textproduct: Des Moines

KEY MESSAGES

- Widespread rain arriving today and this evening. Thunderstorms are possible southeast with a non-zero severe threat far southeast.

- Rain transitions to snow from northwest into parts of central Iowa late this afternoon and evening. A narrow corridor of a wet and heavy 1-3 inches is possible.

- Colder with more light snow chances late Friday into Saturday. Gusty winds on Saturday as well.

DISCUSSION

Issued at 416 AM CST Thu Jan 8 2026

Lee side surface cyclogenesis is ongoing over southeast Colorado with a warm front extending east through Kansas and into central Missouri. Strong southerly flow is ongoing in the warm sector of this system with a mass amount of moisture lifting northward from the Gulf. A second and strong short wave is lifting northeast through New Mexico and Texas this morning. That system will lead to a reorganization of the surface low further east into eastern kansas this morning then it will lift northeast into southeast Iowa this afternoon. A 60 kt low level jet will cause the moisture to surge northward into Iowa as this occurs and this will bring a broad rain shield north into the state. In addition, periods with elevated instability move into the southeast half of Iowa this afternoon that may be sufficient for thunderstorms as well. Currently there are two clusters of storms to the southwest over Oklahoma and Texas. While the overall instability is weakening as it arrives into the state, there remain periods of free vertical ascent by uninhibited moist adiabatic lapse rates. There remains a low potential/short time window duration for surface based instability mid afternoon into the early evening. Should this instability be realized, there is the potential for a few low topped supercells with moderate to high low level shear available and perhaps an isolated tornado potential as the triple point lifts through. Sunshine would't be required as the dew point surge may be sufficient to cause this surface based instability.

As mentioned in our last several forecast discussions, while efficient rainfall is expected and areas may receive an inch or more, flooding is not expected. The 7 inch frost depth measured here at the office was completely gone last night and any remaining frost at areas north should quickly dissipate with the rainfall. Certainly ponding of water is expected prior to this occurring. The greater concern late this afternoon and evening is the transition from rain to snow over northwest Iowa. Continue to have a difficult time getting much more than an inch of snow into the grids with this evening, either using the top down approach or utilizing surface wetbulb temperatures assuming no warm layers aloft. Part of this difficulty is determining the exact timing and location of the rain to snow transition then the dry air surge moving in from the northwest, which will cut the precipitation off. There is likely to be a sweet spot where snow can establish for several hours resulting in 1 to 3 inches of snow. Also as previously discussed, the snow crystal morphology suggests a high likelihood of large and wet aggregate snow flakes that could quickly lead to slick and hazardous driving conditions. Should this snow exceed 3 inches, then we start to be concerned with tree limb damage and subsequent power outages. Again, should that occur, it should be a very narrow corridor. At this point, confidence is not high enough to target a Winter Weather Advisory.

Light snow remains possible late Friday and into early Saturday as the next short wave moves through. The moisture availability is low as the Gulf moisture is shunted east with the previous system. Still minor accumulations are possible. The upper closed low descending into the Northern Plains Friday night and Saturday will lead to a strong cold front passage Saturday and perhaps snow showers as some low level instability exists but again limited moisture. Gusty winds are also expected. The NBM continues to have trouble handling this colder air and the timing of warm air advection arrival on Sunday.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1142 AM CST Thu Jan 8 2026

Adjusted time for rain arrival and vsby restrictions from it. Also added a PROB30 group for thunderstorms at KOTM. LLWS will also occur for a few hours as a low pressure system moves just west of the site. The transition to snow happens earlier for northern sites, occurring between 00z and 4z for KFOD and KMCW (later at KALO). 25kt gusts will also become possible once northwest winds prevail. Some improvement from MVFR/IFR possible after 12z in the west.

DMX WATCHES/WARNINGS/ADVISORIES

None.