textproduct: Des Moines

KEY MESSAGES

- Scattered light showers and a few thunderstorms across the northern half of Iowa this afternoon and evening. Severe weather is unlikely in that area. Another round of scattered storms over far southern and southeastern Iowa after sunset tonight, where there is a Marginal Risk of large hail and strong wind gusts with any storms.

- Strong southerly breezes today, with speeds of 15-25 MPH in most areas this afternoon and gusts to near 40 MPH in our northwestern counties. Combined with continuing dry conditions as relative humidity falls below 30% this afternoon, there are elevated fire weather concerns in parts of northern and western Iowa.

- Warmer and more active at times from later Friday into early next week. Highs generally in the 80s each day and may touch 90 in some places. Several rounds of thunderstorms from late Friday through Monday.

SHORT TERM /THROUGH FRIDAY/

Issued at 137 AM CDT Thu May 14 2026

It has once again been a dry, quiet, clear, and seasonally cool night across the region with temperatures falling into the upper 40s to mid-50s as of this writing. However, changes are on the way in the form of warmer and stormier weather over the next several days. A large surface high pressure area is currently retreating eastward from Wisconsin and Illinois toward the Great Lakes region, with surface flow in our service area turning around to light southeast and cool, dry air flowing in from the departing high. Meanwhile, at 500 MB a thermal ridge is moving over the High Plains and will cross Iowa during the day today. Hot on its heels, a 500 MB low is moving from Montana up into far southern Canada, where it will translate slowly east northeastward over the next couple of days. This will place Iowa beneath relatively brisk zonal to slightly cyclonic steering flow for the remainder of the week.

A 500 MB shortwave impulse will round the base of the low moving up into southern Canada today, emerging over the Upper Midwest this afternoon and evening. In advance of this impulse, a broad surface low pressure trough will develop along the lee of the Rockies today. The pressure gradient between this trough and the departing ridge over the Great Lakes will tighten up over Iowa today, especially in our western counties this afternoon. Surface winds will turn to south southeast and accelerate in response, resulting in another breezy day across Iowa. The south southeasterly fetch along with aforementioned thermal ridging aloft will generally support warmer weather today. However, the broad forcing for ascent associated with the shortwave aloft will result in increasing clouds from west to east during the day, which will blunt the warming a bit. Even so, highs are forecast in the upper 70s to perhaps 80 across our area this afternoon. Meanwhile, the current forecast calls for sustained winds of 20-25 MPH across much of the area by the afternoon, with gusts to near 40 MPH especially in our northwestern counties. Combined with RH falling into the 25-30% range this will support elevated fire weather concerns across northern and western Iowa, though mitigated by the greenness of many surface fuels.

Aside from temperature and wind effects, PoPs also return to the forecast today as the shortwave approaches. The aforementioned broad lift supports a possibility of showers and thunderstorms this afternoon and evening across about the northern half of Iowa, and most model solutions depict light echoes/QPF accordingly. Forecast soundings to illustrate a relatively stout surface dry layer that will need to be overcome, however, at least scattered light showers and a few thunderstorms should still occur in our northern counties where 40% PoPs are carried. It remains to be seen how far south these will be able to spread toward central Iowa, as most of the forcing is focused to our north, and the surface dry layer is a bit deeper/stronger the farther south one goes. In any event, limited instability and shear are not supportive of severe weather during this time. The same is unfortunately not true in southern Iowa tonight, where additional showers and thunderstorms may develop along the nose of a nocturnal low- level jet. This jet will initially present itself over eastern Kansas this evening, then intensify and spread into northern Missouri after dark tonight. While instability will be minimal over much of our forecast area, it will perk up toward the Missouri border with MUCAPE of around 1000-1500 J/kg in our far southern counties. While storms are likely from eastern Kansas across northern Missouri in association with the developing LLJ, it is uncertain how far north of the border any storms will be able to penetrate. Given the orientation of the LLJ, the most likely portion of our area to be impacted is in the southeast, roughly south of a line from Mount Ayr to Osky or so, and 40-60% POPs are carried in that area overnight accordingly. Given the aforementioned instability and deep-layer shear of around 30-40 KT, any storms that do reach our forecast area will carry an attendant threat of large hail or strong wind gusts, as outlined appropriately in SPC outlooks.

Any overnight thunderstorms in our area will move off to the east by early Friday morning as the shortwave and LLJ depart, yielding quiet weather for most of the day. The surface trough developing along the lee of the Rockies today will shunt southward as a low centered near the Texas Panhandle on Friday, while a surface high pressure area develops from Montana across the Dakotas and toward northwestern Iowa. This will set up a weak effective warm front likely oriented from west southwest to east northeast somewhere across Iowa by Friday afternoon. Another 500 MB impulse will approach from the west late in the day, and with strong instability pooling into Iowa south of the boundary, present an increasing chance of thunderstorms and severe weather late in the day. Forecast soundings indicate a capping inversion that will need to be overcome, and this will likely not occur until Friday evening and especially Friday night, as discussed further below. Otherwise, the most sensible weather effect on Friday will be much warmer temperatures, as warm air advection and ample sunshine send highs into the upper 80s across the area, with lower 90s even possible in the western half of the state.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/

Issued at 255 PM CDT Wed May 13 2026

Clouds and storm chances return late Friday into early Saturday as a front moves into the state. These storms will be fighting a high pressure in the north and dry air. Models still have a fair amount of disagreement in the south in the timing and location of the next slug of theta-e advection and the LLJ is not favorably positioned. The deep moisture off the Gulf is also shunted off to the east in the low to mid levels potentially pushing the greatest storm threat to the east as conditions were looking this time yesterday, though models are also further north than they were yesterday with ballooning instability and still sufficient shear in southern Iowa. Certainly cannot rule out some strong to severe storms, but the mesoscale details remain a bit too uncertain at this point with refinements likely. The SPC does have a Marginal Risk (Level 1 out of 5) for a good portion of the area and a Slight Risk (Level 2 out of 5) in the far south/southeast on late Friday into Saturday.

The active pattern remains through the weekend with additional storm chances later Saturday into Sunday, and again later Sunday into Monday, and on Monday. SPC has all 3 of these periods (Saturday, Sunday, Monday) with a 15% risk. It is likely that what happens the previous day will somewhat dictate what happens in subsequent days. Will continue to watch these periods closely and provide additional details in the coming days. Temperatures will remain warm and at least in the 80s through the weekend. These temperatures were held down a bit from NBM with NBM on the high end of the temperature distribution and likely affected by storms and cloud debris at times.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 629 AM CDT Thu May 14 2026

VFR conditions will prevail today. SSE winds will increase during the morning, with crosswinds of 20 KT possible on some east-west runways by this afternoon. Scattered showers and a few thunderstorms are forecast across northern Iowa this afternoon and evening, and southern Iowa tonight. Have included PROB30 groups at all terminals except DSM during most likely periods for precipitation, however, the probability of MVFR or lower ceilings/visibilities is quite low (10% or less at any given terminal).

DMX WATCHES/WARNINGS/ADVISORIES

None.