884  
FXUS63 KARX 251945  
AFDARX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LA CROSSE WI  
245 PM CDT TUE JUL 25 2017  
   
SHORT TERM
 
(TONIGHT THRU WEDNESDAY NIGHT)  
ISSUED AT 245 PM CDT TUE JUL 25 2017  
 
MAIN FCST CONCERNS THIS PERIOD ARE SHRA/TSRA CHANCES LATE TONIGHT  
INTO WED EVENING AND SEVERE THREAT WITH THEM MAINLY WED  
AFTERNOON/EVENING.  
 
18Z DATA ANALYSIS HAD HIGH PRESSURE RETREATING INTO THE EASTERN  
GREAT LAKES/OH VALLEY. LOW PRESSURE WAS MOVING TOWARDS HUDSON'S BAY  
AND INTO THE CENTRAL PLAINS, WITH A FRONTAL BOUNDARY BETWEEN THE 2  
NEAR THE MN/ND BORDER. FIRST SURGE OF ROUGHLY 925-700MB MOISTURE  
TRANSPORT AHEAD OF THE PLAINS LOW HAS BEEN RESPONSIBLE FOR  
SHRA/TSRA SPREADING ACROSS MUCH OF THE FCST AREA THIS MORNING INTO  
EARLY THIS AFTERNOON. CLOUDS WITH THIS CONVECTION HAVE HELD TEMPS  
DOWN ACROSS THE AREA SO FAR TODAY, BUT CLEARING NOW WORKING IN WITH  
TEMPS LOOKING TO MAKE SOME RECOVERY TOWARD THE UPPER 70S/LOW 80S AS  
THE AFTERNOON WEARS ON.  
 
NO ISSUES NOTED WITH 25.12Z MODEL INITIALIZATIONS. SOLUTIONS SIMILAR  
AS THE MID LEVEL LOW NORTH OF LK WINNIPEG MOVES EAST ACROSS CENTRAL  
CAN TONIGHT/WED AND SHORTWAVE ENERGY OVER WY/UT/CO MOVES INTO THE  
REGION. THESE FEATURES TO MOVE EAST OF THE AREA WED EVENING, WITH  
GOOD AGREEMENT ON A SECONDARY NW FLOW SHORTWAVE TO DROP INTO  
NORTHERN MN BY 12Z THU. SHORT-TERM FCST CONFIDENCE IS GENERALLY GOOD  
THIS CYCLE.  
 
FOR THE SHORT TERM, THE MAIN LOW LEVEL WARM ADVECTION/ISENTROPIC  
LIFT AND MOISTURE TRANSPORT IS PROGGED TO SET UP WEST AND NORTH OF  
THE FCST AREA TONIGHT, MAINLY ACROSS SW MN INTO NW WI AHEAD OF THE  
COLD FRONT AS IT MOVES TO NEAR A KDLH-KOMA LINE BY 12Z WED. THIS  
EVENING TO BE DRY ACROSS MUCH OF THE FCST AREA, WITH AN INCREASE OF  
SHRA/TSRA CHANCES ACROSS THE NW SIDE AFTER MIDNIGHT AS FRONT AND  
THERMO-DYNAMIC FORCING GRADUALLY APPROACH. BIGGER CONCERN FROM ALL  
OF THIS IS THE CONVECTIVE DEBRIS CLOUDS EXPECTED TO SPREAD ACROSS  
THE FCST AREA LATER TONIGHT AND FOR WED AS THE MID/UPPER LEVEL FLOW  
BECOMES W-NW AND THE WY/UT/CO SHORTWAVE ENERGY APPROACHES. EXPECTED  
ONGOING CONVECTION WEST OF THE FCST AREA WED MORNING EXPECTED TO  
CONTINUE FEEDING THE DEBRIS CLOUDINESS, WITH WED TRENDING TO BE A  
MOSTLY CLOUDY/CLOUDY DAY. THIS TO HAVE AN IMPACT ON HOW MUCH CAPE  
CAN BUILD ACROSS THE AREA AND POTENTIAL STRONG/SEVERE TSRA CHANCES  
WED AFTERNOON/EVENING. FOR NOW, SEVERE THREAT PER SWODY2 APPEARS  
CONDITIONAL THAT SOME SUNSHINE/DIURNAL HEATING/CAPE DEVELOPMENT  
OCCURS. GREATER LIKELIHOOD OF SOME SUNSHINE WED IS OVER THE SE END  
OF THE FCST AREA, AND GIVEN TIMING OF THE FRONT ACROSS THE AREA, A  
FEW STRONG/SEVERE TSRA MAINLY SOUTH OF A KCCY-KVOK LINE, WHERE DEEP  
SHEAR WOULD BE STRONGER AND CAPE HIGHER, CANNOT BE RULED OUT. TSRA  
WED/WED EVENING WILL ALSO HAVE THE POTENTIAL TO PRODUCE LOCALLY  
HEAVY RAINS, BUT THIS THREAT MAY END UP FOCUSED SOUTH OF THE FCST  
AREA AS STRONGER OF THE LOW LEVEL MOISTURE TRANSPORT IS PROGGED  
ACROSS EAST-CENTRAL IA INTO NW IL WED AFTERNOON/EVENING. SEE HYDRO  
SECTION BELOW FOR MORE DETAILS. CONTINUED WITH 60-80% SHRA/TSRA  
CHANCES ACROSS MUCH OF THE AREA WED AFTERNOON/EVENING AS THE FRONT  
WOULD BE MOVING ACROSS THE AREA.  
 
