textproduct: Des Moines

KEY MESSAGES

- Extreme Cold Warning this morning for dangerous wind chills of 25 to 40 below zero.

- Cold Weather Advisory noon today through 3 am Saturday.

- Light snow accumulation possible overnight tonight through Saturday, mainly south of I-80.

DISCUSSION

Issued at 259 AM CST Fri Jan 23 2026

A bitterly cold arctic air mass has settled across the area overnight. As of this 2 am writing, temperatures ranged from 0 at Ottumwa to -16 at Mason City with a wind chill of -21 at Ottumwa and down to -44 at Mason City. Wind overnight has been out of the north- northwest gusting 25-35 mph. Temperatures will continue to drop a few more degrees through the early morning with persistent wind. Expect wind chill to bottom out around sunrise in the -40s north and -20s south. Towards midday winds will begin to relax with high pressure sliding across the area diminishing the pressure gradient. Cold air advection also tapers off by midday with a transition to positive theta e advection late today and overnight tonight. The shift to increasing theta e advection is accompanied by increasing mid level moisture and cloud cover, all associated with the large winter storm set to impact much of the southern US this weekend. With lighter wind and warmer (this is a generous use of the word) temperatures this afternoon, reaching a balmy 0 in the south to -10 north (wind chill minus teens south to -20s north), the Extreme Cold Warning this morning will transition to a Cold Weather Advisory around noon. This will remain in effect into the overnight. Temperatures will continue to improve overnight, aided by overnight cloud cover, and the Cold Weather Advisory ends at 3 am Saturday morning.

Overnight tonight and through the day on Saturday of Iowa will be skimmed by the northern edge of the large southern US winter storm. The extent of precipitation into Iowa is uncertain as deep moisture transport out of the Pacific will battle a strong surface high with plenty of dry air. Most models are in agreement that accumulating snow will largely remain south of the I-80 corridor, though how far south is less certain. Despite the dry air north, once saturation is reached soundings indicate an exceptionally deep dendritic growth zone. Omega is modest and often no better than -5 ubar, keeping rates low for any snow that falls. At the same time, a nearly isothermal, saturated profile through the DGZ would allow for high snow to liquid ratios. Current thinking is that parts of far southern Iowa could see an inch or two of light, fluffy snow with a fairly sharp cutoff on the northern side towards the I-80 corridor as dry air wins out. A few CAMs (HRRR/RAP) place this cutoff farther north towards highway 30 or even highway 20, bringing up to 3 inches through southern Iowa to the I-80 corridor. With the amount of dry air expected, this seems overdone at this time.

Temperatures remain cold through the upcoming week with continued northwest flow. Lobes of vorticity rotating down across the area will bring additional shots of arctic cold air, the first of which arrives Sunday night into Monday morning. With each wave light snow chances exist, though with shallow moisture these would be light and may come in the form of HCRs as mentioned in the previous discussion.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 533 AM CST Fri Jan 23 2026

VFR conditions will prevail through the period. Suspended ice crystals are creating a handful of MVFR observations early this morning, however these are due to the extreme cold this morning and not a distinct cloud deck, thus were not been included in TAFs. Breezy north northwest winds continue to gust 20-25 kts this morning. These winds will taper off over the next couple hours. VFR cloud cover will increase late this morning and through the afternoon.

DMX WATCHES/WARNINGS/ADVISORIES

Extreme Cold Warning until noon CST today for IAZ004>007- 015>017-023>028-033>039-044>050-057>062-070>075-081>086- 092>097. Cold Weather Advisory from noon today to 3 AM CST Saturday for IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097.