Area Forecast Discussion

KEY MESSAGES

- Cooler temperatures will be in place through the work week before another warmup this weekend.

- Meaningful chances for rain return Thursday night into Friday morning in southern Iowa where rainfall totals over half an inch are possible.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 210 PM CDT Tue Jul 21 2026

Relief from the heat finally sets in today as cold air advection in the wake of yesterdays cold front brings in temperatures in the 70s and 80s. Diurnal heating has caused a wide area of cumulus to form across northern to central Iowa, but aside from that skies are overall clear and conditions dry. Some smoke is still hanging around, mainly aloft, but not seeing any visibility reductions across the state so did not include it in todays forecast. Efficient mixing down of stronger mid level wind is already well underway, and wind gusts of 20-30 mph will likely continue through the end of the afternoon today.

By Wednesday, high pressure becomes well established across Iowa. However, a subtle shortwave is expected to move through the enhanced mid level flow on the periphery of the 500mb ridge sitting on the southern and central plains. As this shortwave approaches in the afternoon, the 500-700mb layer will become saturated and form a few showers over southwest Iowa. That said, this rain will have to fall through the the dry Canadian airmass that is being advected in today, and most of it will likely evaporate before reaching the surface. Still, included isolated to scattered PoPs but minimal QPF for southwest Iowa through the afternoon. Highs will also be even lower on Wednesday due in part to the continued cold air advection through the morning and increased cloud cover during the daytime heating.

LONG TERM /THURSDAY THROUGH TUESDAY/

Issued at 210 PM CDT Tue Jul 21 2026

A stronger wave looks to move across the top of the ridge by Thursday evening and bring us our next chance for meaningful precip. Instability will be quite limited so severe weather is unlikely, though some thunder is possible Thursday night into Friday morning in southern Iowa. The nocturnal LLJ returns to our vicinity during the Thursday overnight, with the nose centered over southwest Iowa. This should erode the dry air and allow the quite saturated mid levels to rain down to the surface. The main story will be QPF amounts. WPC has southwest Iowa in a marginal ERO for Thursday and Friday, and PWATs are well over 2 inches. There is a large QPF spread across the models, but a few give spots in southern Iowa 1-2 inches of rain. By the weekend, the ridge intensifies over the Dakotas, bringing us another period of heat. We may breach the 90s again on Saturday, and Sunday/Monday look to be the warmest as a more substantial EML is advected in.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 628 PM CDT Tue Jul 21 2026

VFR conditions to prevail through the end of this TAF period. Winds will remain gusty until around sunset, but will subside as daytime heating wanes. Clouds will also begin to clear out, yielding mostly clear skies overnight. There is a slight chance of haze tomorrow morning in SW Iowa, but it will not impact terminal sites. However, as daytime heating resumes, cumulus clouds could return to Central Iowa tomorrow afternoon.

DMX WATCHES / WARNINGS / ADVISORIES

None.