textproduct: Des Moines

KEY MESSAGES

- Blizzard Warning expanded south and east, plus extended in time until 9 AM Monday. Whiteout conditions from falling/blowing snow expected, leading to dangerous travel.

- Winter Weather Advisory also expanded south and east for reduced visibilities due to falling/blowing snow.

- Freezing rain and black ice potential in southern Iowa as temperatures fall Sunday afternoon.

DISCUSSION

Issued at 348 AM CST Sun Dec 28 2025

The last push of dense fog will be eroded this morning by both the rain to the south and the incoming cold front from the west. The bigger story for Sunday is the blizzard. A two-pronged upper air feature will rapidly deepen across the region today, intensifying a Colorado low. A front associated with the main trough will catch up to the low's cold front, expanding the reach and depth of frontogenetical forcing into northern Iowa today. Temperatures will fall through the day, and a midlevel dry slot will begin to invade southern and central Iowa. In northern Iowa, the frontal circulation will keep the DGZ saturated for most of the event.

Soundings along and south of Highway 30 will have a window of freezing rain from the loss of ice introduction, mainly occurring in the early afternoon hours. This is the lesser talked about threat from this winter storm as it isn't covered by a headline right now, but slick roads will be common as temperatures plummet. Warm road temperatures will stall the black ice possibilities until perhaps the latter half of the afternoon, but the southern half of Iowa may still be dealing with freezing rain until ice introduction becomes more consistent after sunset. A Winter Weather Advisory may be needed later depending on how impactful ice is.

Now for the more advertised portion of this storm: the blizzard. Main change this shift is the expansion of both the Blizzard Warning and Winter Weather Advisory to the south and east. Snow amounts have trended up this forecast with snowfall amounts over 6 inches possible in the far north. Impacts aside from accumulations alone, this means there's even more snow to blow around. The Blizzard Warning covers where there will be at least 2 inches of snow accumulations, driven in part by an extended period of snowfall into Sunday night for the northeast. Profiles remain dendritic as the TROWAL starts to form over northeast Iowa, pulling some of the warm conveyor belt into the lower half of the profiles (aided by a weak front pivoting through). At the same time, CAA keep the PBL mixed overnight. This will keep snow shower potential in play into Monday morning. A sting jet may form on the back side of the rapidly deepening low, evidenced by the 50kt winds found at the top of the mixed layer tonight. This is why winds remain elevated in the northeast overnight, prolonging blowing snow potential. Headlines in northeast Iowa were extended into the morning Monday to account for the extended impacts.

The Highway 30 corridor will have snow amounts between 1 and 2 inches, but the concern is higher snow amounts to the north will be carried to this row of counties in the wind, creating visibility reductions from blowing snow. Profiles remain dendritic overnight as well, with HCR snow showers adding to visibility concerns, just with lighter overnight winds compared to the Blizzard Warning. Enough moisture is present that the snow squall parameter ranges from 1 to 4 along this corridor from midnight to 6am Monday.

In summary: Anticipate challenging to dangerous travel today and tonight, with travel discouraged in northern Iowa. Black ice will be the main concern in the southern half of Iowa as temperatures plummet. Northern Iowa will have the highest gusts, the most snow, and the longest lasting length of snowfall. Snow covered roads will be common, but the bigger and more concerning impact is whiteout conditions from blowing snow. Travel could become impossible in northern Iowa at times Sunday, Sunday night.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 535 AM CST Sun Dec 28 2025

LIFR vsbys and cigs will prevail for much of this period, especially in northern Iowa. The fog will be replaced with blowing snow for northern sites, with prevailing 1/4SM or less vsbys at KMCW and KALO.

For southern sites such as KDSM and KOTM, rain will transition to a mix of freezing rain and snow. Have kept a prob30 for continued freezing rain and snow into the late afternoon hours. Impacts from ice become increasingly likely as temperatures drop through the afternoon. BLSN could impact KDSM at times, highest likelihood in the main window of precipitation. Will need to monitor for additional blowing snow potential after 20z.

DMX WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 9 AM CST this morning for IAZ004>007- 015>017-024>028-036>039-048>050-061-062. Blizzard Warning from 9 AM this morning to 9 AM CST Monday for IAZ004>007-015>017-024>028. Dense Fog Advisory until 6 AM CST early this morning for IAZ023-033>035-044>047-057>060-070>075-081>086-092>097. Winter Weather Advisory from 9 AM this morning to 9 AM CST Monday for IAZ023-035>039-047>050. Winter Weather Advisory from 9 AM this morning to 6 AM CST Monday for IAZ033-034-044>046. Wind Advisory from 9 AM this morning to 6 AM CST Monday for IAZ057>062-070>075-081>086-092>097.