textproduct: Des Moines

KEY MESSAGES

- Storms this morning will produce small hail, though a few stronger storms may produce hail up to the size of quarters.

- Higher chances for severe storms very late this afternoon into this evening. Large hail and damaging wind gusts will be possible and a few tornadoes may also occur depending on any sunshine.

- Freezing rain potential remains in our far northwest forecast area (Emmet, Palo Alto, northern Kossuth) late tonight into pre-dawn hours of Saturday.

- Breezy and cooler Saturday followed by breezy and warmer on Sunday. Elevated fire weather concerns may develop on Sunday as well given the warm, breezy, and drier airmass.

- Next chance for rain and storms is later Tuesday into Tuesday night.

SHORT TERM /THROUGH SATURDAY/

Issued at 130 AM CST Fri Mar 6 2026

Upper level water vapor imagery shows a trough approaching from the Rockies tonight, which has spawn storms ahead of it across the southern and central Plains. In the low levels, strong warm air advection is ongoing and has aided in storm development and seeing these storms move through central Iowa this morning. Forecast soundings show an elevated warm layer and this will keep storms elevated not surface based. SPC mesoanalysis has shown strong 0-6km shear of around 40 to 50 knots, but this is not being fully realized with effective shear around 30 knots. Most unstable CAPE has been anywhere from 500 to 1500 J/kg with CAPE within the hail growth zone of several hundred up to around 500 J/kg. And hail up to the size of quarters or so is the main concern as these storms first move into the area into early this morning, but so far have had mainly pea sized hail. With forecast soundings showing the column quickly saturating, these moist profiles do not support gusty winds with weak downdraft CAPE and no dry air to entrain into a downdraft. This is confirmed by looking at the wind gust fields from convective allowing models, which show no worse than 40 knots and that seems generous.

While whatever severe threat wanes toward sunrise, showers and a few storms may continue to linger through much of the morning before generally lifting north or northeastward. Models continue to show the trough moving closer to Iowa through the day as an open wave similar to how Thursday afternoon's discussion mentioned. The attendant surface low pressure with this trough will also move east from the central Rockies into Kansas and there will be an elongated low pressure zone setting up into Iowa by late this afternoon into this evening. Surface dewpoints should rise well into the 50s over the state and even low 60s over far southern Iowa with cloud cover remaining stout through the day per HREF, though there could be a few brief breaks here or there. As the synoptic forcing arrives in concert with low level thermodynamic forcing, expect to see a few storm clusters develop late in the afternoon over western Iowa and vicinity. By this time frame, forecast soundings agree there will be strong deep layer shear and sufficient effective shear along with 1000 to 1500 J/kg of surface based instability, but models vary on the level of inhibition/CIN and this presents at least two possible scenarios. First scenario, if there is a bit of sunshine, the CIN may be weaker and allow for surface based severe potential. This would bring tornado potential into play a bit more, especially if the winds can back a bit from what they will mostly be south- southwest much of the day. This is shown in a few models, such as the HRRR and NAMNest, and would increase the low level hodograph curvature. Large hail and damaging winds would be possible as well. Second scenario, inhibition remains too strong to overcome and storms do not root at the surface and remain elevated. This would favor large hail and gusty winds. Regardless of scenario, strong to severe storms are likely with timing remaining largely consistent being late in the day into the evening. Storms are expected to grow into a broken line by this evening and will have to be mindful of mesovortex spin ups on the leading edge with 30 to 40 knots of 0-3km bulk shear. Given the orientation of the 0-3km shear vector, a line acceleration to the northeast would likely be needed to see this generation. Much of this activity will exit our forecast area by midnight or shortly thereafter.

That covers the severe weather concerns on Friday, but now onto the winter weather concerns over northwestern Iowa and our northwestern forecast area Friday night. As the storms pushed off to the east, a cold front will move into the state. Colder air will arrive quicker at the surface than aloft and set up the potential for freezing rain and freezing drizzle. The GFS is slower with the front and thus has little in the way of icing, but the NAM and RAP are the most robust in this potential having 6+ hours of freezing rain with the 0z HREF freezing rain accumulation model (FRAM) showing a tenth of an inch at Estherville. Icing efficiency will be a question as surfaces will be initially wet and have to cool with 4 inch soil temperatures tonight in the middle 30s. Elevated surfaces such as trees and bridges in Emmet, Palo Alto, and northern Kossuth Counties would be most prone to freezing first with roadways likely delayed and impacts in question. Given the uncertainty in how quickly the cold front pushes into the area and icing efficiency, will continue to monitor for possible Winter Weather Advisory issuance.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/

Issued at 130 AM CST Fri Mar 6 2026

Behind the aforementioned cold front, breezy winds from the northwest averaging 10 to 20 mph will deliver drier and cooler, more seasonable air. This cooler airmass will not last long as winds become from the southwest at 10 to 20 mph on Sunday returning the warmth with highs well into the 60s. With the warm, windy conditions, fully cured fuels, and relative humidity values in the afternoon falling to between 30 and 40%, elevated fire weather concerns may materialize. Winds will be not as strong on Monday and may mitigate fire weather concerns with similar conditions otherwise as low pressure tracking over southern Canada sends a cold front into the state with uncertainty in its placement. Initial National Blend of Models (NBM) shows this uncertainty in its temperature forecast with 25th-75th spreads of 20 degrees and run to run inconsistency in its deterministic forecast. While it is still confident to say that temperatures will be above normal, how much will be the question on Monday and Tuesday. As the Baja closed low opens up into the southern Plains late Tuesday, the northern stream trough will begin to push southward towards Iowa. There does look to be theta-e advection ahead of these features that will lift the stalled front back into some portion of the state and bring a chance for showers and storm. Depending on the location of the boundary, there may be appreciable instability and shear for stronger storms in southern or southeastern Iowa with this supported by the AI/ML convective hazard forecasts as well. As the northern stream trough pushes this all out of Iowa Wednesday, should see cooler, but still above normal temperatures somewhere in or around the 50s through the end of the week.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1135 PM CST Thu Mar 5 2026

Timing has been refined for tonight's thunderstorm activity with conditions being dialed back as guidance becomes more clear as to the extent of thunderstorm coverage throughout the morning. Most sites briefly reach MVFR conditions tomorrow pending another round of thunderstorms in the evening. Confidence in showers at the very least is high, but PROB30 has been introduced due to uncertainty in the timing. Low level wind shear was again removed from TAFs due to it being transient and very low end, struggling to reach 30kts.

DMX WATCHES/WARNINGS/ADVISORIES

None.