Orographic Thunderstorms and Downbursts over Southeastern Wyoming

 Convective Initiation (1900 UTC)

The afternoon of 1 June 2026 has been convectively productive over and east of the Rocky Mountain Front Range of Wyoming and Colorado. The 1900 UTC composite satellite image in Figure 1 below captures the early afternoon development of a complex of strong, orographically-forced and high-based thunderstorms. These cells initially fired over the Rocky Mountain Front Range of southeastern Wyoming. As the system advected east-northeastward, satellite and MRMS data indicated rapid storm intensification, characterized by sharply cooling, ice-phase cloud tops and a significant surge in lightning flash rates. 

Figure 1: Composite SZA cloud phase distinction, MRMS reflectivity, and LightningCast probability product image at 1900 UTC 1 June 2026.

Linear Organization & Downburst Signatures (2006 UTC)

By 2006 UTC, the convection underwent a clear structural evolution into a downburst-producing thunderstorm system. The previously disorganized multicell clusters organized into a short-segment linear complex. Key Feature: The satellite presentation highlights a prominent rear-flank dry-air notch, which is a classic morphological signature of severe downburst potential as mid-level dry air is entrained into the storm's downdraft. Surface Observation: Validating this remote sensing presentation, a severe 52-knot downburst wind gust was recorded at the surface in Bordeaux, WY, at 1958 UTC, just minutes before this satellite scan.

Figure 2. Composite SZA cloud phase distinction, MRMS reflectivity, and LightningCast probability product image at 2006 UTC 1 June 2026.

Figure 3. Comparison between the GOES-19 (G19) sounding retrieval and the Rapid Refresh (RAP) model sounding at 1800 UTC 1 June 2026.

Thermodynamic Environment: Cheyenne Soundings (1800 UTC)

To understand the atmospheric mechanics driving these downbursts, we can analyze the 1800 UTC thermodynamic environment over Cheyenne, WY in Figures 3 and 4. A comparison between the GOES-19 (G19) sounding retrieval and the Rapid Refresh (RAP) model sounding reveals a prominent "hourglass-inverted-V" profile in the lower and mid-troposphere—a textbook thermodynamic setup for evaporatively cooled, severe convective wind gusts.

The associated Wind Gust Potential (WGP) derived from these profiles showed values ranging from 39.2 knots (G19) to 44.5 knots (RAP), which closely aligns with the observed severe gusts in the region.

Regional Corroboration: Denver ACARS Profile (1647 UTC)

Further corroborating the regional environmental setup is an ACARS vertical sounding profile retrieved at 1647 UTC from Denver, CO  (Denver International Airport). When compared to the Cheyenne RAP model sounding, the Denver ACARS data demonstrates excellent structural agreement across the Front Range boundary layer. Specifically, the profile highlights highly favorable wet-bulb zero heights and substantial Downdraft CAPE (DCAPE), confirming a widespread optimal thermodynamic environment for the robust downburst generation observed throughout the afternoon.

Figure 4. Comparison between the Denver, CO ACARS sounding profile at 1647 UTC and the Cheyenne, WY Rapid Refresh (RAP) model sounding at 1800 UTC 1 June 2026.

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