MID LEVEL SHORTWAVE ENERGY/TROUGH AXIS AND COLD FRONT PASS WED NIGHT  
WITH DRIER/COOLER CAN HIGH PRESSURE BUILDING BEHIND THE LOW/FRONT.  
TREND OF SHRA/TSRA CHANCES DIMINISHING/ENDING FROM NW TO SE ACROSS  
THE AREA THRU THE NIGHT LOOKS GOOD. STAYED WITH A BLEND OF THE  
GUIDANCE LOWS/HIGHS FOR TONIGHT THRU WED NIGHT.  
   
LONG TERM
 
(THURSDAY THROUGH TUESDAY)  
ISSUED AT 245 PM CDT TUE JUL 25 2017  
 
FOR THU THRU FRI NIGHT: MAIN FCST CONCERN THIS PERIOD IS  
TEMPERATURES.  
 
MODEL RUNS OF 25.12Z IN GOOD AGREEMENT SWEEPING THE SHORTWAVE  
TROUGH/MID LEVEL LOW QUICKLY SE ACROSS THE WESTERN GREAT LAKES THU,  
WITH SHORTWAVE RIDGING/NW ALOFT TO FOLLOW IT FOR THU NIGHT-FRI  
NIGHT. SOME DETAIL DIFFERENCES WITH WEAK SHORTWAVES RIPPLING SE THRU  
THE FLOW THU NIGHT-FRI NIGHT, BUT THIS MORE-OR-LESS EXPECTED IN NW  
FLOW. FCST CONFIDENCE IS GOOD THIS PERIOD.  
 
SOME DETAIL DIFFERENCES ON HOW QUICKLY THE SFC LOW/COLD FRONT CLEAR  
THE AREA THU. A SMALL LINGERING CONSENSUS SHRA, PERHAPS TSRA, CHANCE  
OVER THE SE END OF THE FCST AREA EARLY THU MORNING OKAY FOR NOW.  
OTHERWISE, THIS PERIOD TO BE DOMINATED BY DRY AND SEASONABLE CAN  
HIGH PRESSURE BUILDING SE ACROSS THE REGION UNDER THE NW FLOW/  
SHORTWAVE RIDGING ALOFT. BULK OF THU THRU FRI NIGHT TRENDING TO BE A  
COUPLE OF DRY/QUIET/COMFORTABLE LATE JULY DAYS. TREND FOR SFC DEW  
POINTS TO FALL INTO THE 60S THU, THEN INTO THE 50S BY FRI AS THE  
CENTER OF THE HIGH WOULD BE OVER THE REGION LOOKS GOOD. MODEL  
SOUNDINGS SHOWING MIXING TO AROUND 850MB BOTH THU/FRI. UNDER WHAT  
SHOULD BE SUNNY/MOSTLY SUNNY SKIES, BLEND OF GUIDANCE HIGHS MOSTLY  
IN THE UPPER 70S-LOWER 80S, ABOUT A CATEGORY BELOW NORMAL, APPEAR  
WELL TRENDED AT THIS TIME.  
 
FOR SATURDAY THRU TUESDAY (DAYS 4-7): MAIN FCST CONCERNS THIS PERIOD  
ARE SMALL SHRA/TSRA CHANCES MON/TUE, TEMPERATURES THRU THE PERIOD.  
 
MEDIUM RANGE MODEL RUNS OF 25.00Z/25.12Z IN GOOD AGREEMENT ON  
WESTERN NOAM RIDGING AND EASTERN NOAM TROUGHING THRU THIS PERIOD,  
WHICH LEAVES THE UPPER MIDWEST UNDER NW FLOW ALOFT. SOME CONSENSUS  
FOR SHORTWAVE RIDGING ALOFT OVER MN/IA/WI SAT, WITH SHORTWAVE  
TROUGHS TO APPROACH/PASS SAT NIGHT THRU TUE. TYPICAL BETWEEN MODEL  
AND RUN-TO-RUN DETAIL DIFFERENCES ON THESE WAVES IN THE DAY 5-7 TIME  
FRAME. OVERALL FCST CONFIDENCE FOR NEAR TO SLIGHTLY BELOW NORMAL  
TEMPS IS ABOVE AVERAGE THIS PERIOD, BUT CONFIDENCE ON ANY SMALL  
SHRA/TSRA CHANCES DURING THE DAY 4-7 PERIOD IS BELOW AVERAGE.  
 
