Area Forecast Discussion

KEY MESSAGES

- Hot on Saturday. High-based storms with strong winds are possible over portions of northeast Wyoming and far northwestern South Dakota.

- A cold front moves through Sunday with showers and thunderstorms and cooler temperatures on Monday.

UPDATE

Issued at 528 AM MDT Sat Jun 6 2026

Wind gusts were increased based on latest ensemble data and hi- res models. Issued Wind Advisory for NW SD due to enough confidence in wind gusts around 40 to 50 mph.

UPDATE Issued at 912 PM MDT Fri Jun 5 2026

No major changes with this forecast update. Main concern over the next 24 hours is the high temperature forecast for tomorrow (Saturday). Widespread highs in the mid to upper 90s across the Wyoming and South Dakota plains; can we push close to 100 in spots given the recent rains and green-up? Despite the recent precipitation, expect elevated to near-critical fire weather conditions, especially across northeastern Wyoming where RH will fall into the single digits to around 10 percent. Otherwise, overall forecast remains on track through the weekend.

DISCUSSION

(This Evening Through Friday) Issued at 1245 PM MDT Fri Jun 5 2026

Upper level analysis has mostly zonal flow over the Northern Plains with a shortwave ridge on the east side of the Rockies. At the surface high pressure is centered over the area with an area of low pressure in northeastern Washington and a trailing cold front into northern California. Visible satellite indicates a cu field over northeast Wyoming, around the Black Hills, and across southern and easter portions of the forecast area.

Mostly sunny skies will continue through the afternoon with a slight chance of a diurnally, terrain driven shower or storm this afternoon. Dewpoints are in the 50s to low 60s over the hills could produce brief heavy rain.

On Saturday it will be hot. NBM has highs in the 90s with upper 90s over northeast Wyoming and southwestern South Dakota. HREF spreads are between 90 degree and 94 degrees for KRAP whereas the NBM is much higher at 98 degrees. With all the recent rain and greenness around, it appears the NBM is running to high. Therefore, I bumped down temperatures about 5 degrees over the South Dakota Plains to fall more in line with the HREF 25-75th percentile highs. A few high-based showers and storms are possible Saturday afternoon and evening over northeast Wyoming, the Black Hills, and far northwestern South Dakota ahead of a deepening lee cyclone. Strong diurnal heating combined with height falls and steep lapse rates in the afternoon will bring the potential for afternoon showers and storms. The more favored environment is over eastern Montana and western North Dakota, but ample shear within the forecast area could result in a few storms with strong wind gusts of 60+ mph.

A cold front moves through on Sunday and Sunday night, entering the forecast area around 12Z before exiting around 12Z Monday. Energy ahead of a shortwave trough aided by a jet streak and strong surface heating could result in some terrain driven storms. Additional storms will be possible during the evening along the surface front as the strong boundary-layer heating erodes the capping. Thus expect some isolated severe storms.

Monday will be cooler across the entire forecast area behind the cold front. Surface high pressure will slide across the CWA through the day with upper level southwest flow. Another hot day is ahead on Tuesday with prefrontal warming before a deep upper low and another cold front impact the area on Wednesday and Thursday. Overall, this pattern will result in daily chances for showers and 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.