textproduct: Des Moines

KEY MESSAGES

- Strong and gusty winds and dry conditions are forecast Thursday, especially in southwestern Iowa where a Red Flag Warning has been issued.

- Even stronger winds are forecast Thursday night, especially across northern Iowa where gusts to around 60 MPH are possible and a High Wind Watch has been issued.

- Confidence in a potentially significant winter storm this weekend is steadily increasing. However, the track of the system and any resulting heavy snowfall is still coming into focus. At this time the most likely area for most significant impacts is across parts of Minnesota, Wisconsin, and northern Iowa, but any changes to the forecast track would significantly impact this potential. Stay tuned to forecast updates in the coming days.

SHORT TERM /THROUGH SATURDAY/

Issued at 230 PM CDT Wed Mar 11 2026

A band of light snow, mixed with rain in some areas, moved through central Iowa this morning and is now exiting our eastern and southeastern counties. Any additional snow accumulation or impact will be negligible. Meanwhile, north northwest breezes and lingering cloud cover are keeping temperatures notably cooler today than on previous days, though rapid clearing will allow temperatures to rebound to some extent this afternoon and melt much of the snow that fell this morning. A surface ridge will then slide across the High Plains and Iowa tonight, resulting in diminishing and backing winds and mostly clear skies overnight. A weak mid-level impulse will be traveling over Minnesota, Wisconsin, and northern Iowa overnight and may generate some clouds there. Some models are spitting out small/light QPF bullseyes in an attempt to generate sprinkles/flurries, however, forecast soundings illustrate considerable dry air below any cloud layer and a dry forecast has been maintained accordingly.

On Thursday neutral northwesterly 500 MB flow will be in place over Iowa, while an intense and elongated trough stretches from far southwestern Canada over to North Dakota by the afternoon. A surface trough will deepen rapidly across the northern High Plains in response to this approaching system, even as the aforementioned surface ridge moves away to our southeast over the Ohio River valley. Between these two systems a tight pressure gradient will promote strengthening south southwest winds across our service area, as well as low-level warm air advection that will send temperatures rising into the 50s to lower 60s on Thursday afternoon. Most model output shows winds nearing advisory criteria, most prominently the HRRR which (on the 12Z run) depicts a large area of 40-45 MPH gusts crossing our area in the afternoon. However, there are some mitigating factors to consider. One is that with the wind direction and warm air advection regime, downward momentum transport will not enhance the mixing and climatologically advisory criteria is more difficult to reach in these situations. Another is that mid- level clouds will gradually thicken during the day ahead of the system approaching from the northwest, which will also suppress turbulent mixing to some extent. Given these detracting factors and the marginal nature of the forecast values relative to advisory criteria, a Wind Advisory has not been issued and we will continue to monitor short-term forecast trends in case one becomes warranted overnight. The strong winds and dry conditions will also promote a critical fire weather danger in our southwestern counties on Thursday, and a Red Flag Warning has been issued for that area. These concerns are discussed in more detail in the FIRE WEATHER section below.

On Thursday night the intense 500 MB trough will deepen further and dig southeastward across Minnesota and Wisconsin, scraping northern and northeastern Iowa as it passes. This system will push a strong surface trough southeastward through Iowa on Thursday night, causing winds to turn from southwest to west northwest and strengthen even further overnight. The surface pressure gradient in our area will remain fairly tight but loosen a little through the night, however, behind the surface trough there will be substantial pressure rises as well as multiple hours of strong low-level cold air advection. With the strongest 925 MB winds and steepest pressure rises occurring over northern Iowa, closer to the parent system, the strongest surface winds and gusts are also expected in that area with only a gradual diminishment farther south. The only question is just how strong the winds will get, and how far south. It is a classic set-up for a High Wind event, with the only mitigating factor being time of day which will limit mixing depth. However, even the NAM which has the shallowest mixed layer Thursday night still shows winds of 42-48 KT at the top of the mixed layer in our northern counties, which is near warning criteria. Several other models, including the GFS which depicts top of the mixed layer winds of 60-70 KT across our north, and the HRRR which (on the 12Z run) depicts widespread 50-55 KT surface gusts in the north. In light of the high confidence in synoptic conditions and the potential for criteria to be significantly exceeded, have issued a High Wind Watch for areas along and north of Highway 30 Thursday night. It is quite possible this will need to be upgraded to a Warning, and perhaps expanded southward or with an Advisory issued to the south, at some point tonight or tomorrow.

