textproduct: Des Moines

KEY MESSAGES

- Gusty winds this afternoon may result in blowing dust with elevated fire weather conditions in northern Iowa.

- A few showers and storms possible in far northern Iowa through early this evening, which will not be severe. A severe storm or two may develop or move over far southern Iowa later this evening with hail and gusty winds the main concerns.

- Warm with multiple periods of severe storm potential Friday evening into early next week. The first storm period is Friday evening into the night with large hail and damaging wind gusts possible. Severe and heavy rainfall details beyond Sunday become fuzzy due to compound convective events increasing uncertainty.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 157 PM CDT Thu May 14 2026

GOES-East upper level water vapor imagery shows a plume of moisture spreading from the High Plains eastward over our region this afternoon as a tightly wound up low pressure over the Saskatchewan province moves in a similar direction. This moisture is reflected in the cloud cover that has spread over parts of the western half of the state through early this afternoon. There have a been a few showers or storms late this morning that reached western Iowa, but dry low levels per forecast soundings and dewpoint depressions around 30 degrees is limiting much of this from reaching the ground. That may change through the remainder of this afternoon and early evening over far northern Iowa as a wave of low level theta-e advection moves across on the leading edge of the instability gradient perhaps allowing for spotty showers and a few non-severe storms. With surface high pressure retreating to the Ohio Valley, the upstream low pressure is tightening the pressure gradient over the state. Thus, winds are once again gusty and combined with the dry air and resultant low relative humidity, elevated fire weather conditions are present over northern Iowa. Critical fire weather conditions are kept at bay as cool season grasses have greened, though observations from US Wildland Fire partners indicate warm season grasses are still cured and would be most susceptible to carrying a fire. In addition, as we have seen the past few days, may have blowing dust, especially next to any recently plowed or tilled farm fields. For now, have issued a Special Weather Statement over northern Iowa to cover the wind, elevated fire weather conditions, and potential blowing dust into early this evening.

Another chance for storms develops mid-evening into the first few morning hours over Missouri into far southern Iowa as the low level jet (LLJ) points into this region and a weak 500mb shortwave trough lifts east-northeastward through the region. Isolated storms that do develop or move up into southern Iowa will be elevated above an inversion per forecast soundings with MUCAPE shown between 500 and 1000 J/kg and deep layer shear of 30 to 40 knots supportive of isolated hail and gusty winds risk. Guidance from 0z to 12z and recent HRRR runs have shown a general southward shift in the area, though the 12z HRRR still maintained some risk over southern Iowa.

Friday will be a warm day as our low level flow becomes more or less established from a southerly direction, which will persist into early next week. Temperatures will soar well into the 80s to near 90 degrees with lighter winds as a surface boundary pushes into Iowa from the north, which is associated with the southern Canadian prairie low pressure. The southerly flow will increase dewpoints well into the 50s to near 60 degrees south of this boundary. As the LLJ points into Iowa Friday evening and another shortwave trough lifts into the region, storms will either initiate on the nose of the LLJ or along the boundary with the former shown in the convective allowing models (CAMs) and the latter shown more in the global models. The environment Friday night is favorable for isolated to scattered severe storms with MUCAPE values over 1500 J/kg, steep mid-level lapse rates up to around 8C/km, and deep layer shear over 30 knots. Forecast soundings continue to show an inversion, which keeps storms elevated. This is good news as hodographs will not be able to take advantage of low level curvature and thus focus hazards on large hail and damaging wind gusts from Friday evening through perhaps 3 or 4am Saturday with the highest risk area in Iowa along and south of Iowa Highway 3 (roughly Storm Lake to Waverly) and points south.

LONG TERM /SATURDAY THROUGH THURSDAY/

Issued at 157 PM CDT Thu May 14 2026

As we move into the weekend, current expectation is that Saturday morning will be a drier period compared to later in the day. The boundary that pushed into Iowa on Friday will be lingering over the state in some west to east fashion. While temperatures everywhere will be in the 80s, dewpoints well into the 50s and low 60s will pool south of this boundary. Instability will build beneath an elevated inversion, which should inhibit storm development until later if not late in the afternoon as waves of weak to modest theta- e advection move overhead. Mixed layer CAPE values over 2000 J/kg, around 30 knots or a bit above for deep layer shear, steep mid-level lapse rates, and low level curvature in the hodographs point to severe storm potential. Any storms that can develop in the late afternoon or evening may become strong with large hail and damaging wind gusts the main hazards. In addition, storm motions as low as 10 mph up to around 25 mph may result in locally heavy rain swaths. However, any flash flood threat will be relegated to an urban area due to 0-10cm and 0-40cm NASA SPoRT soil moisture no higher than the 20th percentile and generally less than the 10th percentile. Therefore, there should be capacity in soils to absorb this rainfall, which for many will be welcomed given our recent dry weather. In addition, a tornado threat may also develop in the vicinity of the effective front, but there is a lack of a surface low nearby driving stronger low level flow, which is reflected in the the low storm relative helicity values and poor streamwiseness.

The storms Saturday evening will move away with details in the forecast become fuzzy into early next week as successive convective events compound uncertainty and model consensus diverges. It does look like a mesoscale convective system (MCS) develops somewhere upstream of Iowa Saturday night and may move across some portion of the state late Saturday night into Sunday morning. After any storms with the MCS move out Sunday morning, it looks like we could stay capped through much of the day with warm and windy conditions, but this will depend on where the MCS tracks and any boundaries or convective debris left behind. Storms may develop in the LLJ over Iowa Sunday night, but a higher risk of severe storms and locally heavy rainfall may develop Monday afternoon and evening as low pressure and stronger forcing moves over Iowa. However, the ECMWF and CMC are slower than the GFS and this is also shown in the ensemble 500mb data as well. This could have storm potential linger into Tuesday. After the boundary does push through the state, whether Monday night or sometime Tuesday, cooler and drier air will move into the state along with less stormy conditions.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 658 PM CDT Thu May 14 2026

Broken mid level cloud cover will continue to push east across Iowa tonight, with a few showers and storms expected to pass at/near KMCW within the hour before dry conditions return. Additional showers and storms however are still possible over southern Iowa late tonight into early Friday near KOTM where PROB30 mention remains reasonable for this issuance. Breezy south/southeasterly winds will gradually decrease into Friday, with clouds departing through the morning. VFR conditions are expected across the terminals through the period.

DMX WATCHES/WARNINGS/ADVISORIES

None.