textproduct: La Crosse

KEY MESSAGES

- Hot and humid conditions arrive Monday and continue through much of next week with heat indices generally in the 95 to 105 degree range, with Monday and Tuesday being the hottest as high temperatures will be in the mid to upper 90s and heat indices in the 100 to 110F range.

- Periodic shower and storm chances are possible each day this week.

DISCUSSION

Issued at 213 PM CDT Sun Jun 28 2026

Today: Storm Chances?

An MCS moved through the area this morning and early afternoon producing widespread rainfall. The better rain amounts were in portions of northeast Iowa. As a result of this MCS, the anvil continue to remain over the forecast area. Over the past hour or so this anvil has slowly shifted eastward, leaving our western tier of counties outside of the anvil influence. Outside of our forecast area in northwest and west central Iowa, billow clouds (indicating a stable environment) have morphed into a cumulus field (indicating a potentially more unstable environment). Over the past hour, this transformation has continued to move into central Iowa as the anvil shifts off to the east. This warm front will shift northward throughout the rest of the day. The question for today is if the ridge that is going to be amplifying throughout the day will keep the area capped off from storm development, or if the warm front will be enough for storm initiation. Current NBM hourly PoPs have a 15 to 30% chance for storms this afternoon and early evening to highlight this potential, before increasing later this evening as moisture transport increases. If a strong enough storm can occur then damaging winds or large hail would be the most likely hazard type. Most CAMs are highlighting this evenings convection which is focused north of I-94 for the evening before eventually pushing north of the forecast area after midnight. In addition, due to the anvil overhead temperatures will likely be a little cooler than what is currently forecasted.

Monday-Friday: Hot and Humid Conditions, Periodic Storm Chances

Ensemble and deterministic guidance continues to show the ridge amplifying off to our east and then staying over the eastern CONUS through the week. This leaves our area in southwest flow, which will push hot and humid air into the Upper Midwest through the rest of the week. The 850mb temperatures for Monday will be the warmest of the week with temperatures in the 23 to 26C range, which will translate to high temperatures in the mid to upper 90s. Dewpoints will be in the mid 70s through the week, which for tomorrow means that heat indices will be in the 100 to 110F range. An Extreme Heat Warning is in place for Monday through Tuesday for these heat indices. Tuesdays heat indices are a little lower than Monday but still in the 100 to 105F range. There will also be poor overnight recovery as temperatures remain in the mid to upper 70s, which is the reasoning for the continuation of the Extreme Heat Warning from Monday through Tuesday. Southwest flow continues for the latter portions of the week which will help high temperatures stay in the low to mid 90s and heat indices stay in the mid 90s to low 100s.

Each day this week there is a wave moving through the Upper Midwest which could help initiate storms. With the amount of instability available each day coupled with each wave, there is some severe storm potential every day. CSU ML probabilities have our area in a 15% chance for severe weather every day until Sunday. The main uncertainty is how capped the environment will be each day. The first storm chance is Monday evening as a cold front moves southeastward across the CWA. At the same time a low-level jet increases (40 to 50 kts) which could help initiate storms. One thing these storms could do is lower the heat risk for the any given day as cloud cover from the storms could lower the temperatures enough to be outside of any heat headline being issued.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 619 PM CDT Sun Jun 28 2026

MVFR cigs will likely persist across much of the region through the evening and into the overnight as low-level moisture remains locked in place due to a warm frontal passage. As this front passes through the area this evening, showers and some storms will be likely near and north of I-90 which may reduce visibilities to MVFR and possibly IFR levels underneath any storms. A couple of storms may be strong with small hail and gusty winds, especially north of I-94. MVFR cigs will begin to disperse during the daytime hours on Monday as diurnal mixing begins with winds increasing to 15-20 kts by afternoon with gusts up to 30 kts from the south.

ARX WATCHES/WARNINGS/ADVISORIES

WI...Extreme Heat Watch from Monday afternoon through Tuesday evening for WIZ032>034-041-042-053>055-061. MN...Extreme Heat Watch from Monday afternoon through Tuesday evening for MNZ079-086>088-094>096. IA...Extreme Heat Watch from Monday afternoon through Tuesday evening for IAZ008>011-018-019-029-030.