446
FXUS63 KARX 170622
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
122 AM CDT WED JUN 17 2026
KEY MESSAGES
- WIDESPREAD PRECIPITATION AND STORM CHANCES WEDNESDAY MORNING
PROGRESS FROM NORTHWEST TO SOUTHEAST. LOCALLY STRONGEST STORMS
FROM WESTERN THROUGH SOUTHERN PERIPHERAL COUNTIES IN SOUTHEAST
MINNESOTA AND NORTHEAST IOWA INTO SOUTHWEST WISCONSIN COULD
POTENTIALLY (15%-30%) BECOME STRONG TO SEVERE WITH LARGE HAIL
AND DAMAGING WINDS AS THE MAIN THREATS.
- LOW CONFIDENCE IN LINGERING STORM CHANCES, SOME STRONG TO
SEVERE, THROUGH THE LATE MORNING INTO EARLY AFTERNOON. A LOT
WILL DEPEND ON THE AMOUNT OF CLEARING SKIES PERMITTING LOCAL
STORM INITIATION THROUGH THE LATE AFTERNOON AND EARLY EVENING
AS LOW PRESSURE PASSES OVER THE FORECAST AREA, DRIVING
ADDITIONAL LINEAR & POTENTIALLY SCATTERED SEMI-DISCRETE
STORMS. LARGE HAIL AND DAMAGING WINDS WILL CONTINUE TO BE THE
MAIN THREATS WITH TORNADO THREAT DEPENDENT ON AMOUNT OF
DESTABILIZATION.
- LOW CONFIDENCE IN PRECIPITATION AND STORMS THURSDAY SLIGHTLY
INCREASES FOR FRIDAY AS TRANSIENT PRECIPITATION DARTS FROM
NORTHWEST TO SOUTHEAST.
DISCUSSION
ISSUED AT 121 AM CDT WED JUN 17 2026
ONGOING OBSERVATIONS & MORNING STORM THREATS:
SURFACE OBSERVATIONS TONIGHT EXHIBIT TWO AREAS OF CYCLONIC ROTATION
FROM THE CENTRAL THROUGH THE NORTHERN PLAINS, EVIDENCE OF
CYCLOGENESIS THROUGH WEDNESDAY EVENING. INTERACTION BETWEEN THESE
LOWS THROUGH THE MORNING WILL DRIVE INITIAL LOCAL PRECIPITATION AND
STORM CHANCES AS THEY CONVERGE AND MORPH INTO A ELONGATED, STRONGER
LOW BEFORE EVENTUALLY FURTHER PHASING INTO A DOUBLE-BARREL LOW BY
WEDNESDAY NIGHT.
AS THE SOUTHERN LOW PROGRESSES EAST-NORTHEAST THROUGH THE EARLY
MORNING HOURS, TIGHTENING OF THE ATTENDANT WARM SECTOR WILL AIDE IN
RAPID INTENSIFICATION OF THE COLLOCATED LOW LEVEL JET, RESULTING IN
NARROW 15-20 UBAR/S CORRIDORS OF ASCENT NEAR THE 295K ISENTROPIC
SURFACE. NOCTURNALLY ANTICYCLONIC CURVING OF THE LOW LEVEL JET AIDED
BY EAST-SOUTHEAST ADVECTION OF THE NORTHERN LOW ALONG AN ENHANCED
UPPER LEVEL JET STREAK IN GOES DERIVED UPPER LEVEL WINDS DUE TO
SYNOPTIC CONFLUENCE IN GOES WV IMAGERY LOOPS WILL RESULT IN
STRONGEST STORMS THROUGH THE EARLY MORNING HOURS ALSO SAGGING EAST-
SOUTHEAST. CURRENT TRAJECTORIES OF THIS QUICKLY INTENSIFYING AND
CHANGING PATTERN GRAZES STRONGER STORMS ALONG OUR SOUTHWESTERN
PERIPHERAL COUNTIES IN NORTHEAST IOWA AND POTENTIALLY INTO SOUTHEAST
MINNESOTA. THESE STRONGEST STORMS COULD QUICKLY BECOME SEVERE WITH
LARGE HAIL AND DAMAGING WINDS AS THE MAIN THREATS.
