textproduct: Des Moines

KEY MESSAGES

- Red Flag Warning in the southwest through this evening for critical fire weather conditions. Near-critical conditions near the warning area.

- Strong winds and scattered showers tonight. High Wind Warning in effect central and north for gusts potentially 60+ mph tonight. Wind Advisory south for wind gusts near 50 mph through tonight.

- A significant winter storm will impact the region this weekend with heavy snow, strong winds, and blizzard conditions all possible between around Saturday night and Sunday night. However, the location of heaviest snowfall and highest impacts is most likely across Minnesota and Wisconsin, with confidence steadily decreasing southward across Iowa. A Winter Storm Watch has been issued for far northern Iowa.

SHORT TERM /THROUGH FRIDAY/

Issued at 237 PM CDT Thu Mar 12 2026

A dynamic 500 MB trough is rapidly deepening as it moves quickly east southeastward across North Dakota this afternoon. A surface cyclone is quickly spinning up in response. Ahead of the system a broad area of warm air/moisture advection aloft and forcing for ascent is producing thickening clouds across the Dakotas, Minnesota and Iowa, while a strengthening pressure gradient is supporting increasing south southwesterly winds across our area. The combination of strong winds and dry conditions is supporting both the Wind Advisory and Red Flag Warning in effect for portions of southern into western Iowa this afternoon.

Tonight, a sharp surface trough trailing from the developing cyclone to our north will sweep across Iowa. Ahead of this trough, as a tight low-level pressure gradient surrounding the low moves through, several high-resolution models are indicating southwesterly winds increasing further across parts of southern and eastern Iowa, for example the RAP shows 925 MB winds surging into the 50-60 KT range in our southeastern half or so around 01-05Z, though with mixing depth diminishing it is difficult to tell how much of this will translate to surface gusts. The Wind Advisory in effect for our southern counties this afternoon is carried through the night accordingly, with the High Wind Warning farther north beginning at 03Z. Increasing lift and deepening moisture in the column will also allow for rain showers to develop and move through our forecast area, particularly the northeastern half closer to the parent system. As the surface trough surges through overnight, winds will then shift to west northwest and increase even further, especially across the northern half of Iowa where pressure rises and 925 MB winds will be strongest, and supported by another tight pressure gradient and strong cold air advection. While some deterministic models have backed off slightly on surface wind speeds and gusts in the north overnight, the bulk of solutions and the synoptic set-up still clearly favor wind gusts to around 60 MPH in the north, and the High Wind Warning remains in effect. It should also be noted that as showers move through this evening and early tonight, they may add in downward momentum transport and support brief periods of enhanced gusts especially within the warning area.

LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/

Issued at 237 PM CDT Thu Mar 12 2026

On Friday the storm system to our north will move rapidly away over the Great Lakes region, replaced by a surface high pressure ridge building from Minnesota down into Iowa by the end of the day. This will support quieter weather with rapidly diminishing winds Friday morning into the afternoon. Unfortunately this brief quiet period will be far too short, as by Friday evening an even more impactful storm system will be entering the western U.S. Initially, brisk 500 MB flow will be from the west northwest over Iowa, then on Saturday as a highly energetic trough digs into the northwestern U.S., the flow over Iowa will pivot to zonal/westerly, then southwesterly by Saturday night as the trough quickly approaches. From Friday night into Saturday, a subtle mid-level impulse and associated isentropic lift will scoot eastward across the region, spreading a band of light snow across parts of our area. Initially it will be fighting low-level dry air within the high pressure ridge, but as the ridge subsequently moves away to the east snow should fall most likely across our northern counties, but with some flakes possible farther south as well. Limited moisture and forcing will preclude any heavy precipitation and only minimal snow accumulations are anticipated, but there could be some spotty travel impacts late Friday night into Saturday morning, mainly across northern Iowa.

While the light snow will move away Saturday morning, it will prove only a tiny sample of what is to come as the aforementioned strong 500 MB trough moves off the Rockies Saturday night and Sunday. The surface low spinning up along its forward flank will cross Kansas Saturday night, then track across Missouri, southeastern Iowa, and Illinois on Sunday. All signs point to a widespread, significant precipitation event along the northern and western hemisphere of this low, and POPs are near 100% accordingly. The area of most significant impact will be within the TROWAL region that develops along the northwestern periphery of the cyclone, where enhanced and prolonged lift and colder temperatures will allow for a swath of potentially very heavy snowfall. Farther south and closer to the low, relatively warmer near-surface air wrapping around the system will make precipitation types more mixed, with rain, thunderstorms, a wintry mix, and snow all possible at times. This will reduce overall snow amounts closer to the low, but at least some travel impacts are still likely. The primary question as it regards potential hazards, then, is where precisely the low center will track, when and where the TROWAL will develop, and where the resulting swath of heavier snowfall accumulations will lie. The bulk of model solutions have consistently painted this swath across the southern half of Minnesota, Wisconsin, and far northern and northeastern Iowa. However, with the system still more than two days out and actually not even having entered the western U.S. observational data network yet, a northward or southward shift is still entirely possible. In conjunction with the threat of heavy snow, very strong winds are also once again forecast on the backside of the passing cyclone, with forecast soundings already depicting top of the mixed layer winds around 55-65 KT across northern Iowa. Wherever the swath of heaviest snow falls, these very strong winds will greatly exacerbate impacts which could be severe. Given the potential for significant impacts due to possibly heavy snowfall along with the strong winds, have issued a Winter Storm Watch for our far northern counties, where both confidence levels and potential magnitude of impact are highest, and we will be assessing for possible expansion and/or upgrade over the next couple of days. This winter storm system bears very close watching for any residents across the region, especially those with any travel plans between Saturday night and Monday.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 652 PM CDT Thu Mar 12 2026

The main aviation concern this period are the windy conditions as a cold front moves through the state tonight. Ahead of the front, winds from the south and southwest will prevail at 15 to 25 knots with gusts up to 30 knots. This front may bring light rain showers to MCW and ALO for two or so hours with lesser confidence in FOD/DSM so have used PROB30 as those terminals. In addition to the surface winds, low level winds are also strong and will create a short period of low level wind shear as the front passes a terminal with winds from the southwest becoming from the northwest. As the surface winds strengthen behind the front, this will end the LLWS concerns. Surface winds behind the front will be sustained at 25 to 35 knots with gusts of 45 to 55 knots expected after midnight through mid-morning. Thereafter, winds will diminish through the day and be sustained at 7 to 14 knots by the end of the period. Finally, probabilities are increasing for a short period of MVFR ceilings at MCW late tonight/early Friday morning so have included those and may have to expand to ALO if trends continue.

DMX WATCHES/WARNINGS/ADVISORIES

High Wind Warning from 10 PM this evening to 7 AM CDT Friday for IAZ004>006-015-016-023>025-033>035-044>047-057>059. Winter Storm Watch from Saturday evening through Monday morning for IAZ004>007-015>017-023>028. High Wind Warning from 10 PM this evening to 10 AM CDT Friday for IAZ007-017-026>028-036>039-048>050-060>062. Red Flag Warning until 9 PM CDT this evening for IAZ044-045- 057-058-070-071-081-082-092-093. Wind Advisory until 7 AM CDT Friday for IAZ070>072-081>083- 092>094. Wind Advisory until 10 AM CDT Friday for IAZ073>075-084>086- 095>097.