754
FXUS63 KARX 171848
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
148 PM CDT WED SEP 17 2025
KEY MESSAGES
- SCATTERED SHOWERS AND THUNDERSTORMS THROUGH THE WEEKEND WITH
INCREASING COVERAGE HEADING TO THE WEEKEND.
- WARMER TEMPERATURES CONTINUE THROUGH THURSDAY WITH HIGHS
MAINLY IN THE 80S, THEN DROP INTO THE 70S THROUGH EARLY NEXT
WEEK.
DISCUSSION
ISSUED AT 148 PM CDT WED SEP 17 2025
SHOWER AND STORM CHANCES THROUGH THE WEEKEND:
AN UPPER-LEVEL LOW WILL CONTINUE TO SPIN OVER THE NORTHERN PLAINS
TODAY AND FRIDAY. AS IT DOES SO, VARIOUS SHORTWAVE IMPULSES WILL
IMPACT THE UPPER MIDWEST. THIS WILL INCREASE RAIN CHANCES AND
COVERAGE OF RAIN CHANCES THROUGH THE WEEKEND, AS THE LOW GRADUALLY
SHIFTS EASTWARD. FOR TODAYS CONVECTION, WHILE A COUPLE BANDS OF
SHORTWAVE ENERGY MOVES OVER THE AREA, THERE IS ALSO SOME
VORTICITY ADVECTION WITH DIFFLUENCE ALOFT AND COMBINING THIS
WITH 500 TO 1250 J/KG OF MLCAPE, SHOWERS AND STORMS FORMED THIS
MORNING AND WILL CONTINUE TO DO SO THROUGH THE AFTERNOON. BY
THIS EVENING, ANOTHER SHORTWAVE IMPULSE ARRIVES AND WILL HELP TO
KEEP RAIN CHANCES ONGOING THROUGH THE OVERNIGHT. AS THE LOW
SHIFTS EASTWARD THROUGH THE WEEKEND, RAIN CHANCES WILL CONTINUE.
ANOTHER THING TO LOOK AT IS MOISTURE TRANSPORT, WHICH DESPITE
WEAK FLOW ALOFT, DOES HAVE A SIGNAL LINGERING THROUGH THE
WEEKEND AS THESE SHORTWAVES PUSH THROUGH THE REGION. THIS ADDS
TO THE CONFIDENCE OF SHOWERS AND STORMS CONTINUING TO BE
POSSIBLE.
SEVERE STORM POTENTIAL, WHILE QUITE LOW, CANNOT BE RULED OUT. THERE
WERE SOME HAIL REPORTS YESTERDAY, HOWEVER THE MID-LEVEL LAPSE RATES
WERE HIGHER (CLOSER TO 7 C/KM) WHEREAS TODAY AND THURSDAY THEY WILL
BE CLOSER TO 6 C/KM. THERE WAS ALSO HIGHER AMOUNTS OF INSTABILITY
YESTERDAY COMPARED TO TODAY. WITH PWATS MOSTLY RANGING BETWEEN 1.25
TO 1.5" AND STORM MOTIONS BEING QUITE SLOW DUE TO THE WEAK
ALOFT, THE MAIN POTENTIAL HAZARD WOULD BE LOCALIZED HEAVY RAINFALL.
UNCERTAINTY FOR EARLY NEXT WEEK:
ENSEMBLE AND DETERMINISTIC GUIDANCE ARE DISAGREEING ON WHAT WILL
TRANSPIRE NEXT WEEK. BOTH THE DETERMINISTIC GFS AND EC HAVE A LOW
THAT COMES DOWN FROM CANADA AND THEN DEEPENS OVER THE NORTHERN
PLAINS. THE CMC DOES NOT HAVE THIS BUT RATHER HAS A SHORTWAVE THAT
MOVES THROUGH EARLY NEXT WEEK WITH THE LONGWAVE TROUGH STAYING NORTH
OF THE US BORDER. ENSEMBLE CLUSTER ANALYSIS HAS DISAGREEMENTS ON THE
STRENGTH AND LOCATION OF THE LONGWAVE TROUGH. THIS WILL BE SOMETHING
TO WATCH AS THIS COULD BRING COOLER TEMPERATURES, INCREASED
PRECIPITATION CHANCES, OR WINDY CONDITIONS.
TEMPERATURE FORECAST:
TODAY IS THE LAST DAY FOR LOCATIONS TO BE IN THE LOW TO MID 80S. BY
FRIDAY, HIGHS ARE IN THE LOW TO MID 70S. DEPENDING ON WHAT HAPPENS
NEXT WEEK, TEMPERATURES ARE CURRENTLY FORECASTED TO BE IN THE MID TO
UPPER 70S. LOW TEMPERATURES START OUT IN THE LOW 60S FOR TONIGHT AND
THURSDAY, THEN GRADUALLY DECREASE TOWARDS THE MID TO UPPER 50S BY
EARLY NEXT WEEK.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 100 PM CDT WED SEP 17 2025
A SIMILAR FORECAST TO DAYS PREVIOUS PRESENTS ITSELF FOR THE NEXT 24
HRS AS SMALL SCALE FORCING MECHANISMS WILL RESULT IN LOW CHANCES FOR
SHOWERS/STORMS THIS AFTERNOON AND EVENING. CURRENTLY KEEPING WITH A
DRY FORECAST AT KLSE AND EAST OF THE MISSISSIPPI RIVER. HOWEVER,
WITH AN ONGOING AXIS OF MOISTURE TRANSPORT PUSHING AN AREA OF
SHOWERS/STORMS INTO SOUTHEAST MN, HAVE INCLUDED A TEMPO FOR -SHRA AT
KRST FOR MUCH OF THE AFTERNOON. AS WE HEAD INTO THE OVERNIGHT, A
WEAK MESOSCALE LOW PUSHES NORTHEAST INTO THE REGION AS DEPICTED BY
SOME OF THE CAMS. CONSEQUENTLY, HAVE INCLUDED A PROB30 AT KRST AS
THIS IS THE ONLY OTHER TANGIBLE FEATURE ACROSS SHORT-TERM GUIDANCE
OUTSIDE OF ONGOING CONVECTION. THE EASTERN EXTENT FOR OVERNIGHT
RAINFALL REMAINS SOMEWHAT UNCERTAIN WITH SOME WEAK DRIER LOW-LEVEL
EASTERLY FLOW SO HAVE OPTED TO LEAVE OUT ANY MENTION AT KLSE FOR
NOW. VALLEY FOG APPEARS UNLIKELY TONIGHT AT KLSE AND OTHER VALLEY
LOCATIONS DUE TO CLOUD COVER OVERHEAD EVEN IF SFC WINDS ARE CALM
WITH SOME DEPTH TO THE LIGHT WIND LAYER.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...CECAVA
AVIATION...NAYLOR
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