427
FXUS63 KUNR 122015
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
215 PM MDT Sat Jul 12 2025

.KEY MESSAGES...

-Dry this weekend with temps warming back up through Monday

-Marginal Risk (1/5) for severe weather over western South Dakota
 on Monday.

-Unsettled conditions return next week with a significant cool
 down mid next week

&&

.DISCUSSION...(This Evening Through Saturday)
Issued at 158 PM MDT Sat Jul 12 2025

Upper-level ridging remains anchored over the central CONUS,
supporting the mostly clear skies and dry conditions across
western South Dakota. The ridge axis will gradually shift eastward
through Sunday, allowing for increasing southwesterly flow aloft.
At the surface, high pressure over the northern Plains will drift
east, with return flow developing across the western Dakotas. This
will lead to modest moisture advection and a warming trend through
Monday.

By late Monday, a weak shortwave embedded in the southwesterly
flow may initiate some isolated convection across the Black Hills
and adjacent plains. Forecast soundings show marginal instability
(MLCAPE 500-1000 J/kg) and weak shear suggesting a low-end
thunderstorm potential. PoPs were maintained in the 20-30% range.
There is a marginal risk for severe thunderstorms for portions of
western South Dakota Monday afternoon highlighted by the Storm
Prediction Center.

A more amplified upper trough will dig into the northern Rockies
Tuesday, enhancing mid-level ascent and destabilizing the column.
Increasing PWATS (~1.2-1.4") and steepening lapse rates will
support scattered to widespread showers and thunderstorms Tuesday
afternoon and evening. Ensemble guidance suggests a 40-50% chance
of measurable precipitation across much of western SD plains.

Wednesday appears to be the most active day as the trough axis
crosses the region. Broad cyclonic flow and embedded shortwaves
will maintain widespread cloud cover and precipitation. PoPs range
from 60-70% with a higher probability of measurable rainfall.
Model consensus supports QPF totals of 0.25-0.50", with locally
higher amounts possible. Expect daily thunderstorm chances
throughout the week before things begin to dry out by next
weekend.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 114 PM MDT Sat Jul 12 2025

VFR conditions through the period.

&&

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

$$

DISCUSSION/KEY MESSAGES...Woodward
AVIATION...Dye