOW LEVEL JET, THERE  
SHOULDN'T BE ANY ISSUES GETTING STORMS TO REDEVELOP. THE STORMS  
WILL BE CAPABLE OF PRODUCING VERY HEAVY RAINFALL, BUT THEY LOOK TO  
BE PROGRESSIVE. GIVEN THE POTENTIAL FOR INTENSE RAINFALL RATES  
WITH PRECIPITABLE WATER VALUES OF 2 TO 2.5 INCHES AND WARM CLOUD  
DEPTH OF 4000 TO 45000 METERS , REPEAT STORMS WOULD LEAD TO FLASH  
FLOODING CONCERNS. ALSO, THERE MAY BE ENOUGH DEEP LAYER SHEAR AND  
CAPE FOR ELEVATED SUPERCELL STRUCTURES, ESPECIALLY DURING THE LATE  
AFTERNOON AND EARLY EVENING. WILL HAVE TO KEEP A VERY CLOSE EYE  
ON THIS TIMEFRAME.  
 
HEAT AND HUMIDITY THEN BUILD ACROSS THE REGION FOR THURSDAY THROUGH  
SATURDAY WHEN 925 MB TEMPERATURES CLIMB INTO THE 28 TO 30 DEGREES C  
RANGE, WITH HIGHS LIKELY CLIMBING WELL INTO THE 90S, MAYBE A LITTLE  
HIGHER. THESE TEMPERATURES COMBINED WITH DEW POINTS IN THE LOWER  
TO MID 70S WILL RESULT IN HEAT INDEX VALUES OF 90 TO 105. WILL  
MAINTAIN THE EXCESSIVE HEAT WATCH FOR NORTHEAST IOWA AND SOUTHWEST  
WISCONSIN WHERE THE CONFIDENCE IS HIGHEST ON SEEING HEAT INDEX  
VALUES APPROACH 100 TO 105 THURSDAY THROUGH SATURDAY. IF TRENDS  
CONTINUE THE WATCH MAY NEED TO BE EXPANDED NORTHWARD. WE SHOULD  
SEE SOME RELIEF FROM THE HEAT ON SUNDAY AS A TROUGH SWINGS INTO  
THE REGION.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)  
ISSUED AT 615 AM CDT TUE JUL 16 2019  
 
FAIRLY QUIET/VFR CONDITIONS THIS MORNING BUT WILL LIKELY SEE MORE  
SHRA/TS FORMATION THIS AFTERNOON, LASTING INTO THIS EVENING. DUE  
TO SCATTERED NATURE OF THIS CONVECTION, WENT WITH VCTS AT KRST IN  
THE 19-01Z TIMEFRAME AND 21-02Z TIME FRAME AT KLSE. EXPECTING  
MAINLY VFR CONDITIONS THROUGH THE PERIOD BUT WILL BE ON THE  
LOOKOUT FOR FOG POTENTIAL TONIGHT AS WINDS BECOME LIGHT AND CLOUDS  
DISPERSE LATE IN THE EVENING/OVERNIGHT. DID NOT SOCK IN KLSE OR  
KRST AT THIS POINT IN THE TAFS BUT FOG WILL NEED TO BE ASSESSED,  
ESPECIALLY IF THERE IS ANY LOWER BOUNDARY LAYER SATURATION FROM  
CONVECTION THIS AFTERNOON/EVENING.  
 

 
   
ARX WATCHES/WARNINGS/ADVISORIES
 
 
WI...EXCESSIVE HEAT WATCH FROM THURSDAY AFTERNOON THROUGH SATURDAY  
EVENING FOR WIZ054-055-061.  
 
MN...NONE.  
IA...EXCESSIVE HEAT WATCH FROM THURSDAY AFTERNOON THROUGH SATURDAY  
EVENING FOR IAZ008>011-018-019-029-030.  
 

 
 

 
 
SHORT TERM...WETENKAMP  
LONG TERM...WETENKAMP  
AVIATION...DAS  
 
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