textproduct: Des Moines

KEY MESSAGES

- 30-60% chance for showers and thunderstorms mainly in northern and eastern Iowa, beginning around midday. The threat of severe weather or widespread rainfall is low.

- More substantial (70-100%) and widespread rain and thunderstorm chances are forecast Saturday night and Sunday. There may be some risk of severe weather mainly in southern Iowa. There is also potential for heavy rain and localized flooding, mainly in the southern half of Iowa.

SHORT TERM /THROUGH SATURDAY/

Issued at 304 AM CDT Fri Jun 19 2026

High pressure is gradually leaking south this morning and has led to mostly clear skies and light and variable winds. Lows this morning will be in the 50s, even some 40s in the far north. The 850mb reflection of the surface high will pass over southern Iowa today with some of the moisture leaking in from the southwest. 60 dew points will collect in the southeast half of the state, but the PBL will be well-mixed. Aloft will be a shortwave riding the northwest flow, ejecting across Minnesota. 500mb flow will exceed 50kts by this afternoon. Have increased coverage of precipitation in northern and central Iowa today as synoptic lift will dominate rather than frontal, resulting in broad showers in northern Iowa. That said, the leading edge of the showers will feature thunderstorms firing off a thermal gradient, affecting mainly the eastern half of the state. The main concern with thunderstorms will be the wind potential, given the inverted-V soundings. The mixed-layer winds peak between 20 and 30kts, and evaporative cooling processes with thunderstorm cold pools could result in gusts to around 40mph. As for hail: the shear profile is favorable for hail production, but the lack of moisture makes the potential for this sub- marginal. There is a Marginal Risk for severe weather just outside the DMX CWA where convective coverage is comparatively more abundant near the parent shortwave. Highest confidence for the gusts and hail will be in the northeast quadrant of the state, but the risk for severe weather is low (<10%).

Southeast winds dominate Saturday and clouds will increase through the afternoon beginning in the southwest. Highs will be similar to Friday, within a few degrees of 80. Additional showers and storms build in later Saturday night, which is covered in the long term section below.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/

Issued at 212 PM CDT Thu Jun 18 2026

By Saturday afternoon, a 500 MB trough will be moving over the Rockies and approaching the High Plains. The vorticity embedded within this trough will be split into at least two distinct shortwaves, the first of which will move across Nebraska and northern Kansas Saturday night, and Iowa on Sunday. As this system approaches on Saturday, broad surface low pressure will develop over the southern High Plains, while a surface high pressure ridge over the Upper Midwest steadily retreats northeastward away from Iowa. By midnight Saturday night, the surface trough will coalesce into a trough somewhere around southwestern kansas, with an effective warm front extending east northeastward along or near the Iowa/Missouri border. Deep and persistent moisture transport ahead of the system will result in significantly increasing PWAT values across the region, such that by 12Z Sunday PWATs will approach 2" in far southern/southwestern Iowa, which is well above normal for the season. While there is some disagreement among various deterministic models in the details of convective evolution, it does appear likely that some type of thunderstorm complex will form over southern Nebraska or far northern Kansas Saturday evening, then spread eastward or east southeastward along the frontal boundary. This complex may affect our southern counties Saturday night, or may remain farther south across Kansas and Missouri. Meanwhile, north of the boundary widespread rain will develop across most or all of Iowa, as broad forcing for ascent ahead of the approaching shortwave meets deep available moisture and modest elevated instability in place across Iowa. By late Saturday night and into Sunday the current forecast calls for PoPs of around 60% in our north to near 100% in the south.

While rain is likely to a near certainty from late Saturday night into Sunday, the associated threats are somewhat less clear. Given the time of day, saturated atmospheric column, and limited instability north of the aforementioned warm front, the severe weather threat should be generally low across Iowa. An exception to this is in far southern Iowa, where depending on the location of the front and track of the associated thunderstorm complex discussed above, there may be a threat of strong winds if the forecast trends northward and sufficient near-surface instability is introduced. Aside from severe weather potential, the more growing concern at this time is the possibility of heavy rainfall and localized flooding. Deterministic guidance paints generally 1.5-3" or so of QPF across the southern half of Iowa from midnight Saturday night through the day Sunday. However, much of the deterministic guidance is at the higher end of the ensemble envelopes. For example, the deterministic NBM depicts 2.2" of QPF at Des Moines and a maximum of 3.0" in Taylor County, however, it also indicates only a 20% chance of exceeding 3.5" at Des Moines and a 35% chance along the Iowa/Missouri border. This indicates that while substantial rainfall is likely, very high or extreme amounts are less likely than might otherwise be expected. In addition, for most solutions within this general scenario, the rain should be of a longer-duration, which those amounts (if they even occur) falling over the course of 18 hours or so, rather than in a short burst, which lowers the flash flooding threat. The season also raises the bar for rainfall intensity/amount needed to get a response, due to the peak state of most crops and vegetation at providing capacity. Finally, in terms of river flooding, if the heaviest rain does fall from southwestern into southern Iowa, it will be near the state divide an in smaller basins that quickly drain out of the area, somewhat limiting the river flooding threat. All that being said, these concerns will be closely monitored over the next couple of days, as the forecast could easily shift more toward a more northern and/or heavier rain solution, or toward a more southern and/or less heavy rain solution. If the more northern/heavier rain solution verifies, then we could see heightened flooding/flash flooding concerns in some parts of our southern and even into central areas.

The weekend rain/storm system will gradually push off to the east later Sunday, after which forecast confidence decreases rapidly. This is primarily due to the evolution of the second shortwave within the larger 500 MB trough as mentioned earlier, which long-range models are not handling well in terms of consistency between models or from run to run. The result is persistent low to moderate (10-50%) PoPs in the first half of next week, with a continuation of near to a little below normal temperatures. Looking into the way-out machine, it does appear a large 500 MB high pressure area will become established over the southwestern U.S. by the latter half of next week, with a ridge extending up along the Rockies. If this ridge remains shunted somewhat southward and Iowa lies beneath broad cyclonic flow to its northeast, then seasonal temperatures and intermittent rain chances would be likely to continue. On the other hand, if the ridge exerts its influence farther northward, and the cyclonic storm track is pushed northeast of Iowa, then it could favor gradual warming and a somewhat drier forecast. We will see how this plays out as we have several more pressing systems to get through before then.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1242 PM CDT Fri Jun 19 2026

Scattered to numerous showers and isolated thunderstorms will develop this afternoon into this evening. Due to modest moisture, still expecting generally VFR CIGs except near any heavier showers where brief MVFR conditions are possible. Same goes for VSBY, VFR except during any heavy shower or tstm. Gusty winds are possible near any precipitation cores, due to the higher cloud bases and dry subcloud layer. Any precipitation will gradually end from north to south this evening. Prevailing winds will generally favor a westerly direction.

DMX WATCHES/WARNINGS/ADVISORIES

None.