Strong and gusty winds will persist into Friday morning, then rapidly diminish later in the day as a high pressure ridge builds in quickly from the northwest during the afternoon. This will provide a brief window of quieter weather Friday afternoon and evening, and while temperatures will be cooler behind the overnight front and with the high building in, sunshine and diminishing winds should still allow temperatures to rise into the 40s across most of the forecast area. From Friday night through Saturday, the first storm system will be departing far to our east while yet another 500 MB trough digs quickly across the northern U.S. Rockies. As a result, the steering flow over Iowa will back from northwesterly to west southwesterly during this time, and a band of isentropic lift and warm air advection aloft will set up from around South Dakota across parts of Minnesota and Iowa. As this swath gradually develops and the lift within it gradually increases, light precipitation will become steadily more likely in the period from around Friday evening to Saturday evening, and thermal profiles generally support snow as the most likely precipitation type. However, there are two mitigating factors to consider. The first is that initially, the aforementioned surface high pressure area building into the region on Friday will remain in place and any light precipitation generated by the relatively weaker forcing is less likely to reach the surface or accumulate, thus only 20-30% chances are carried Friday night into Saturday morning. The second factor is that even by Saturday afternoon and evening as the column becomes more saturated and forcing for ascent continues to increase, there are discrepancies among model solutions as to how far north the swath of developing precipitation will be by that time. Therefore, while 30-40% chances are carried in our northern counties later Saturday, our southern counties are dry at this time pending additional analysis in the coming days.

LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/

Issued at 230 PM CDT Wed Mar 11 2026

A significant winter storm is possible across portions of the Upper Midwest between Saturday night and Sunday night. As mentioned in the Short Term discussion above, a 500 MB trough will dig over the northern U.S. Rockies on Saturday. Subsequently, it will further intensify and dig southeastward over the latter half of the weekend, becoming nearly positively tilted near the Upper Mississippi River valley by Sunday night. A strong surface cyclone will develop rapidly in response to the approaching mid-level system, initially near the Kansas/Colorado border Saturday evening and eventually tracking somewhere over Missouri/southeastern Iowa/Illinois around Sunday morning or so. The swath of developing snowfall discussed in the Short Term section above will initially be most likely over our northern and northeastern counties late Saturday, then pivot and sweep southeastward later Saturday night and Sunday. There is high confidence in precipitation during this time and POPs have been increased to 70-80% across nearly our entire forecast area. Also, confidence continues to increase that on the northern periphery of the developing cyclone, where the initial swath of snow will begin earlier and where colder temperatures will allow for more snow to fall as the system passes, a significant winter storm may unfold with heavy snow and strong winds expected. However, where confidence has not increased today is in the track of the low and associated temperature fields, which will have critical implications for forecast snowfall amounts and impacts. With the surface low tracking near or over southeastern Iowa, much of the precipitation across the southern half or so of our area may initially fall as rain, limiting snow accumulation potential, while in northern Iowa or especially Minnesota and Wisconsin heavier and more prolonged snowfall is expected. At this time our northern and northeastern counties appear more likely to fall into the latter category than the former, however, given the degree of model variability in resolving the track of the system and sub-freezing profiles at the current range of about 4 days, no watches have as yet been issued in Iowa for this system. We will be closely monitoring it in the coming days, and anyone planning travel around or into central or northern Iowa and neighboring states should watch for forecast updates and possible watches or warnings in the coming days.

FIRE WEATHER /THURSDAY/

Issued at 230 PM CDT Wed Mar 11 2026

As discussed in the Short Term section above, gusty south southwest winds are forecast on Thursday, with speeds near 25 MPH and gusts to around 40 MPH possible in the afternoon. Concurrently, relative humidity will decrease rapidly after sunrise and in our southwestern counties, reach levels of around 25% in the afternoon and evening resulting in a critical fire weather danger and a Red Flag Warning in that area. However, there are still some uncertainties and limiting factors to consider. Low-level warm air advection, along with thickening mid-level clouds, will mitigate wind strength and could keep speeds from quite reaching warning criteria especially to the northeast of the current RFW. Also, the clouds and recent light snowfall that has melted may keep relative humidity closer to the 30% level and provide some dampness to surface fuels. These mitigating factors are less likely to impact our southwestern counties where the RFW is in effect, but may result in "only" elevated fire weather concerns farther east into central and southern Iowa. We will be closely monitoring short-term forecast trends tonight in case an expansion of the Red Flag Warning becomes warranted. In any event, any fires that start Thursday will have the potential to spread rapidly, especially in southwestern Iowa but possibly farther east as well.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1220 PM CDT Wed Mar 11 2026

The band of snow that brought low ceilings and visibility this morning is beginning to work it's way out of the area. The band has moved out of KALO and will be moving through KOTM shortly. Once it departs, trailing MVFR clouds are expected to linger into the afternoon before skies clear late this afternoon and evening. Winds will be breezy out of the north northwest this afternoon, with gusts of 25 to 30 kts ongoing. Winds will diminish overnight, becoming more westerly then southerly by Thursday morning. Winds become breezy again through mid-day Thursday.

DMX WATCHES/WARNINGS/ADVISORIES

Red Flag Warning from Noon to 9 PM CDT Thursday for IAZ044-045- 057-058-070-071-081-082-092-093.

High Wind Watch from Thursday evening through Friday morning for IAZ004>007-015>017-023>028-033>039-044>050.