115
FXUS63 KUNR 051750
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1150 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 18Z TAFS Through 18Z Friday)
Issued At 1149 AM MDT Thu Jun 5 2025

Showers and isolated thunderstorms will taper off from west to east
tonight. MVFR and local IFR conditions will slowly improve over
portions of northeastern Wyoming and far western South Dakota, but
will linger across south central South Dakota through the period.

&&

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

$$

DISCUSSION/KEY MESSAGES...Helgeson
AVIATION...Smith