FXUS63 KARX 041829

AFDARX



Area Forecast Discussion

National Weather Service La Crosse WI

129 PM CDT Tue Aug 4 2026



.KEY MESSAGES...



- Showers and maybe a rumble of thunder south of I-90 this

  afternoon and tonight. Rainfall amounts increase as one

  travels south, with little for accumulation near I-90 to

  1/2"-1" south of Highway 18. 



- Cooler through Wednesday, warming back to around seasonable 

  temperatures for the weekend.



- Risk for showers and storms returns for the weekend, but

  confidence in the timing and placement of any showers remains

  low (20-40% chance).



&&



.DISCUSSION...

Issued at 125 PM CDT Tue Aug 4 2026



This Afternoon - Wednesday Morning: Periodic Rain and Storms



The line of showers and storms along a cold front that moved 

out of central MN early this morning faded by 9am as the 

attendant upper wave lifted into SW Ontario. The upcoming rain 

focus shifts to mainly south of I-90 for this afternoon and 

tonight as the lower tropospheric baroclinic zone/theta-e axis 

sags into Iowa and far southern Wisconsin (with convergence 

strongest in Iowa) and the right-rear quadrant of the upper 

level jet arrives. 



Upstream radar trends over Nebraska and western Iowa continue 

to support that the highest rainfall amounts will be south of 

the forecast area, with lighter stratiform precipitation 

possibly advecting as far north as I-90 as we go through the 

afternoon and overnight. Latest HRRR runs support observational 

trends and take much of the heavier precipitation closer to I-80

late tonight. Could still pick up a quick 1/2 to 1 inch of rain

in pockets along and south of Highway 18 before Wednesday 

morning given the ample deep moisture present, but otherwise the

impacts from this rain look to be minimal.



Wednesday Afternoon - Thursday: Dry and Seasonal



Cyclonic flow lingers for the remainder of the week with a 

broad cutoff low centered over the far north-central CONUS and 

south- central Canada. Shortwave ridging passes through from 

Wednesday afternoon through Thursday with the main surface 

baroclinic zone displaced to the south, keeping the risk for any

precipitation at bay. With the flow remaining weak, minimal 

lower tropospheric temperature advection is expected during this

timeframe and highs will only rise into the lower 80s by 

Thursday despite the clearer skies.



Friday - Early Next Week: Seasonal Temps, Periodic Storms



Given the weak flow pattern we find ourselves in with the main 

jet stream shifted north to the U.S./Canadian border, confidence

in the timing and coverage of storms for Friday and the weekend

is low at this time. The deterministic solutions depict the 

possibility of multiple weak perturbations rotating through 

during this period, but the guidance differs on how far north 

the richer Central Plains airmass can advance, which will play 

heavily into the probability of any storms (and surface 

temperatures). Moving into early next week, the jet stream looks

to sag southward and provide more support for organized 

convection. Again, the question of how exactly the thermodynamic

and kinematic spaces line up will play heavily into storm 

strength and coverage. 



&&



.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...

Issued at 1246 PM CDT Tue Aug 4 2026



Periods of showers and perhaps some rumbles of thunder are 

expected this afternoon and overnight which will result in MVFR 

ceilings and visibilities at times. Showers and the associated

impacts will primarily remain south of I-90, though some model 

solutions continue to suggest low probabilities (25-35%) for SHRA

at the TAF sites generally between 00z-06z, so have continued 

with PROB30 groups at both locations. Overnight, low level 

saturation associated with the showers may lead to IFR ceilings 

for areas along/south of Highway 18 as suggested bythe 04.12z 

HREF/REFS which depict 30-50% probabilities for ceiling heights 

less than 1kft. Showers shift eastward Wednesday morning while skies

slowly scatter out west to east throughout the day. Light 

northwest winds continue throughout the TAF period.



&&



.ARX WATCHES/WARNINGS/ADVISORIES...

WI...None.

MN...None.

IA...None.



&&



$$



DISCUSSION...Skow

AVIATION...Falkinham