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FXUS63 KDMX 192352 AFDDMX

Area Forecast Discussion National Weather Service Des Moines IA 652 PM CDT Sun May 19 2024


Updated for the 00z Aviation Discussion

KEY MESSAGES

- Active pattern to persist through early next week with multiple rounds of thunderstorms, some of which may be severe

- Tuesday carries the most widespread and high impact severe weather potential with widespread Enhanced Risk (3/5)

- Storms will likely be accompanied by heavy rain through Tuesday as moisture increases

DISCUSSION
Issued at 247 PM CDT Sun May 19 2024

Progressive pattern continues through early this week with multiple shortwave troughs lifting northeast across IA.
Periodic thunderstorms will be the result with varying severe weather threats, some of which will depend upon overnight convection and the impact on insolation/instability.

Elevated storms have been pesky today, maintaining for longer and stronger than most models had indicated. The more organized updrafts have hugged a MUCAPE gradients thats draped across southern IA. Convection has been isolated and weaker elsewhere.
Expect this trend to continue for the remainder of the afternoon. Looking upstream, satellite clearly depicts next shortwave accelerating across the high plains, with convection erupting in advance. This shortwave tracks across the state later today and overnight, providing the next potential (this evening) for severe convection give sufficient deep layer shear and instability. Thunderstorms will linger through the overnight; although severe threat decreases later this evening.

Shortwave trough moves east of the CWA on Monday morning, likely providing a relative minimum in storm chances immediately in its wake, sometime around midday. Even so, surface boundary will remain draped across the state and when combined with SBCAPE values of 2000-2500 j/kg will provide the potential for another round of afternoon/early evening convection. Coverage/strength will depend on how quickly the morning shortwave departs and how much destabilization can occur behind.

Attention then shifts to Tuesday as the strongest shortwave of the period takes aim on the Midwest during diurnal heating.
Latest guidance tracks the surface low pressure into NW IA or S MN by mid-afternoon. Parameters are progd be more than sufficient for severe in the warm sector with SBCAPEs progd 3000+ j/kg and deep layer shear of 50-60 knots. There is some questions on timing and location of synoptic features, which will dictate where storms initiate and resultant impact on severity. As always, the devils in the details, which will become more clear in the next 24-36 hours.

The system departs quickly Tuesday night, giving way to a couple of drier days on Wednesday and Thursday. More storm chances returning by the end of the week.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
Issued at 652 PM CDT Sun May 19 2024

A line of showers and storms remain over northeastern Iowa, which are expected to move over KALO over the next hour or two before drying for a short time. Additional more widespread showers and storms are expected to develop later this evening and lift across the state overnight and through much of Monday morning. Lowered ceilings in combination with periods of heavy rainfall is expected to allow for potential MVFR conditions at times across the terminals. A period of drier conditions looks to return after 15z-18z and into the afternoon, before more showers and storms return towards the end of the period.
Uncertainty on exact timing and coverage, especially towards the latter portions of the TAF period will likely be lower over the next few forecast packages as details become at least a bit more clear with these multiple rounds of showers and storms.
Outside of potential gusty winds at times with any storms, winds gradually shifting south/southwesterly are expected at speeds up to 15 knots.

DMX WATCHES/WARNINGS/ADVISORIES
None.

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Des Moines, IA,