846
FXUS63 KARX 170551
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1251 AM CDT WED SEP 17 2025
KEY MESSAGES
- A GRADUAL INCREASE IN RAIN CHANCES, AREAL COVERAGE, AS WE MOVE INTO
THE WEEKEND.
- SUMMERY TEMPS PERSIST INTO THURSDAY (80+ HIGHS FOR MOST), DROPPING
TO MORE SEASONABLE LEVELS FOR THE WEEKEND (70S).
DISCUSSION
ISSUED AT 135 PM CDT TUE SEP 16 2025
> OVERVIEW: GEFS AND EPS CONTINUE TO FAVOR A SLOWER, RETROGRADING
UPPER LEVEL FLOW FOR THE NEXT FEW DAYS - BUILDING THE BENT OVER
RIDGE (ACROSS THE EASTERN GREAT LAKES) WESTWARD AS SHORTWAVES DROP
SOUTH OUT OF CANADA INTO THE PLAINS TROUGH. THE RIDGE EASES EAST
OVER THE WEEKEND AS THE TROUGH GETS A PUSH FROM A SERIES OF
SHORTWAVES MOVING OUT OF THE PAC NW/WESTERN CANADA.
LONG RANGE GUIDANCE ALSO CONTINUES TO HINT AT A MORE DEVELOPED
SHORTWAVE TROUGH/COLD FRONT TO TRACK FROM CANADA TO ACROSS PORTIONS
OF THE REGION MON/TUE. SOME DIFFERENCES IN TIMING/LOCATION - BUT HAS
THE POTENTIAL TO PACK MORE OF A PUNCH.
> TEMPERATURES: THE SUMMER TEMPS PERSIST THROUGH AT LEAST THU WITH
80+ DEGREE HIGHS PROGGED IN THE GRAND ENSEMBLE FOR MOST OF THE LOCAL
AREA. SOME TEMPERING WHERE/IF PCPN DEVELOPS - WITH LOW POPS HOLDING
MOSTLY WEST OF THE MISSISSIPPI RIVER AND NORTH OF I-94.
CLOUDS AND MORE WIDESPREAD SHOWERS WILL BE USHERED IN WITH THE UPPER
LEVEL LOW/TROUGH FOR THE WEEKEND WHILE COOLER AIR FOLLOWS IN THE
WAKE OF THE LOW. IT'S NOT A BIG DROP OFF BUT HIGHS BACK INTO THE
70S, MORE SEASONABLE FOR MID SEP, ARE CURRENTLY EXPECTED. AGAIN,
WHERE MORE RAIN IS REALIZED TEMPS WILL HOLD A FEW DEGREES COOLER
(60S FOR HIGHS CERTAINLY POSSIBLE).
> RAIN CHANCES: WEAK UPPER LEVEL SHORTWAVE AND DIFFERENTIAL HEATING
WORKING WITH 1.5-2+ K J/KG MUCAPE TO FIRE SCATTERED SHOWERS/STORMS
ACROSS CENTRAL IA, BUILDING NORTHEAST. THIS SHOULD CONTINUE THROUGH
LATE AFTERNOON, DIMINISHING IN THE EVENING WITH THE LOSS OF DAYTIME
HEATING. LOCALLY NE IA LIKELY TO BE IMPACTED BY SOME CONVECTION. HOW
FAR NORTH/NORTHEAST OF THAT IS NOT CERTAIN. EXPECT SOME UPDATES TO
RAIN CHANCES WITH FOCUS ON NEAR TERM TRENDS.
WED COULD BE SIMILAR TO TODAY WITH LINGERING, WEAK MICRO SCALE
BOUNDARIES, RIBBON OF INSTABILITY, AND CONVECTIVE INDUCED/ENHANCED
AREAS OF UPPER LEVEL DIVERGENCE PROVIDE SOME LIFT FOR SCATTERED
SHOWERS/STORMS. A LOT OF UNCERTAINTY WITH HOW RAIN CHANCES
COULD/WILL LAYOUT - WITH A CLOSE EYE ON ENVIRONMENT/NEAR TERM TRENDS
LEADING TO ADJUSTMENTS TO THE FORECAST. WILL LEAN INTO THE NBM FOR
CHANCES FOR NOW, WHICH HOLD MOST WEST OF THE MISSISSIPPI RIVER/NORTH
OF I-94 (INFLUENCE OF THE RIDGE HOLDING SPREADING CHANCE FURTHER
EAST/SOUTHEAST). THU COULD BE A REPEAT OF WED.
RAIN CHANCES WILL BE ON THE INCREASE AS THE AREA COMES MORE DIRECTLY
UNDER THE INFLUENCE OF THE UPPER LEVEL LOW/TROUGH. MUCH OF FRI
THROUGH SUN THEN LOOKS SHOWERY - PERHAPS MORE SO FRI/SAT. MIGHT GET
A 24 HOUR BREAK FROM THE RAIN BEFORE ANOTHER SHORTWAVE TROUGH SLIDES
ACROSS/NEAR THE AREA MON/TUE.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1208 AM CDT WED SEP 17 2025
PERSISTENT LOW CONFIDENCE (<30%) IN FLIGHT IMPACTS THROUGH THE
17.06Z TAF PERIOD ACROSS THE FORECAST AREA FROM SOUTHEAST
MINNESOTA, NORTHEAST IOWA, AND SOUTHWEST THROUGH CENTRAL
WISCONSIN. LOW STORM CHANCES (20-30%) INITIALLY AFFECT AIRPORTS
WEST OF THE MISSISSIPPI RIVER VALLEY (KAUM/KCCY) THROUGH THE
MORNING HOURS, SPREADING EAST BY LATE MORNING. IFR VISIBILITIES
LIKELY WHERE STORMS FORM SHOULD THEY PASS OVER ASOS/AWOS.
THURSDAY THROUGH SUNDAY..STORM CHANCES INCREASE AND SPREAD EAST
THURSDAY, BECOMING WIDESPREAD FRIDAY AND LINGERING THROUGH THE
WEEKEND.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...RIECK
AVIATION...JAR
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