SAT CONTINUES TO TREND AS A DRY DAY WITH A SFC-MID LEVEL RIDGING  
OVER THE REGION. SHOULD ONE OF THE NW FLOW SHORTWAVES SPEED UP, MAY  
YET NEED A SMALL SHRA/TSRA CHANCE BY SAT AFTERNOON. BY SUN, DETAIL  
DIFFERENCES WITH THE NW FLOW SHORTWAVES IMPACT TIMING OF AND  
SHRA/TSRA CHANCES ACROSS THE FCST AREA. GIVEN LOW CONFIDENCE IN ANY  
ONE DETERMINISTIC SOLUTION, THE SMALL CONSENSUS SHRA/TSRA CHANCES SUN-  
TUE WILL HAVE TO DO.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)  
ISSUED AT 1231 PM CDT TUE JUL 25 2017  
 
SHOWERS AND EMBEDDED STORMS CONTINUE TO PUSH OFF TO THE SOUTHEAST,  
WITH A FEW ADDITIONAL SHOWERS AND STORMS EXPECTED TO IMPACT KLSE  
THROUGH THE EARLY AFTERNOON. VFR CONDITIONS THEN EXPECTED THROUGH  
THE OVERNIGHT HOURS, THOUGH A LOW LEVEL JET LOOKS TO SET UP OVER THE  
AREA TONIGHT, SO INCLUDED LLWS FROM 05Z TO 12Z AT BOTH TAF SITES.  
INCREASING CLOUD COVER AND DECREASING CEILINGS (THOUGH STILL AT VFR  
LEVELS) ARE EXPECTED THROUGH THE DAY ON WEDNESDAY. SHOWERS AND  
STORMS ARE EXPECTED TO MOVE THROUGH THE ENTIRE AREA, WITH BOTH TAF  
SITES POSSIBLY BEING IMPACTED TOWARD THE END OF THE TAF PERIOD, BUT  
CONFIDENCE ON TIMING IS NOT HIGH ENOUGH TO INCLUDE AT THIS TIME.  
SHOULD THESE SHOWERS AND STORMS ARRIVE PRIOR TO 18Z, MVFR CEILINGS  
AND VISIBILITIES WOULD BE POSSIBLE IF A STORM DIRECTLY IMPACTS  
EITHER SITE.  
 

 
   
HYDROLOGY
 
THROUGH WEDNESDAY NIGHT  
ISSUED AT 245 PM CDT TUE JUL 25 2017  
 
FLOOD WARNINGS CONTINUE ALONG THE KICKAPOO RIVER FROM SOLDIERS GROVE  
TO STEUBEN AND ALONG THE TREMPEALEAU RIVER AT DODGE. THESE LEVELS  
WILL CONTINUE TO FALL TONIGHT AND EARLY WED.  
 
FROM MAINLY LATE TONIGHT INTO WEDNESDAY EVENING, ADDITIONAL RAIN IS  
EXPECTED ACROSS THE FCST AREA. WARM CLOUD DEPTHS WILL BE NEAR OR  
ABOVE 4KM WITH PW VALUES IN THE 2 INCH RANGE, MAKING ANY TSRA  
EFFICIENT RAIN MAKERS. POTENTIAL EXITS FOR LOCALLY HEAVY RAINS FROM  
STORMS, BUT PLENTY OF DETAIL DIFFERENCES BETWEEN MODELS MAKES WHERE  
DIFFICULT TO PIN-POINT. AT THIS TIME THE GREATER THREAT OF HEAVY  
RAINS FROM TSRA IS LOOKING TO BE JUST NW OF THE FCST AREA LATE  
TONIGHT/WED MORNING, THEN ACROSS PARTS OF NE IA/SW WI WED  
AFTERNOON/EVENING. GIVEN THE PASSING LOW AND COLD FRONT, STORMS  
SHOULD BE MORE ON THE PROGRESSIVE SIDE WED/WED NIGHT, KEEPING THE  
WIDESPREAD HEAVY/EXCESSIVE RAIN THREAT ON THE LOWER SIDE.  
 
HOWEVER, IF LOCALLY HEAVY RAINS WOULD FALL ON AREAS HIT BY HEAVY  
RAINS LAST WEEK, ADDITIONAL RIVER RISES AND PERHAPS MINOR FLOODING  
WOULD BE POSSIBLE.  
 
THURSDAY THROUGH SUNDAY ARE TRENDING DRY.  
 

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

 
 

 
 
SHORT TERM...RRS  
LONG TERM....RRS  
AVIATION.....CA  
HYDROLOGY....RRS  
 
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