666
FXUS63 KUNR 031935
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
135 PM MDT Sun Aug 3 2025

.KEY MESSAGES...

- Potential for another round of Black Hills thunderstorms Monday
  with nocturnal thunderstorms Monday night.

- Dry and warmer for the rest of the week, with hottest day being
  Thursday.

- Cold front will move through Friday, resulting in cooler
  temperatures for next weekend.


&&

.DISCUSSION...(This Evening Through Sunday)
Issued at 122 PM MDT Sun Aug 3 2025

500hpa trough is currently exiting the eastern part of of SD with
flat rockies ridge trying to amplify to our west. At the surface,
weak low pressure is located across south central SD with a
southward dragging warm front and a trailing surface trough. Big
difference in surface dwpts from west (mid 40s) to east (mid 60s).


The first thing to ponder is how long into the evening and
overnight hours will expected BH storm activity linger? While
there is some 700hpa theta-e forcing that remains overnight, with
"blah" shear profiles and ensembles showing mean layer CAPE
generally 1000 J/kg or less during peak heating, believe that most
convection will be diurnal in nature and not stay too much past
sunset.

Next potential round of storms then shows up Monday night into
Tuesday.There is pretty good agreement on 30-50kt 850hpa jet
setting up along the SD/NE border as next round of 500hpa impulses
round the top of the ridge and move into the region. Ensembles
are showing 75th percentile comp reflectivities across the
southern counties from 30 to 40 dBz with probabilities of seeing
0.10/hour rainfall at 30%. Also of note was that the ensembles
are now picking up on the probabilities of northern BH convection,
with mean CAPE values AOA 1500 J/KG and shear values AOA 40kts.
Will need to account for this as well, especially with the rally
in full swing. Have opted to considerably up the pops for the
northern Black Hills to account for the storms Monday afternoon.

After this, ridge continues to build into the region with 850hpa
temps responding as well. By Thursday much of the western half of
the CWA is 30 degrees C or higher, so expect some possible triple
digit heat on the plains. This will be ahead of the cold front
that will swing through the region Thursday night into Friday,
dropping 850hpa temps by a minimum of 10 degrees and setting up
next weekend to cool compared to seasonable norms. Expect some TS
to develop along and ahead of the front as well.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Monday)
Issued At 1115 AM MDT Sun Aug 3 2025

Storms are expected to develop over the central and southern Black
Hills in the 03/19Z to 04/00Z time frame. Local MVFR cigs/vsbys
are psbl with the storms, along with gusty winds and small hail.
Otherwise VFR conditions are expected through the valid fcst
period.

&&

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

$$

DISCUSSION/KEY MESSAGES...Hintz
AVIATION...Hintz