textproduct: Des Moines

KEY MESSAGES

- Scattered severe storms (Level 3 of 5) this afternoon and evening. All severe weather hazards remain possible. More widespread storms and locally heavy rainfall expected tonight, especially over the southern half of Iowa, but with a lower severe weather threat overall.

- Additional rounds of severe storms and locally heavy rainfall still expected on Wednesday afternoon and evening, and again on Friday afternoon and evening. Details on those events will be fine tuned in subsequent updates.

- Warm and breezy today through Friday with highs in the 70s and 80s. Much cooler readings in the 40s and 50s by this weekend, with a hard freeze likely north Saturday night.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 140 PM CDT Tue Apr 14 2026

A broad 500 MB trough is moving over the U.S. Rockies today, and is not well coalesced with several vorticity maxima strung out along its loose axis. Ahead of the trough, Iowa remains beneath southwesterly steering flow resulting in, relative to the season, warm and quite humid conditions across the state. A surface low pressure center is slowly developing ahead of the 500 MB trough, near the Colorado/Kansas border, with a nearly stationary front extending northeastward over roughly the northern half of Iowa. Satellite imagery shows agitated cumulus clouds developing along and near the frontal zone, and forecast soundings indicate a weakening EML in place that could break at any time. All CAMs initiate convection and form scattered thunderstorms within the next couple hours, most likely near the front roughly north of I-80. Instability is seasonally strong with SBCAPE in excess of 3000 J/KG south of the boundary, and impressive bulk shear values of 40-60 KT are overspreading the area. Wind profiles do show somewhat unidirectional flow in most of the column so this is nearly all speed shear, which mitigates the tornado threat somewhat. Nevertheless, surface-based convection is likely to initiate very soon and continue into the evening. Tornadoes will be possible in any localized backed flow or storms with deviant motion, most likely near the frontal boundary. In addition, any storms will be capable of large hail given the relatively cool mid-levels, strong speed shear, and impressive instability, and the stronger winds aloft will be easy to transport down to the surface with any cold pools. Thus, all modes of severe weather will be possible with the storms this afternoon and early evening.

Later this evening and tonight, a subtle shortwave impulse will eject out of the broader approaching trough and move across northern Missouri and Iowa, in conjunction with a developing nocturnal low- level jet. This will provide the impetus for renewed convection tonight, with scattered to numerous showers and thunderstorms especially over the southern two thirds or so of Iowa. Several high- res model solutions indicate that the surface frontal boundary will be lingering in our southeastern counties this evening, roughly south of a Creston to Grinnell line, with instability pooling along it and modest convergence providing extra focus for initiation. As a result, these solutions depict stronger thunderstorms developing in that area, with forecast soundings indicating strong instability and deep- layer shear supportive of large hail and damaging wind gusts. This threat should be confined to areas near and south of the boundary, with instability waning rapidly to the north toward central Iowa.

On Wednesday the broad trough over the Rockies will kick out eastward into the Midwest, with the associated surface low gradually tightening up and moving northeastward to near the Nebraska/Iowa border by the evening. Within the warm sector ahead of and wrapping into the surface low, instability will likely increase significantly during the day. However, there is considerable uncertainty in convective timing and evolution due to the after-effects of overnight storms tonight. In fact, many 12Z model runs from this morning depict additional redevelopment of elevated storms mid-to-late Wednesday morning, which would carry some threat of large hail per forecast soundings and further complicate the forecast for the afternoon and evening. Even so, the degree of destabilization during the afternoon should support more rigorous development later in the day, and once again strong instability and deep-layer shear may be very supportive of a severe weather threat. This will be particularly true as the surface low and triple point approach from the west late Wednesday afternoon/early evening, with backing flow and boundaries tied into the low supporting some enhancement of the tornado threat. These storms will surge eastward out of our forecast area by late evening, though a few weaker storms may develop later, in association with the main 500 MB trough moving through, around Wednesday night.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 1239 PM CDT Tue Apr 14 2026

On Thursday a weak ridge will move through Iowa, providing a most welcome respite in the form of a dry, mostly sunny, and mild day with highs roughly in the 75-80 degree range and modest breezes. By Thursday night however, an even deeper longitudinal 500 MB trough will be moving into the Rockies, heralding more active weather to end the week. A surface cyclone will develop in the Southern High Plains with a long inverted trough and sharp baroclinic zone extending northeastward across the Midwest. By Friday morning this front will span from central Kansas, across northwestern Iowa, and into western Wisconsin. Destabilization will occur ahead of the front during the day Friday, and by the afternoon CAPE of 1500-2500 J/KG is likely in at least parts of our area, mainly the southern half. Deep-layer shear will be fairly modest and mostly in the form of speed shear, however the strong dynamic forcing ahead of the approaching trough, convergence along the front, and increasing instability will combine with this shear to be more than sufficient to support severe weather potential Friday afternoon and evening, as outlined by SPC outlooks.

The storm system will push quickly through Friday night and clear us out, though there may be some light wraparound precipitation in our northern counties lingering into Saturday as the final lobe of the 500 MB trough moves by. With much colder air surging in behind the late Friday front and temperatures expected to fall into the 30s across much of our area by early Saturday, a few flakes of snow cannot be ruled out in northern Iowa but no real accumulation or impact would be expected. Highs on Saturday will be nearly 30 degrees cooler than on Friday, ranging in the mid-40s to mid-50s, then falling even further Saturday night into Sunday morning with lows in the upper 20s to mid-30s across Iowa resulting in a frost/freeze in many areas. The good news is this cooler weather will be short- lived, as a ridging pattern sets up in the first half of next week supporting a gradual warming trend.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1236 PM CDT Tue Apr 14 2026

Cumulus clouds are developing across much of the area this afternoon and will produce periods of MVFR ceilings in the next few hours, mainly at FOD/MCW/ALO, before rising to VFR. In addition, scattered thunderstorms are forecast this afternoon and evening, then later tonight into Wednesday morning. Confidence in timing and placement is low, but warrants PROB30 groups during the most likely time windows at each terminal. Lowered ceilings and visibilities and gusty winds will be possible in and near any storms. Expect amendments and refinements to the TAFs later today through tonight.

HYDROLOGY

Issued at 119 PM CDT Tue Apr 14 2026

Multiple rounds of seasonally moderate to heavy rain this week will lead to renewed flooding concerns. Concerns will include possible renewed or additional river flooding as well as flash flooding.

Output from the GFS- and NBM-forced medium-range National Water Model (NWM) and the Hydrologic Ensemble Forecast System (HEFS) suggest the most likely scenario will be moderate to significant within-bank rises on many rivers and streams across the CWA over the next week, especially across the southeast half. Some locations may see minor river flooding as well. These rises will be due to the additive effect of multiple rounds of rainfall. If rainfall is higher than presently forecast then the risk of several locations seeing minor flooding and a few locations seeing moderate flooding will increase.

Flash flooding is less of a concern than river flooding, however the risk is nonzero. The additive effect of rain events will result in a slightly higher risk of flash flooding from Friday into Saturday. The most likely scenario through the end of this week will be ponding of water or low-end flash flooding especially in urban areas or areas that receive repeated heavy rainfall over a relatively short time period.

DMX WATCHES/WARNINGS/ADVISORIES

None.