Spearfish, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

145
FXUS63 KUNR 311642
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1042 AM MDT Sat May 31 2025

.KEY MESSAGES...

- Leftover PoPs end this morning over south-central SD
- Mild today, warm Sunday
- Upper level trough and cold front Monday continue to increase
  speed, shifting higher impacts eastward
- Unsettled weather continues next week with daily chances for
  showers and thunderstorms

&&

.DISCUSSION...(Today Through Friday)
Issued at 208 AM MDT Sat May 31 2025

08z surface analysis had cool front from eastern ND to KVTN to
southeast WY. Water vapour loop had compact upper low over central
ND with a small cluster of shra/TS ahead of it. Further west,
upper ridge was building from the West Coast into the Rockies.

Today, compact upper low shifts south/southeast pushing cool
front out of the CWA. Most guidance hints at isolated shra/TS this
morning per weak CAPE/forcing, although moisture is scant on the
west side of the upper low. Surface smoke may sneak into eastern
reaches of the CWA per HRRR guidance. NBM temperatures look okay,
but perhaps a little warm depending on how thick high-level smoke
is.

Tonight/Sunday, upper/thermal ridge build into the northern
Plains as temperatures soar well into the 80s/around 90F Sunday
afternoon which is in line with forecast soundings.

Sunday night/Monday, upper ridge breaks down as upper trough zips
across the northern Rockies into the northern Plains. Latest
ensemble guidance continues faster movement with cold front
reaching south-central SD around 18z. 1-2KJ/kg SBCAPE pools ahead
of the front, but may exit the CWA before surface-based convective
initiation occurs and better 0-6km bulk shear catches up. Day 3
slight risk has shifted eastward as a result, skimming the far
eastern borders of the CWA. Still looks like QG/frontogenetic
forcing ahead of upper trough/behind cold front will support
shra/TS Monday night, but QPF amounts have decreased except in the
far south. Chance of >0.10" 50-80% over the CWA with >0.50"
chance 50% over south-central SD. Probabilistic guidance suggests
gusty winds will occur behind the cold front given 25-35kt
800-850mb winds (NBM has 30-60% chance >40mph gusts from K2WX-
KRAP-KIEN. Temperatures will be tricky, so haven`t strayed much
leaving large temperature gradient for MaxT Monday.

The rest of next week looks unsettled as progressive west/northwest
flow slings a series of fronts through the region. Coolish to start,
but then warming toward the end of the week.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 1041 AM MDT Sat May 31 2025

VFR conditions are expected through 18Z Sunday.

&&

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

$$

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