Area Forecast Discussion

KEY MESSAGES

- Elevated fire weather conditions until this this evening over northern Iowa.

- Warming trend through Wednesday, with mainly dry conditions expected.

- Slight Risk for severe weather across Central Iowa Thursday. Cooler weather to follow.

SHORT TERM /THROUGH WEDNESDAY/

Issued at 235 PM CDT Mon Apr 20 2026

Dry conditions remain overhead today, with mostly sunny skies over Iowa, paired with breezy conditions as south/southeasterly winds gust to 20-30 mph. Efficient mixing has led to drying air at and near the surface, with falling RH values around 25-35%, lowest over northern Iowa where elevated fire weather is a concern, and therefore an SPS has been issued that is in effect until 7pm this evening. Greener fuels over central to southern Iowa however are limiting potential concerns for fire weather today. Temperatures are warming up nicely so far, with values as of this writing in the upper 50s to low 60s, with the expectation for highs topping out in the low to mid 60s northeast and in the upper 60s to low 70s southwest later this afternoon. Surface high pressure currently over the Ohio Valley will continue to lessen its influence further west into the Central Plains as it drifts further eastward this evening into Tuesday, though conditions are expected to remain dry. This evening, 850mb flow increases out of the southwest with the developing low level jet, remaining overhead into Tuesday morning, which will allow for overnight lows to be warmer than what they have the past few days in the mid to upper 40s north and in the low to mid 50s south.

The low level jet slowly fades through Tuesday morning, largely remaining over south/southeast Iowa, where breezy winds are expected with values gusting up to 20-25 mph out of the southwest. On the eastern fringe of the upper level ridge that is currently over the western CONUS, a mid-level shortwave riding this flow is expected to pass over Iowa. With this, a subtle surface boundary is expected to drop south/southeast across Iowa, entering northwest Iowa by mid-morning, and dropping slowly southeastward through the day. While this frontal passage is expected to be largely if not completely dry, a look at CAM guidance shows simulated light showers/few weak storms occurring into the evening over far southern Iowa and further east, though a closer look at soundings at KOTM indicated a near surface layer of dry air despite rather notable forcing for lift in this area. Have kept the forecast dry at this time given these details, though cannot completely rule out some occasional sprinkles in this area.

By midweek, the western thermal ridge continues to build while moving eastward over the Central Plains, leading to continued warm conditions while remaining dry. Returning winds out of the south/southwest and mostly sunny skies are expected Wednesday, with highs expected to reach into the upper 70s to low 80s.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/

Issued at 235 PM CDT Mon Apr 20 2026

As the ridge departs the region into Thursday, a large trough moving over the Pacific Northwest, paired with a deepening surface low over the Dakotas will gradually arrive over the Midwest through the day, bringing active weather back into the forecast. As the warm front remains well into Minnesota, Iowa will be in the warm sector, with temperatures through the 70s and plenty of moisture overhead as dewpoints reach the upper 50s to low 60s. Showers and storms are expected to develop, especially in the afternoon to evening as a cold front slides through the state. There are some notable differences on the speed of this frontal passage, with the GFS having all activity out of Iowa by late Thursday night, whereas the Euro is much slower, keeping showers/storms in the forecast through much of Friday morning before exiting east. Will have to keep an eye on these details over the next few days. In terms of overall setup for storms, a warm and moist airmass overhead, paired with CAPE values up to 1000-1500 J/kg and shear values of 30-35 knots are favorable for strong and even possibly severe storm development, where the SPC continues the 15% severe probabilities over all of Central Iowa for their D4 forecast. More specific details are expected over the coming days. It is never too early though to review plans for action if severe storms are expected to impact your location. Outside of the storm potential, synoptic winds will be very breezy, with southwest winds gusting to 30-40 mph. Given the WAA regime, not expecting later model trends to increase values much to push into possible headline consideration, but will be watching this as well.

Behind the departed cold front into Friday, slightly cooler and mostly dry conditions are expected as highs reach into the 60s. The mid-level feature that was responsible for the activity Thursday is expected to generally remain over the Northern Plains, though the GFS indicates a weak shortwave to its south passing over south/southeast Iowa into Missouri/Illinois indicating additional rain chances, while the Euro is dry. Something to watch through the week given these significant differences.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1055 PM CDT Mon Apr 20 2026

VFR conditions ongoing and expected to continue through much of the TAF period. Main aviation concern remains the LLWS through the overnight hours at all terminals. Scattered cu then expected in at least southern Iowa tomorrow. Some models hint of MVFR, but kept and expecting VFR due to coverage and moisture. Continue to monitor low potential for showers or a few storms near KOTM but confidence in occurrence and impacts remains too low for inclusion.

DMX WATCHES / WARNINGS / ADVISORIES

None.