677  
FXUS63 KARX 020816  
AFDARX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LA CROSSE WI  
316 AM CDT FRI JUN 2 2023  
   
DISCUSSION
 
(TODAY THROUGH THURSDAY)  
ISSUED AT 216 AM CDT FRI JUN 2 2023  
 
KEY MESSAGES:  
 
- SCATTERED STORM CHANCES CONTINUE TODAY & SATURDAY INTO SUNDAY  
 
- ANOMALOUSLY WARM TEMPERATURES CONTINUE TODAY & THROUGH THE  
WEEKEND  
 
- MORE WIDESPREAD PRECIPITATION POTENTIAL INTO THE NEW WORK WEEK  
WITH POTENTIAL PATTERN SHIFT THROUGH LATTER HALF OF THE WEEK  
 
STORM CHANCES TODAY & TONIGHT:  
 
WATER VAPOR SATELLITE THIS MORNING SHOWS AN ESTABLISHED UPPER  
LEVEL RIDGE OVER THE GREAT LAKES REGION WITH A WESTWARD EXPANSION  
INTO THE UPPER MISSISSIPPI RIVER VALLEY. THIS HAS PUSHED THE  
CORRIDOR FOR NORTHWARD MOVING SHORT WAVE TROUGHS OVER THE PLAINS  
INTO THE MISSOURI RIVER VALLEY LEAVING THE LOCAL REGION LARGELY  
ABSENT FOR FOCUS OF CONVECTION DEVELOPMENT. SOME WEAK WARM AIR  
ADVECTION WILL CONTINUE OVER THE AREA ON THE WESTERN FRINGES OF  
THE LOW LEVEL RIDGE AXIS TO PRODUCE SOME WEAK ISENTROPIC UP GLIDE  
AND HELP AID IN THE DEVELOPMENT OF MORE DIURNAL SHOWERS AND STORMS  
DURING THE AFTERNOON AND EARLY EVENING. THIS ACTIVITY COULD POP  
UP ALMOST ANYWHERE ACROSS THE AREA, BUT MAY HAVE BIT BETTER CHANCE  
FOR HIGHER COVERAGE ACROSS NORTHEAST IOWA AND SOUTHEAST MINNESOTA  
INTO NORTH-CENTRAL WISCONSIN COINCIDING WITH AN AXIS OF HIGHER  
MLCAPE TO 1000 J/KG ACCORDING TO THE RAP. WITH NO SHEAR OVER THE  
AREA, THE ACTIVITY WILL STAY DISORGANIZED AND LIKELY NOT PERSIST  
FOR VERY LONG BEFORE THE CORES COLLAPSE. WITH PRECIPTABLE WATER  
AMOUNTS OF 1.25 TO 1.75 INCHES, SOME LOCALLY HIGHER RAINFALL  
TOTALS COULD OCCUR DUE TO WHAT SHOULD BE SLOW MOVING CELLS. SOME  
GUSTY WINDS WILL ALSO BE POSSIBLE AS THE CELLS DISSIPATE FROM THE  
COLLAPSING CORES. LOOK FOR THE COVERAGE OF ANY CONVECTION THAT  
DOES DEVELOP TO DIMINISH FAIRLY QUICKLY DURING THE EVENING WITH  
THE LOSS OF DAYTIME HEATING.  
 
WEEKEND SYNOPTIC SETUP & ANOMALOUSLY WARM SURFACE TEMPERATURES:  
 
ANOMALOUSLY WARM TEMPERATURES ARE EXPECTED TO CONTINUE THROUGH  
THE WEEKEND WITH LITTLE CHANGE IN THE SYNOPTIC SETUP. STRONG  
MULTI-ENSEMBLE CONFIDENCE (80-100%) SURROUNDS MID/UPPER LEVEL  
HIGHER HEIGHTS SITUATED OVER THE NORTHERN PLAINS. THE GEFS  
(02.00Z) HAS REBOUNDED ITS CONFIDENCE (70-100%) OVER THE LAST FEW  
RUNS FOR THE 80 DEGREE ISOTHERM AFFECTING MUCH OF THE AREA  
SATURDAY, SHIFTING SLIGHTLY WEST SUNDAY PRIMARILY AFFECTING WEST  
OF THE MISSISSIPPI RIVER. EPS (02.00Z) HAS CONTINUED 100%  
CONFIDENCE OVER SEVERAL PREVIOUS RUNS FOR THE 80 DEGREE ISOTHERM  
ENVELOPING THE ENTIRETY OF THE UPPER MISSISSIPPI RIVER VALLEY.  
THEREFORE, SIMILAR TO PREVIOUS FORECASTS IN COLLABORATION WITH  
NEIGHBORS, HAVE SLIGHTLY BUMPED MAXIMUM DAYTIME TEMPERATURES AWAY  
FROM DETERMINISTIC NATIONAL BLEND GUIDANCE USING 50TH PERCENTILE  
NATIONAL BLEND PROBABILISTIC GUIDANCE. SPREAD BETWEEN THE TWO HAS  
GREATLY DECREASED WITH THE MOST DETERMINISTIC MEMBERS ALIGNING  
TOWARDS THE 50TH PERCENTILE IN THE VIOLIN PLOT, PROVIDING  
INCREASED CONFIDENCE.  
 
