Area Forecast Discussion

KEY MESSAGES

- High-based storms capable of gusty winds are possible over northeast Wyoming, far western South Dakota, and the Black Hills through the overnight hours.

- A cold front moves slowly through the area Sunday and Sunday night, bringing showers and thunderstorms, severe storms are possible.

DISCUSSION

(This Evening Through Saturday) Issued at 110 PM MDT Sat Jun 6 2026

Upper level analysis has a shortwave ridge centered over the Eastern Dakotas with a low dropping into the Pacific Northwest. At the surface a cold front extends from northeastern Montana into southwestern Idaho, with a weak lee trof developing near the Bighorns. Visible satellite indicates a few mid level clouds ahead of the front with the lower portions of the UNR 18Z sounding showing very dry air off the surface.

For tonight, a high-based storm or two could get going over the Black Hills or northeastern Wyoming due to daytime heating and the forcing of the lee trof. Hi-res models are indicating a broken line of strong showers and storms along the trof, extending along the WY/SD border by 02Z-ish. With limited low-level moisture, the primary threat would be gusty winds.

The cold front approaches the area around 06Z tonight, reaching the SD/WY border near 12Z. From there, it is expected to stall- out. This stalled boundary will be the primary focus for convection during the afternoon and evening. Supercell development is possible with 0-6 km shear estimated to be 40-50 kts, steep lapse rates, MLCAPE of 1700 J/kg, and MUCAPE 2400 J/kg. With drier air still expected off the surface and dewpoints ranging from 35 to 55 degrees, expect LP supercells capable of producing significant hail and very strong winds. A tornado could also be possible.

Monday will be cooler behind the cold front, with highs only in the 70s and 80s. Surface high pressure will slide through the CWA, resulting in increasing southeasterly winds of 10-25 mph during the afternoon. Another hot day is ahead on Tuesday with prefrontal warming back into the 90s. Once again the NBM is probably running too, due to the greenness. A deep upper low and another cold front impact the area on Wednesday and Thursday, resulting in a chance for scattered storms.

AVIATION

(For the 18Z TAFS Through 18Z Sunday) Issued At 1123 AM MDT Sat Jun 6 2026

VFR conditions are expected through most of the forecast period. Isolated high-based thunderstorms are possible across portions of northeast Wyoming and the Black Hills where transient MVFR conditions are possible, along with gusty/erratic winds. Widespread, gusty (~30kts) south/southeasterly winds will persist into the late afternoon before weakening during evening hours.

UNR WATCHES / WARNINGS / ADVISORIES

SD...Wind Advisory until 9 PM MDT this evening for SDZ001-002-012>014- 078. Wind Advisory until 6 PM MDT this evening for SDZ031-072-073. WY...None.