textproduct: Des Moines

KEY MESSAGES

- Limited storm coverage in Iowa today due to a strong cap, except a conditional Slight Risk (Level 2 of 5) over northern Iowa if storms can initiate or move in from the north.

- Higher confidence of severe storms and locally heavy rainfall on Tuesday. Portions of central/eastern Iowa upgraded to a Enhanced Risk (Level 3 of 5) with all severe hazards possible.

- Additional periods of severe storms and locally heavy rainfall on Wednesday and again on Friday followed by a cooler weekend.

- Warm and breezy today through Friday with highs in the 70s and 80s.

SHORT TERM /THROUGH TUESDAY/

Issued at 232 AM CDT Mon Apr 13 2026

Main point, an active and challenging forecast through Friday! We'll try to break down the key points:

Today and tonight...Primary Severe Risk is northern Iowa...

A southwesterly upper flow pattern will continue across the upper Midwest with an attendant sfc low developing in the SD/NE/IA tri-state area. Moderate to strong WAA in the 850-700mb layer today will advect a seasonally strong EML across IA through afternoon. Several models try to develop isolated elevated showers/t-storms as the deeper moisture/theta-E returns, which is possible in these WAA regimes. Model consensus then shows Iowa in the "capped" warm sector through early evening, with model soundings indicating the possibility of low level stratus and robust values of MLCIN. The one important change from yesterday is that position of the sfc low and associated warm frontal feature has been nudged southward a bit, with the warm front now extending eastward generally along the MN/IA state line. As noted, due to the magnitude of the CIN, and overall weak background forcing, feel that convective initiation will be difficult to achieve over IA, which is supported by a vast majority of the deterministic and CAM solutions, and the SPC Day 1 Outlook. It should be noted that a few CAM solutions do try to initiate storms across far NW IA or SRN MN, near the triple point of the sfc low, which would then track across far northern IA. If a storm "could" get going, the CAPE/shear parameter space would be favorable for supercells, including very large hail, severe winds, and a possible tornado. At this point, confidence for severe storms in IA is low (<20%). A more likely scenario is late afternoon/evening CI occurring north in SD/MN, with additional convective coverage in the evening and overnight as the nocturnal LLJ strengthens. A few of these storms or convective cluster, could try to advect swd into the instability axis, and scrape the far northern IA counties. Bottom line, key features to watch today are 1) warm front position; 2) stratus development; 3) magnitude of MLCIN.

It will be breezy and warm today, with highs in the upper 70s to lower 80s, assuming breaks in the stratus. Again, not expecting a ton of activity tonight, except perhaps across far northern IA as mentioned above.

Tuesday...Highest Severe Risk across central and eastern Iowa...

As noted in previous discussions, the convective evolution today/tonight often plays a major role what happens in subsequent days, so details for Tuesday may need to be adjusted.

With this in mind, the synoptic pattern is not expected to change much Tuesday. However, a slightly stronger upper shortwave is progged to move across the Midwest on Tuesday afternoon providing more support for lift. In addition the sfc low is expected to reorient and sag southward into western Kansas with the sfc boundary extending newd from NW MO, across central IA, and into the Great Lakes region. Strong destabilization by late afternoon, and frontal convergence should initiate at least scattered storms along the front by evening, aided by the LLJ. The highest potential for storms attm is across east-central Iowa, where the SPC has introduced the Enhanced Risk (Level 3 of 5). Strong instability, steep lapse rates, and very strong winds aloft /0-6km shear of 50-60kts/ would support supercell development and all convective hazards, in particular very large hail per sounding analogs. With high PWATs, locally heavy rainfall is also possible, especially with any training storms. Tuesday is defintely a day to watch closely.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Issued at 243 PM CDT Sun Apr 12 2026

Wednesday...Highest severe risk in the eastern half of Iowa. Many details remain in question for Wednesday due to proceeding days convection. However, latest deterministic and ensemble guidance suggests Wednesday may have a more dynamic shortwave and deeper sfc low (perhaps sub 1000mb), and the triple point over IA. High convective impact ceiling if things evolve badly.

Thursday...looking like a "lull" day as the synoptic pattern reorganizes.

Friday...Perhaps the strongest upper shortwave and closed low, attendant sfc low, and strong cold front. Many details yet to be determined.

Next Weekend...much cooler behind a strong cold front, possible showers.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1059 PM CDT Sun Apr 12 2026

Have trended more to stratus instead of fog in the short term. Stratus is building in central to northeastern Iowa and will create MVFR and later IFR cigs after 10z, lifting slowly through the morning. Thunderstorm trends have been more south this issuance, so added Prob30 mentions for northern terminals. Still uncertainty in storms further south, but they would occur within the last three hours of the period. LLWS present at KOTM tonight and will cover all sites after 00z.

DMX WATCHES/WARNINGS/ADVISORIES

None.