SATURDAY STORM SETUP & FORECAST DIFFERENCES:  
 
ALSO SIMILAR TO PREVIOUS FORECASTS, THE EXACT LOCATION OF THE  
AFOREMENTIONED HIGHER GEOPOTENTIAL HEIGHTS WILL DETERMINE  
PRECIPITATION CHANCES THIS WEEKEND INTO EARLY NEXT WEEK. UNLIKE  
PREVIOUS FORECASTS, SHORT TERM HIGH RESOLUTION MODELS HAVE BEGUN  
TO PICK UP THE SATURDAY AFTERNOON-EVENING FORECAST HOUR, WHICH  
HAS PREVIOUSLY BEEN CRUCIAL FOR RESOLVING CONVECTION THIS PAST  
WEEK WITHIN THIS PATTERN; ESPECIALLY WHEN COMPARED TO THE OVERLY-  
SATURATED AND DISAGREEING LONG TERM GLOBAL MODELS. UNFORTUNATELY,  
DISAGREEMENT BETWEEN SHORT TERM MODELS ALSO ABOUNDS, RESULTING IN  
BINARY HREF CONFIDENCE (I.E., YES/NO) AND LIMITING ITS OVERALL  
USEFULNESS. THEREFORE, THIS FORECASTER HAS RESORTED TO A LENGTHY  
DISCUSSION OF THE HIGH RESOLUTION DIFFERENCES AND IMPACTS:  
 
SYNOPTICALLY, DISAGREEMENT STEMS FROM THE AFOREMENTIONED  
PERTURBATION SLIDING ALONG THE EASTERN PERIPHERY OF THE UPPER  
LEVEL HIGHER HEIGHTS AND THE RESULTANT USHERING IN OF A LOW LEVEL  
DRY PUNCH; VARYING IN MAGNITUDE FROM 43 TO 60 DEGREE FORECASTED  
SURFACE DEWPOINT TEMPERATURES. THE RAP/HRRR (02.03/06Z) HAS THE  
DRIEST SOLUTION WITH 43 DEGREE MINIMA DEWPOINTS ADVECTING WEST  
ACROSS THE FORECAST AREA SATURDAY AFTERNOON. THIS LIMITS MLCAPE  
TO AREAS WEST OF MISSISSIPPI RIVER WHILE POTENTIALLY PROVIDING  
FORCING. IT APPEARS THESE MODELS AND THERE PBL SCHEMES ARE TOO  
MIXED AND SHOULD THEREFORE BE TAKEN WITH A GRAIN OF NACL. ON THE  
OTHER END OF THE SPECTRUM, THE NSSLWRFARW/FV3 (02.00Z) DO NOT  
ADVECT DRY AIR THIS FAR WEST AND KEEP DEWPOINTS IN THE UPPER 50S  
TO LOW 60S. THIS RESULTS IN A SOLUTION SIMILAR TO TODAY AND  
THURSDAY WITH A LACK OF FORCING OUTSIDE OF DIURNAL-INFLUENCED  
INSTABILITY, AN OVERALL MORE WIDESPREAD MLCAPE POOL, AND SCATTERED  
STORMS THAT INCREASE IN COVERAGE OUTSIDE OF THE LOCAL AREA.  
BETWEEN THESE SOLUTIONS LIES THE ARW (02.00Z) WITH MID TO LOW 50  
DEGREE DEWPOINTS AND AN AXIS OF GREATER THAN 1000 J/KG MLCAPE AND  
ACCOMPANYING STORMS ADVECTING THROUGH THE FORECAST AREA SATURDAY  
AFTERNOON-EVENING.  
 
