128
FXUS63 KARX 161833
AFDARX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
135 PM CDT TUE SEP 16 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 /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1227 PM CDT TUE SEP 16 2025
LOW CONFIDENCE VFR FORECAST OVER THE NEXT 24 HOURS AS LOW
PROBABILITIES (10-25%) FOR ISOLATED TO SCATTERED SHOWERS/STORMS
PERSIST THROUGHOUT THIS AFTERNOON AND EARLY EVENING. MVFR TO IFR
VSBY REDUCTIONS WILL BE POSSIBLE WITH ANY SHOWERS OR STORMS WITH THE
MAIN POINT OF UNCERTAINTY RESULTING FROM EXACT LOCATION OF WHERE
THEY MAY DEVELOP. AS WE HEAD INTO THE OVERNIGHT AND EARLY WEDNESDAY
MORNING, THERE IS SOME POTENTIAL FOR VALLEY FOG ALONG THE
MISSISSIPPI AND WISCONSIN RIVERS AS WELL AS THEIR TRIBUTARIES WITH
LIGHT SURFACE WINDS OF UNDER 5 KTS AND SOME PROBABILITIES IN THE NBH
FOR MVFR VSBYS AT LSE. HOWEVER, GIVEN UNCERTAINTY WITH UPPER-LEVEL
CLOUD TRENDS AND ON SOME SLIGHTLY STRONGER WINDS JUST OFF THE DECK
IN THE RAP/HRRR SOUNDINGS, HAVE OPTED TO LEAVE OUT ANY FOG MENTION
FOR KLSE AT THIS TIME. ADDITIONAL SHOWERS AND STORMS WILL BE
POSSIBLE (15-30% CHANCE) DURING THE LATE MORNING WEDNESDAY AND
CONTINUING UNTIL AFTER 18Z.
ARX WATCHES/WARNINGS/ADVISORIES
WI...NONE.
MN...NONE.
IA...NONE.
DISCUSSION...RIECK
AVIATION.....NAYLOR
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