058
FXUS63 KARX 152322
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
622 PM CDT Wed Jul 15 2026

.KEY MESSAGES...

- Hazardous heat continues this afternoon with the heat index
  rising to near 100. Temperatures will moderate slightly over
  the coming days and triple digit heat index values, present
  this afternoon, will likely be in the rear view mirror outside
  of some river valley locations.

- Smoke from Canadian and northern Minnesota wildfires will
  affect at least part of the area over the next couple days.
  Locations north/east of I-94 will be most affected and could
  see visibility below 1 mile and very unhealthy (level 5 out of
  6) to hazardous (level 6 out of 6) air quality.

- Largely diurnal potential (10-40%) for showers and
  thunderstorms Thursday through Saturday.

&&

.DISCUSSION...
Issued at 155 PM CDT Wed Jul 15 2026

Heat continues, but moderates after this afternoon

Strong upper ridge is present over an axis extending from over Sioux
Falls to the Tidewater region. This, combined with the slight
increase in moisture over the past few days, has led to heat index
values finally reaching the triple digits more than sporadically for
the first time through our ongoing Heat Advisory. Moving ahead to
tomorrow, heights aloft continue to fall with the drop in air
temperatures leading to the heat index remaining below 100. Given
this, the struggle to reach 100 in previous days, and nighttime
temperatures that dropped into the 60s Monday and Tuesday nights,
and potential for smoke to prevent some heating tomorrow - more on
that below - will refrain from extending the Heat Advisory beyond
this evening.

Smoke and hazardous air quality ahead

Areas of wildfires in northern Minnesota and western Ontario have
continued over the past several days. Smoke from these fires has
spread over Lake Superior given northwesterly flow through much of
the column. Winds around 850mb have turned to out of the
north/northeast, bringing some of this smoke into Clark/Taylor
Counties with visibility down to around 1 mile at MDZ. 15.12z HRRR
and 15.15z RAP smoke output suggest this area of smoke will at least
spread to closer to I-94 with the RAP bringing it near to the
Mississippi. Latest indications from MN/WI state air quality
outlooks are that level 5 (very unhealthy) to 6 (hazardous)
conditions will be present where smoke is thickest, mainly along and
north/east of I-94. 15.15z RAP suggests near surface smoke will
begin to improve Thursday afternoon into Friday as southerly flow
near the surface ramps up due to a lee surface trough developing in
the central High Plains.

Thunderstorm potential returns

Return of northwesterly flow aloft will also bring chances (10-40%)
for thunderstorms Thursday through Saturday during the
afternoon/evening hours. Each day should (70-90% for 1000 J/kg per
15.00z LREF) have sufficient instability for strong thunderstorms
but shear needed for convective organization appears to be lacking,
save for Saturday - but then the upper disturbance needed for
thunderstorms to initiate may eject southeast several hours before
peak heating. In summary, those with outdoor plans will need to
remain alert for potential lightning starting Thursday, but severe
storm concerns remain very low at this time.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 622 PM CDT Wed Jul 15 2026

Both smoke and fog are the main concerns through Thursday. Dense
Canadian wild fire smoke will gradually work south into the
Interstate 90 corridor overnight. This smoke will then persist
through the day along and north of Interstate 94.

With light winds up to 10K feet tonight, we will likely see
valley fog develop. Dense fog is expected at KLSE from 06.10z
through 06.14z.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Heat Advisory until 8 PM CDT this evening for WIZ029-032>034-
     041>044-053>055-061.
MN...Heat Advisory until 8 PM CDT this evening for MNZ079-086>088-
     094>096.
IA...Heat Advisory until 8 PM CDT this evening for IAZ010-011-030.

&&

$$

DISCUSSION...Ferguson
AVIATION...Boyne