Snow

Numerical weather prediction guidance continues to indicate a general consensus among the primary global models—including the UKMET, ICON, ECMWF, GFS, and GDPS—that the primary corridor for significant winter weather will remain displaced to the north of the immediate region. While there has been notable run-to-run variability over the past 24 hours, particularly with respect to the amplitude and latitudinal placement of the surface low and associated mid-level trough, the most recent model cycles have converged toward a predominantly northerly storm track.

Despite this increasing agreement, forecast confidence regarding the exact placement of the storm system remains moderate at best. The magnitude of recent model shifts underscores lingering uncertainty in the evolution of the synoptic-scale pattern, including the timing and phasing of upper-level energy and the resultant thermal gradients. As a result, small adjustments in the track could still lead to meaningful changes in sensible weather outcomes, particularly along the southern gradient of the snow shield.

In coordination with this evolving guidance, the National Weather Service has issued a Winter Weather Watch for portions of eastern Missouri and southwestern Illinois. The watch is currently valid from Friday night through Sunday morning for the following forecast zones: ILZ064, ILZ065, ILZ069, ILZ070, ILZ074, ILZ079, ILZ100–ILZ102, MOZ047–MOZ049, MOZ059, MOZ061–MOZ065, and MOZ072–MOZ075 (NWS product identifier: /O.EXB.KLSX.WS.A.0001.260124T0600Z–260125T1800Z/). This issuance reflects the potential for impactful winter weather, including accumulating snowfall and hazardous travel conditions, should the storm track verify as currently depicted.

From a dynamical standpoint, the anticipated precipitation is associated with a southward intrusion of Arctic air driven by a strong polar jet streak, interacting with a broad moisture plume originating from the Gulf of Mexico and, to a lesser extent, the eastern Pacific. The juxtaposition of this cold, dense air mass with relatively warm, moisture-rich air is expected to enhance frontogenetical forcing and upper-level divergence, supporting the development of a widespread precipitation shield along and north of the storm track. Thermal profiles across the region will ultimately determine precipitation type, with snow favored on the cold side of the system.

Forecasts will continue to be refined as additional observational data are assimilated and model guidance further resolves the evolution of this system. Interests across the watch area are encouraged to closely monitor subsequent updates from the National Weather Service and local forecast providers.