SATURDAY STORMS POTENTIAL IMPACTS:  
 
IN SUMMARY, WHILE SHORT TERM MODELS HAVE BEGUN TO PICK UP SATURDAY'S  
PRECIPITATION POTENTIAL, DISAGREEMENTS ABOUND. LONGER RANGE  
GLOBAL MODELS CONTINUE THE TRENDS THEY HAVE HAD ALL WEEK, WITH  
THE GEFS/GFS (02.00Z) BEING THE WETTER SOLUTION, FARTHER WEST WITH  
THE HIGHER HEIGHTS THAN THE DRY-SOLUTION EPS (02.00Z). AGREEMENT  
DOES REACH SEVERITY WITH LITTLE TO NO SHEAR AT NEARLY ALL LEVELS  
IN ALL HIGH RESOLUTION CAMS. GIVEN THE PREVIOUS LENGTHY DESCRIPTION  
OF DIFFERENCES IN MOISTURE OF INCOMING AIR MASS, HAVE REDUCED  
SURFACE DEWPOINT TEMPERATURES FOR SATURDAY USING THE ARW (02.00Z).  
WHILE THE DEPTH AND MAGNITUDE OF THE PBL DRY AIR IS IN  
DISAGREEMENT BETWEEN HIGH RESOLUTION MODEL SOUNDINGS, THEY DO  
AGREE ON DIFFERING MAGNITUDES OF A LOW LEVEL INVERTED V.  
THEREFORE, STRONG WINDS POSSIBLE WITH STORMS AS CORES COLLAPSE.  
 
NEW WEEK PRECIPITATION CHANCES & POTENTIAL PATTERN CHANGE:  
 
THE UPPER LEVEL PATTERN EXPECTED TO REMAIN IN PLACE FOR THE START  
OF THE NEW WORK WEEK WITH LACKLUSTER CONFIDENCE (40-70%) FOR  
GREATER THAN A TENTH OF RAINFALL (GEFS/EPS 02.00Z). MOST  
WIDESPREAD PROBABILISTIC PRECIPITATION PROBABILITIES SWING  
THROUGH THE UPPER MISSISSIPPI RIVER VALLEY MONDAY INTO TUESDAY  
FROM ANOTHER QUASI-ZONAL WOBBLE ALONG THE EASTERN PERIPHERY OF  
INCREASED UPPER LEVEL HEIGHTS. HAVE CONTINUED WITH NATIONAL BLEND  
POPS WHICH PROVIDES "CHANCE" FOR STORMS. THROUGH MIDWEEK, HIGH  
CONFIDENCE (80-100%) FOR THE UPPER LEVEL HIGH NOW OVER THE CENTRAL-  
NORTHERN PLAINS REDUCING STRENGTH. THIS IS EVIDENT IN PROBABILITIES  
FOR 582 DAM ISOHEIGHTS AT 500 MB ADVECTING SOUTH JOINING THE MEAN  
FLOW OVER THE SOUTHERN UNITED STATES. CONFIDENCE IN PLACEMENT OF  
THE 576 DAM ISOHEIGHT AT 500 MB WAVERS BETWEEN AND WITHIN RUNS OF  
LONG TERM GLOBAL MODELS. GENERAL CONSENSUS FOR THE UPSTREAM RIDGE  
TO SLOWLY RETROGRADE THROUGH THE WEEK, PLACING THE LOCAL AREA ON  
THE EASTERN PERIPHERY WITHIN NORTHWEST FLOW. THEREFORE, COULD BE  
A CHANGE IN THE OVERALL PATTERN AND PRECIPITATION CHANCES.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)  
ISSUED AT 1030 PM CDT THU JUN 1 2023  
 
VFR CONDITIONS EXPECTED TO CONTINUE THROUGH THIS TAF PERIOD.  
ANTICIPATE ANOTHER AFTERNOON OF SCATTERED POP UP SHOWERS AND  
STORMS AFTER 19Z FRIDAY. WEAK FORCING AND LIMITED MOISTURE LEADS  
TO LOWER CONFIDENCE IN WHETHER THESE MAY SPECIFICALLY IMPACT  
THE TERMINALS, SO HAVE TRIED TO CONFINE VCTS TO THE FAVORED  
AFTERNOON - EARLY EVENING HOURS. LOCALIZED HEAVY RAIN, BRIEF  
VISIBILITY REDUCTIONS, AND SOME GUSTY WINDS WOULD BE POSSIBLE.  
 

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

 
 

 
 
DISCUSSION...04/JAR  
AVIATION...KURZ  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab WI Page
The Nexlab IA Page
The Nexlab MN Page Main Text Page