Area Forecast Discussion

KEY MESSAGES

- Near critical fire weather conditions Friday across portions of northeastern WY/southern SD - Unsettled weather through the weekend courtesy of a series of fronts with cool temperatures for the weekend

DISCUSSION

(This Evening Through Thursday) Issued at 103 PM MDT Thu Jun 11 2026

18z surface analysis had cold front slipping across western SD with gusty northwest winds (25-35g45 mph). Gradient relaxes for the rest of the afternoon, so suspect Wind Advisory will end early. Steep low-level lapse rates per 18z KUNR/KBIS sounding supporting extensive CU field over the CWA along with popcorn showers perking up on regional radar loop. Sliver of buoyancy may support a few lightning strikes during peak insolation. Water vapour loop had mean upper trough over central Canada with a parade of disturbances under northwest flow extending into western Canada. These disturbances are the main forecast concern.

Tonight, transient weak high will end precipitation with cool overnight lows. Tonight into Friday, shortwave trough swings into the northern Rockies with weak flat shortwave ridging nudging low level thermal ridge into the CWA. Friday looks nice with relatively light winds and warm temperatures. Friday night into Saturday, aforementioned shortwave trough slides east/southeast around Canadian upper trough. Moderate band of 800-600mb frontogenesis develops over western half of CWA, tapping into limited moisture. Result will be band of QPF with latest ensemble trends increasing amounts over northeastern WY. Just like winter, where band eventually sets up will determine who has a dreary/wet day vs just cool/moist. Cooler temperatures persist through Sunday.

Looking ahead to next week, most guidance suggests expansion of thermal ridge into the northern plains given upper flow eventually rotates from the northwest to west/southwest. Confidence medium on how quickly temperatures rise given a series weak fronts crossing the region. But, general trend is warmer/drier.

AVIATION

(For the 00Z TAFS Through 00Z Friday Evening) Issued At 519 PM MDT Thu Jun 11 2026

VFR conditions are expected through the TAF period.

Gusty northwest winds will continue to diminish over the South Dakota plains this evening. Breezy northwest winds (~25kt gusts) will return late Friday morning into the afternoon.

FIRE WEATHER

Issued At 103 PM MDT Thu Jun 11 2026

Near critical fire weather conditions expected Friday across portions of northeastern WY/southern SD as minimum relative humidity drops into the teens. Winds will be relatively light with a few gusts reaching 15-25 mph coincident with drier air. Will forgo headlines given HREF joint probabilities of RH<20%/wind gusts >25mph is very low.

UNR WATCHES / WARNINGS / ADVISORIES

SD...None. WY...None.