textproduct: Des Moines

KEY MESSAGES

- Freeze and Frost headlines for tonight across portions of central/southern Iowa.

- Warming trend Monday through Wednesday.

- Thunderstorm chances return Wednesday night through Thursday night. Strong to severe storms are possible.

SHORT TERM /THROUGH WEDNESDAY/

Issued at 227 PM CDT Sun Apr 19 2026

Long wave trough that has brought cooler weather to the state the past few days, is beginning to shift off to the east. This will lead to a transition to a warmer westerly/zonal flow aloft. High pressure, centered over southern Manitoba this afternoon, will settle southeast and will be over far eastern Iowa after midnight before and then Illinois by Monday morning. The breezy wind over the state will diminish quickly later this afternoon and into the evening and will lead to a period of radiational cooling, especially over the northeast. Return flow and surface warm advection will begin from west to east as the center of the high pressure moves to the east. In addition, theta-e advection aloft should result in some mid to high level cloud development. Dew point temperatures are expected to be in the teens north to the 20s south and at this time, are expected to maintain a 6 to 10 degree dew point depression. If those depressions remain, the frost potential very well may not materialize. Therefore, there are some challenges with the overnight low temperatures and if radiational cooling can be maintained long enough to shrink the dew point depressions for frost south and drive temperatures low enough for a freeze north. Will maintain the current headlines as is.

Monday will be warmer southerly flow increases, driven by an increasing pressure gradient and deepening mixing to near 875 mb. Despite the warming, the drier air mass will remain with afternoon relative humidity values falling into the 20s and 30s. The recent rapid spring green up with the recent warm weather and precipitation has significantly diminished the fire weather threat across much of Iowa. Thermal ridging arrives over Iowa Tuesday and Wednesday with high temperatures rising back into the 70s and 80s with overnight lows in the 40s and 50s.

LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/

Issued at 227 PM CDT Sun Apr 19 2026

By Wednesday night into Thursday, the dominant pattern shifts to eastern US ridging and western US troughing. As a result, several days of southwest 500 mb flow look to prevail over portions of the central Plains, with Thursday being the main period of interest for Iowa active weather potential. Ensemble suites are in decent agreement of a negatively tilted trough ejecting across the central to northern plains midday Thursday, with the earliest shortwaves/PVA potentially arriving over Iowa on the heels of the retreating ridge Wednesday night. Rapid surface pressure falls will induce strong low level winds and gulf moisture advection Wednesday night into Thursday. Recent EPS/GEFS runs center surface lows over northern MN/Dakotas and West Kansas, sweeping a trailing cold front through Iowa. Deterministic members show at least modest bulk shear and MLCAPE values across the warm sector on Thursday, implying a risk for severe weather. Across the available NCAR, CSU, and NSSL ML models, Iowa is highlighted under higher severe weather probabilities, which is unsurprising given the synoptic pattern. Many numerical models have convective precip associated with lift off the cold front, but details of the evolution of the severe weather risk will need to be refined in the coming days, contingent on wave timing, moisture return, and placement of surface features.

Beyond Thursday, little consistency exists, though most models delay kicking out the trough fully until after Saturday.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1237 PM CDT Sun Apr 19 2026

Scattered to broken cumulus in the 3-4kft range continue to move across the northeastern part of the state today, with rising ceilings through the afternoon and prevailing VFR conditions. Gusty winds from 20-25 knots at a few sites will calm by late afternoon, shifting overnight and becoming southeasterly by morning.

DMX WATCHES/WARNINGS/ADVISORIES

Freeze Warning from midnight tonight to 9 AM CDT Monday for IAZ035>039-047>050-061-062-075-086. Frost Advisory from midnight tonight to 9 AM CDT Monday for IAZ060-073-074-084-085-095>097.