SEVERE STORM CHANCES THROUGH WEDNESDAY:
DETAILS (I.E., STRENGTH, TIMING, COVERAGE) SURROUNDING ADDITIONAL
SUBSEQUENT STORM CHANCES THROUGH THE REST OF WEDNESDAY DEPENDS ON
NORTHERN AND EASTERN EXTENT OF ENERGY CONSOLIDATION BETWEEN LOW
PRESSURE AREAS, EVIDENT IN DISAGREEMENT BETWEEN HIGH RESOLUTION
MODELS (17.00Z).
A MORE PHASED ORIENTATION BETWEEN LOW CENTERS THROUGH THE EARLY
MORNING BEFORE CONSOLIDATING INTO A STRONGER, ELONGATED LOW WOULD
RESULT IN A SOUTHERN SHUNT OF INCREASED MOISTURE, LIMITING /HIGHEST/
LOCAL OVERALL SEVERE THREAT (NAM/FV3 17.00Z).
HOWEVER, MORE HREF MEMBERS (HRRR/ARW 17.00Z) SOLUTIONS SUGGEST A
LESS-PHASED, MORE MERIDIONAL ORIENTATION AND INTERACTION BETWEEN
CONVERGING LOW LEVEL AREAS OF LOWER ISOHEIGHTS ALLOWING INCREASED
MOISTURE TO ADVECT FARTHER NORTH INTO THE FORECAST AREA, CAUSING
UNSTABLE AIR (1000-1500 J/KG SBCAPE) TO BIFURCATE THE SOUTHERN HALF
OF THE FORECAST AREA, INCREASING STRONG TO SEVERE STORM CHANCES
THROUGH THE AFTERNOON AND EVENING AS THE EVENTUAL LOW CENTER DRIVES
BREAKING LINEAR STORMS ACROSS THE FORECAST AREA.
ADDITIONAL STORMS THROUGH THE LATE MORNING INTO THE EARLY AFTERNOON
CANNOT BE RULED OUT AS WELL, POTENTIALLY STRONG TO SEVERE SHOULD THE
PBL RECOVER /IF/ SKIES FIND A WAY TO CLEAR IN THE WAKE OF DEPARTING
STORMS. GIVEN THE HIGHER CONFIDENCE FOR MORNING PRECIPTIATION, THIS
IS A LOWER CONFIDENCE SCENARIO BUT AVAILABLE INSTABILITY AND SHEAR
VALUES SUGGEST A SCENARIO TO REMAIN COGNIZANT OF THROUGH THE DAYTIME
HOURS.
MAIN CONCERN FOR LARGE HAIL AND DAMAGING WINDS WITH LATER STORMS AS
WELL. TORNADO RISK WILL HINGE ON AMOUNT OF CLEARING TO DESTABILIZE
THE PBL, SUBSEQUENTLY OVERCOMING ANY LINGERING INVERSION CAUSING
SBCIN/MLCIN.
LOW CONFIDENCE FOR PRECIPITATION THURSDAY:
NORTHERN EXTENT OF INCREASED MOISTURE ADVECTION THROUGH EARLY
WEDNESDAY MORNING ALSO AFFECTS PRECIPITATION CHANCES THROUGH
THURSDAY AS HREF (17.00Z) ALLUDE TO LIMITED (100-300 J/KG) OF SBCAPE
ADVECTING SOUTHEAST ALONG THE SOUTHWEST-NORTHEAST ORIENTED FRONTAL
BOUNDARY WITH MEAGER LOW LEVEL (850MB) COLD AIR ADVECTION.
