textproduct: Des Moines

SHORT TERM /THROUGH SATURDAY NIGHT/

Issued at 341 AM CDT Fri Jun 12 2026

Currently the main relevant feature across North America is the trough/surface low sitting nearly stationary near the Hudson Bay in Canada. The shortwave that brought storms across the Midwest yesterday has advanced to the Great Lakes, trailing a cold front and igniting deep convection from Michigan to Texas, visible this early morning on the GOES infrared channel. 30 knot 850mb flow across Iowa is putting in work to advect in dryer dewpoints near 3C. Height rises out west should continue filling in this morning through the day. High pressure and fair conditions will prevail Friday. Friday will remain dry, with meager dewpoints in the 50s and 60s. Ample sunshine, dry air, and cold air advection regime subsidence will allow for deep mixing of winds aloft. Winds in northern IA could gust up to 20-25 knots. Highs will be modest in the low to mid 80s.

By Friday night/Saturday morning, the pattern remains progressive and another shortwave will pivot around the Hudson low through Montana and the Dakotas. 500mb flow increases on Saturday around the base and exit region of the shortwave. A NE to SW oriented cold front, stretched from the Hudson low to west plains lee cyclogenesis, moves across the state throughout the day Saturday, with guidance suggesting the front begins to move already by 12z- 15z. This may provide lift for storms in northern Iowa after 12z. Moisture return will be delayed, with uncertainty in timing. However, the HRRR suggests a moist layer in the 700-850mb layer could create 2000 J/kg of elevated CAPE, but is the most bullish on moisture return. Nevertheless, many of 00z suite CAMs have scattered thunderstorms along and ahead of the front Saturday morning, with varying levels of organization. Shear for severe storms is still uncertain, as CAMs suggest 1-6km shear in the vicinity of these storms could be anywhere from 20-50 knots.

By Saturday afternoon, the front continues southeast, sitting over DSM by early afternoon. REFS suggests more robust thunderstorm development begins between 18z-21z and moving southeast, though this may play out in a few scenarios. Firstly, there is uncertainty in the northward extent of moisture return. REFS guidance brings 70s dewpoints into the southeast third of Iowa by 18z-20z, but many of the other CAMs focus the northern extent of dewpoints over northern Missouri. One reason may be the impact of morning convection. The HRRR, a more southern solution, develops an MCS across SE IA and in NE MO that pushes out an outflow boundary (OFB) and confines better moisture to Missouri. The RRFS, however, doesn't develop any convection and brings moisture much further north. Let's assume a fairly organized morning MCS is an outlier at this point given the placement of the stronger LLJ nose in Missouri. Between 21z areal RAP/RRFS/HRRR soundings across south central Iowa, large uncertainties still remain in the storm environment. CIN magnitude is varied ahead of the cold front, and this would affect the likelihood of traditional warm sector CI. Still, many of the CAMs initiate supercells ahead of, along, and perhaps behind the front before growing upscale as they push into Missouri. Given moderate to strong MUCAPE, robust updrafts supporting large hail and damaging downdrafts are possible. This is even the case in the post frontal region, as the thermodynamic changes on the cold front are diffuse. The degree of effective shear also varies widely across forecast profiles. However, HREF/REFS guidance suggests 500mb flow of 40-50 knots, which will generally produce enough effective shear for supercells or MCSs. Most models suggest low level winds will be somewhat veered in southern IA, especially given the weak LLJ and lack any any nearby surface low. However, the some solutions hint at a stronger LLJ, better pressure falls nudging into SW Iowa, and possibly an OFB. All of which would result in better low level shear and locally high tornado threat with any supercells that may form ahead of the cold front. The lack of a continuous LLJ and progressive nature of the cold front would suggest a lesser hydro threat, but some CAMs still produce several inch QPF swaths across an already well saturated southern Iowa, so a poorly placed complex of upscale growth could renew flash flooding concerns.

LONG TERM /SUNDAY THROUGH THURSDAY/

Issued at 150 PM CDT Thu Jun 11 2026

High pressure fills in again behind the Saturday wave, resulting in mostly dry conditions through Sunday and into the beginning of next week. Temperatures will be milder through this period, with highs in the mid 70s on Sunday and upper 70s on Monday. As we get into the middle of next week, the pattern turns a bit more active again, but there's plenty of time to hash that out in the coming days.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1044 PM CDT Thu Jun 11 2026

VFR conditions will prevail through the TAF period. West winds through the day on Friday will shift to out of the south by around 00z.

DMX WATCHES/WARNINGS/ADVISORIES

None.