textproduct: Des Moines

KEY MESSAGES

- A 20% chance of a stray shower this afternoon south of I-80, east of I-35 with breezes decreasing into early this evening.

- 20% chance of isolated showers Friday morning over southern Iowa.

- Several chances for showers and/or thunderstorms from Saturday night into next week. There continues to be no apparent signal for significant or widespread severe weather or heavy rainfall with any storm chances.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 145 PM CDT Thu May 7 2026

Early afternoon GOES-East upper level water vapor imagery shows a subtle shortwave trough pushing into the western Great Lakes, which brought the light showers to a small portion of central Iowa this morning. There is still a zone of clouds back into central Iowa with scattered, diurnally driven cumulus developing on either side and a weak radar return nearing Pella. Forecast soundings show a deep boundary layer that attempts to saturate within this diurnally driven cumulus area above the mixed layer and this is also reflected in model QPF from convective allowing models (CAMs) and global guidance. So, have included some low PoPs through the afternoon along and south of I-80 to north of US 34 and as far west as I-35. Given the deep dry subcloud layer, will be on watch for gusty winds, but downdraft CAPE values and CAM wind gust fields are not alarming. Dewpoints were once again lowered this afternoon to account for the boundary layer mixing, which lowers relative humidities (RHs) over western and northern Iowa to around or below 20%. Fortunately, winds in the mixed layer are no more than 25 knots and combined with the greening fuels, there are no elevated fire weather concerns.

While the night will start mainly clear, clouds will increase ahead of the next push of forcing. Similar to last night, temperatures may fall quickly after sunset before stabilizing as clouds arrive. There may once again be some patchy frost, but less coverage than the past two nights being confined to isolated areas of north central into northeastern Iowa. As the forcing arrives toward sunrise Friday via weak QG convergence and theta-e advection, a low chance of showers may develop over southern Iowa in the morning hours. Saturation will once again be a challenge per forecast soundings, but there is enough support in the model QPF fields to increase PoPs over the initial National Blend of Models up to slight chance. This will scoot away by the afternoon with decreasing clouds. With the deep boundary layer mixing again, have lowered dewpoints as low as the 10th percentile of model guidance in the afternoon based on the RAP and HRRR, which tend to perform well in these environments. This results in RHs below 25% from a similar line of Atlantic to Ames to Waterloo. Winds will increase in the afternoon over northern Iowa, but nothing of concern for elevated fire weather conditions given the green up.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 145 PM CDT Thu May 7 2026

Broad cyclonic flow will continue over the region this weekend into early next week as the closed, upper low gyre continues over Hudson Bay and eventually moves away from it. This will keep temperatures around seasonal levels if not generally above normal. In addition, there will be shower and/or storm chances in at least some portion of Iowa every 36 to 48 hours starting Saturday night through about the middle of next week. As indicated by the previous discussion, the next shortwave trough is staying the course this model cycle being more focused over Missouri Saturday night. Compared to this time yesterday, QG convergence and theta-e advection is now maximized south of Iowa, though may still see a few showers sneak into far southern Iowa with those chances up to around 30% - about 30 to 40% lower than this time yesterday. The next chance for showers and storms arrives late Monday into Tuesday morning. Kinematics are impressive with a strong low level jet, but instability is marginal owing to the nighttime passage of the system pointing to perhaps strong to a few severe storms. This is in line and continues to be supported by the GFS/EC forced ML/AI severe probability tools with no widespread severe weather threat apparent. Wednesday and beyond, pattern agreement deteriorates leading to lower confidence in additional storm chances.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1227 PM CDT Thu May 7 2026

VFR conditions will continue through the end of this TAF period. Winds are expected to be light and variable overnight at terminal sites. Clouds will move in near daybreak tomorrow for OTM, and DSM bringing ceilings down to 10,000ft. There will be a slim chance for a shower near OTM at the end of this TAF period but confidence is not high enough to mention it at this time.

DMX WATCHES/WARNINGS/ADVISORIES

None.