121
FXUS63 KARX 302331
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
631 PM CDT Sat Aug 30 2025

.KEY MESSAGES...

- Mostly dry conditions this weekend with an isolated shower or
  storm possible for portions of southeast Minnesota and
  northeast Iowa, with the better chances remaining west of
  I-35.

- The chances for widespread rain continue to increase (50 to
  70%) for Tuesday into Wednesday as a cold front moves through
  the region.

- Near-normal temperatures through Tuesday then below normal
  temperatures through the end of the week.

&&

.DISCUSSION...
Issued at 131 PM CDT Sat Aug 30 2025

Today-Monday: Mostly Dry and Seasonable Temperatures

The surface boundary that has been over the region the past couple
of days has shifted into central Iowa. There is still a little
uncertainty with how far south it goes, so a shower or storm can not
be ruled out for portions of northeast Iowa this afternoon and
Sunday afternoon. By Monday, the boundary shifts back a little
northeastward and thus increases PoPs a little (10 to 20%) for
portions of northeast Iowa and southeast Minnesota with the better
chances staying west of I-35. With surface high pressure over the
area through Sunday, fog will be possible especially in low lying
areas and river valleys. Seasonable temperatures in the mid to upper
70s are expected into early next week.

Tuesday-The Weekend: Trending Cooler with Rain Chances Midweek

Heading into Tuesday, a strong trough and associated cold front digs
down into the Upper Midwest and Great Lakes Regions. With the
current timing, the cold front arrives late Tuesday into early
Wednesday morning. This will bring increased chances of showers and
storms (50 to 70%) for Tuesday evening through Wednesday morning.
PWATs are around the 0.8 to 1.25 inch range so the rain totals will
be relatively light, as is depicted in the 00Z LREF where there is a
30 to 60% chance for at least 0.25 inches to fall, with the higher
probabilities in central Wisconsin. With cyclonic flow in place as
the trough gradually shifts eastward, rain showers may be possible
both Thursday and Friday.

The bigger impact from this deep trough moving into our region will
be the cooler temperatures. The 850mb temperatures for Thursday
range from 1C to -3C. There are some differences in the ensemble and
deterministic guidance as the GFS and GEFS seems to be a bit cooler
than the ECMWF and EPS, however the confidence for temperatures to
be quite a bit below normal are high. EFI values for Thursday
continue to range from -0.8 to -0.9 which indicate the high and low
temperatures for Thursday are on the lower end of climatological
normal. Current NBM populates Thursday morning with lows in the mid
30s in Central Wisconsin to the low 40s for everywhere else in our
CWA. High temperatures for Thursday are now forecasted to be in the
mid to upper 50s. Now these temperatures will continue to fluctuate
a bit as we are still 5 days away from this taking place. After
Thursday, temperatures gradually warmup as the trough shifts
eastward and by Saturday we are looking at temperatures back near
70F.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 624 PM CDT Sat Aug 30 2025

Aviation concerns continue to focus on a likely valley fog - and
potentially outside of valley fog as well - event tonight into
early Sunday morning. Confidence in fog within valleys has
increased so have gone with LIFR fog and ceilings at LSE from
09z to 14z and included this throughout valleys and the
BCK/VOK/82C/CMY area as well. At RST and in areas west of the
Mississippi Valley confidence is lower, so have stuck with a
few hours of MVFR. This time of year, fog/stratus will tend to
dissipate around 14z so have gone with that ending time with
this update. That said, may need to adjust this time farther
into the morning should trends continue to strongly point toward
valley fog.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.

&&

$$

DISCUSSION...Cecava
AVIATION...Ferguson