THEREFORE, HAVE INCREASED A LINE OF LOW POPS (<24%) AWAY FROM NBM
BASED ON HIGH RESOLUTION SOLUTIONS ALBEIT A BIT MORE SPATIALLY AND
TEMPORALLY AGREEABLE THAN INDIVIDUAL MEMBER SOLUTIONS.
FRIDAY PRECIPITATION CHANCES:
THE TAIL END OF THE EXTENDED RIBBON OF MID LEVEL POSITIVE VORTICITY
LIFTS SLIGHTLY NORTHEAST AS THE SYNOPTIC PATTERN BEGINS TO CHANGE,
CAUSING ADDITIONAL, ALBEIT TRANSIENT, PRECIPITATION AND STORM
CHANCES TO DART ACROSS THE FORECAST AREA FOR FRIDAY. LOW CONFIDENCE
IN STORMS AS MOST (75%) MEMBERS OF EPS (16.18Z) SUGGEST 500-1000
J/KG OF MUCAPE ACROSS THE AREA WHILE GEFS (17.00Z) LIMITS SBCAPE
BELOW 500 J/KG SOMEWHERE NEAR/OVER THE FORECAST AREA. ACCOMPANYING
SHEAR VALUES WILL BE SPATIALLY LIMITED IN THE LOWER LEVELS,
PRIMARILY AND STRONGEST UNIDIRECTIONALLY IN THE MID LEVELS FROM THE
STRONGER MID TO UPPER LEVEL WINDS.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1229 AM CDT WED JUN 17 2026
VFR CONDITIONS CURRENTLY PRESENT ACROSS THE REGION. AREAS OF SHOWERS
AND STORMS ARE CURRENTLY MOVING SOUTHEAST THROUGH THE NORTHERN
GREAT PLAINS AND INTO THE MIDWEST. MOST OF THESE ARE SCATTERED
AND FAIRLY LIGHT IN NATURE WITH THE HEAVIEST ACTIVITY EXPECTED
TO REMAIN SOUTH AND WEST OF THE TERMINALS IN CENTRAL IOWA. AS
SUCH, HAVE GONE WITH SOME TEMPO GROUPS TO COVER THE SHOWER
ACTIVITY EARLY THIS MORNING. ANOTHER ROUND OF RAIN AND STORMS
WILL DEVELOP THIS AFTERNOON, THOUGH THERE IS SIGNIFICANT
UNCERTAINTY WITH THIS BATCH AS IT WILL HINGE QUITE A BIT ON THE
MORNING ACTIVITY AND HOW QUICKLY IT VACATES. THE CHANCE FOR POPS
WILL REMAIN QUITE HIGH SO HAVE GONE WITH PREVAILING SHOWERS BUT
INSTABILITY IS LESS CERTAIN SO HAVE GONE WITH PROB30S FOR THE
THUNDERSTORM COVERAGE. THE AFTERNOON PREVAILING GROUPS MAY NEED
TO BE ADJUSTED TO TEMPOS AS COVERAGE MAY BE A BIT MORE SCATTERED
IN NATURE GIVEN LATEST HI-RESOLUTION CAMS. MVFR TO IFR CIGS
WILL BUILD IN DURING THE MORNING HOURS AND CONTINUE THROUGH THE
END OF THE PERIOD WITH GENERALLY MVFR TO IFR VISIBILITIES
EXPECTED WITH BOTH BATCHES OF SHOWERS AND STORMS. RAIN WILL
START TO COME TO AN END BY LATE IN THE PERIOD, MOVING OFF TO THE
EAST AFTER 00Z. SOUTHERLY WINDS WILL PICK UP EARLY THIS MORNING
AND VEER QUICKLY TO THE WEST/NORTHWEST BEHIND A FRONTAL
BOUNDARY THAT PASSES THROUGH THIS AFTERNOON. GUSTS WILL
GRADUALLY DIMINISH INTO THE EVENING HOURS BUT SHOULD HANG ON
THROUGH THE END OF THE PERIOD.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...JAR
AVIATION...BARENDSE
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