textproduct: Des Moines

KEY MESSAGES

- Warm temperatures continue to start this week with highs in the mid 80s to near 90 today and Wednesday. Brief cooldown mid-week with highs still in the low 80s through end of week.

- Scattered shower and non-severe thunderstorms persist this morning. Additional shower and storm chances (20 to 30%) are expected late this afternoon into the evening and again late Wednesday into early Thursday, both over northern Iowa. The severe risk is low, but gusty winds and hail are possible.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 302 AM CDT Tue May 26 2026

Rain and thunderstorms continue over north central Iowa early this morning, as a 30 kt low level jet noses up into the northwestern corner of the state. The instability available to storms isn't overly high (~1000 J/kg) but has been enough for a few more ambitious updrafts. However, the lack of any notable wind shear has ultimately led to a quick demise of any of these stronger updrafts, resulting in pulsey convection. Hail will be the primary threat with these up then down storms through the morning, as well as gusty winds around 30 to 40 mph as the stronger updrafts collapse on themselves. The low level jet will likely keep scattered showers and storms ongoing over north central Iowa through the morning hours, with activity diminishing as the jet weakens after sunrise. The potential for stronger updrafts (and associated impacts) will also be waning through the morning as the available instability slowly diminishes through the nighttime hours.

The conditions today and Wednesday generally remain status quo from what we've seen over central Iowa the last few days, albeit with more widespread temperatures in the upper 80s and not as breezy of winds. As was pointed out in yesterday's discussion, the 500 mb pattern lacks any prominent features over Iowa through mid-week. At 500 mb, the midwest will be sandwiched between a broad cutoff low developing off the west coast and persistent troughing to the northeast, putting Iowa beneath a weak ridge. Through today and Wednesday, this will keep the thermal ridge overhead and temperatures warm. The stronger low- to mid- level jet from the last few days will orient more over the plains ahead of the west coast low, keeping that gulf moisture stream displaced to our west. The rest of the moisture will be shunted south and east of Iowa by the building trough to our northeast. That said, while new moisture won't be advecting in, residual moisture from the last few days will remain pooled over Minnesota and northern Iowa. This residual moisture will coincide with destabilizing environments both today and Wednesday, leading to diurnally driven showers and thunderstorms both days.

For today, convective initiation is expected over southern Minnesota late this afternoon with an outflow boundary oozing southward and kicking off additional rain/storms over northern Iowa through the evening. The 0-6 km wind shear available to storms this evening will be extremely low (less than 20 kts) but the ~1500 J/kg of MUCAPE will be sufficient for at least a few stronger updrafts. Like this morning, without any wind shear, these stronger updrafts will quickly collapse in on themselves, leading to pulsey convection. Because of this, the severe threat will be low, although small hail and/or gusty outflow winds may occur with collapsing updrafts. The storm prediction center does have a marginal risk for severe weather (level 1 of 5) just scraping our north, focused mainly where convective initiation is expected in southern Minnesota.

This pocket of residual moisture generally remains through Wednesday, albeit less robust compared to tonight. The moisture pool will begin to push back southwestward into Iowa as high pressure begins to build over the Great Lakes. As this occurs, scattered showers and storms are once again forecast to develop over Minnesota into northern Iowa late Wednesday afternoon into the evening. Much like this morning and tonight, daytime destabilization will boost instability values but shear will be minimal. Therefore, expect similar storm characteristics to the previous two rounds of scattered convection; pulsey storms producing gusty winds and small hail, but with a low risk for long-lived severe storms.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 226 PM CDT Mon May 25 2026

The upper air pattern is more pronounced to the west with a level large cut-off upper level low that will be nearly stationary and churn across the west coast most of the week. The west edge of the flow around this trough will align well with the gulf and pump moisture through the central plains. By late week this unstable axis of moisture will shift ever so slightly to the east, beginning to skim parts of southern and western Iowa on Thursday. This may allow for a window of thunderstorm activity into southern and western Iowa from Thursday into the weekend. There is still no robust forcing mechanism so at this time severe storms are unlikely. The main uncertainty is how far this plume of instability will make it and how much of Iowa will (or will not) be impacted.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 630 AM CDT Tue May 26 2026

Showers and occasional thunder linger over northern Iowa this morning, primarily impacting KMCW. Current trajectory would suggest this activity could reach KALO later this morning, but expectation is for showers/storms to dissipate through the next few hours, so have kept shower mention out of TAF for now.

Rain and clouds diminish north today, giving way to VFR conditions and light southerly winds at all sites today. A few showers/storms may develop over northern Iowa again tonight, mainly near KMCW and KALO, but have kept PROB30 for SHRA and no thunder mention due to uncertainty in exact timing and impacts.

DMX WATCHES/WARNINGS/ADVISORIES

None.