600
FXUS63 KUNR 050756
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
156 AM MDT Thu Jun 5 2025

.KEY MESSAGES...

- Two shortwaves will bring shra/TS through Friday
- Warmer and drier weather this weekend into early next week
- Active southwest flow may develop for the middle of next week

&&

.DISCUSSION...(Today Through Wednesday)
Issued at 153 AM MDT Thu Jun 5 2025

07z surface analysis had trough from UT into northeastern WY,
which was a reflection of shortwave across western WY into UT per
water vapour loop. Regional radar loop shows cluster of shra/TS
over WY heading into the CWA. Main forecast concern revolves
around disposition of mean upper trough from central Canada to the
southwest CONUS.

Today/tonight, shortwave moves east/northeast across the CWA with
modest QG forcing, but well-defined 800-700mb theta-e
advection/frontogenetic forcing focused on the southern half of
the area. MUCAPE <250J/kg, which will be insufficient to fuel nice
0-6km bulk shear in place, so TS should behave. Expect cluster of
shra/TS to traverse the area today, tapering off this evening.
Further north where solar insolation may break out, another day of
popcorn convection will occur. LREF/HREF QPF amounts at least
0.50" (50-80% chance) over southern half of CWA. Much lower
further north. QPF/PoPs painted to match. Temperatures will be
near guidance, but confidence lowest where clouds/precipitation
persists most of the day.

Friday, the second shortwave swings through the northern Rockies
into the central Plains. Best forcing/0-6km bulk shear misses the
area to the southwest. 250-500J/kg mean SBCAPE will be released
across the southwest half of the CWA, particularly near the Black
Hills where terrain convergence will assist. Temperatures will be
near guidance.

Saturday/Sunday, upper ridge over the Rockies will kick upper
trough away with drier northwest flow aloft developing. Several
waves will move through with the best chance of weak convection
Saturday as a cool front crosses the CWA. Breezy/windy spots
behind the front given isallobaric forcing/lower tropospheric
forecast soundings. Temperatures will be noticeably warmer
Saturday and slightly cooler Sunday.

Upper ridge influence will hold firm into Wednesday with
temperatures 5-10F above normal. There are signs southwest flow
will develop for the second half of next week portending
increasingly active weather if moisture return is sufficient.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Thursday Night)
Issued At 942 PM MDT Wed Jun 4 2025

A few showers are still ongoing tonight over the Black Hills and
western SD, and may cause localized MVFR conditions.

Additional rain and low clouds will arrive after 08-10z Thursday
morning, building from south to north with MVFR/IFR conditions
across NE WY and western SD into the day Thursday.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...Helgeson
AVIATION...Dye