Soundings Capture Unstable Atmosphere over Northeastern South Dakota

1. Satellite Evolution and Pre-Frontal Forcing (2030 UTC)

The afternoon of June 3, 2026, presents a classic setup for convective development across northeastern South Dakota.

Surface Features: A cold front moving eastward, combined with an outflow boundary from a preceding Mesoscale Convective System (MCS), is serving as the primary surface focus for thunderstorm initiation.

Pre-frontal Monitoring: The 2030 UTC composite satellite image captures an area of concern for downburst winds, particularly near Aberdeen, SD.

Cloud Phase Distinction: At this time, the GOES-19 SZA Day Cloud Phase Distinction product in Figure 1 below highlights pre-frontal cumulus development as distinct, blue-shaded "Cu streets," indicating the initial vertical growth of liquid-water clouds before they transition to ice-phase convection. 

Figure 1: Composite SZA cloud phase distinction, MRMS reflectivity, and LightningCast probability product image at 2030 UTC 3 June 2026.

2. Thermodynamic Analysis: The Miller Type 1 Profile (1800 UTC)

Sounding data from 1800 UTC in Figure 2 reveals a volatile environment characterized by a classic severe weather profile.

Sounding Structure: A comparison between the GOES-19 sounding retrieval and the Aberdeen, SD (KABR) radiosonde observation shows a prominent "narrow hourglass" structure.

The "Loaded Gun": This signature closely resembles a Miller Type 1 profile—often referred to as a "loaded gun" sounding—where a moist boundary layer is capped by a warm, dry layer (capping inversion) and steep lapse rates aloft.

Potential Energy: The environment features large CAPE (1694 J/kg on G19 and 2138 J/kg on RAOB) and a calculated Wind Gust Potential (WGP) of 43 to 45 knots.

Figure 2. Comparison between the GOES-19 (G19) sounding retrieval (left) and the Aberdeen, SD (ABR) RAOB sounding at 1800 UTC 3 June 2026 (right).

Figure 3. Comparison between the 1900 UTC NOAA-21 NUCAPS sounding retrieval 40 km NW of Aberdeen, SD (left) and the Aberdeen (ABR) RAOB sounding at 1800 UTC 3 June 2026 (right).

3. Regional Validation: NUCAPS vs. KABR RAOB (1900 UTC)

The regional thermodynamic environment is further validated by satellite-derived sounding retrievals.

Profile Consistency: The 1900 UTC NOAA-21 NUCAPS sounding, retrieved approximately 40 km northwest of Aberdeen, shows excellent structural agreement with the KABR radiosonde.

Downburst Ingredients: Both profiles exhibit favorable wet-bulb zero heights positioned near the 700-mb level, a key factor for maximizing evaporative cooling and subsequent downburst strength.

Forecast Outlook: Thunderstorm downburst occurrence will be most favorable during the late afternoon hours as the eastward-advancing cold front impinges on this highly unstable air mass over the Aberdeen area.

StormRangerWX