914
FXUS63 KUNR 051150
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
550 AM MDT Sat Jul 5 2025

.KEY MESSAGES...

- Scattered strong to severe thunderstorms possible this
  afternoon, main concerns are large hail and damaging winds.

- Daily chances for storms will continue through at least Tuesday.

- Average to above average temperatures will persist through the
  beginning of next week.

&&

.DISCUSSION...(Today Through Friday)
Issued at 324 AM MDT Sat Jul 5 2025

Nighttime microphysics RGB shows clearing skies over northeastern
WY with mid to high cloud cover over western SD. 06Z sfc analysis
depicts cold front draped across ND into northwestern SD. Mostly
dry conditions should continue through this morning as shortwave
ridging builds into the region. Another shortwave and 40- 55kt
500mb jet approaches the region later this afternoon and evening.
Low pressure/inverted sfc trof will develop over eastern WY in the
afternoon hours with southeasterly-easterly sfc winds advecting
moist air into the region with sfc dews exceeding 50F. Corridor of
1000+ J/kg SBCAPE progged to develop across southwestern SD into
northeastern WY with deep layer shear increasing through the
afternoon as the upper level jet streak approaches. Modest
capping should limit convection for most of the area through the
afternoon, though upslope flow over the Black Hills could be
enough to overcome capping and we could see convection over the
hills as early as 18z. Chances for storms increase through the
afternoon and evening hours as the upper wave nears and upstream
convection approaches the region. In terms of severe potential,
bulk shear values of 30-40kt should be enough to support organized
convection and rotating updrafts. With any early afternoon
convection over the Black Hills, straight line hodographs favor
splitting storms and a hail threat. Later in the afternoon,
steepening low and mid level lapse rates, increasing low-level
shear, and DCAPE approaching 900+J/kg will be supportive of both
severe winds and hail. Later in the evening, after around 03z,
CAMs have been consistent in depicting MCS feature exiting MT and
entering western SD as the upper level wave crosses the region.
Main concerns with this convection would be damaging wind gusts.

Storms could develop once again Sunday afternoon as parent
shortwave and jet streak lingers over the region. Though there is
some question as to how convection Saturday evening/night will
affect conditions on Sunday and the better environment for severe
weather may be south of the CWA. Zonal upper flow will continue
through early next week with embedded shortwaves bringing periodic
chances for storms as a warm, buoyant environment remains in
place. Upper level ridge progged to build into the region by
Wednesday, which should limit severe potential and support a
warming trend.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Sunday Morning)
Issued At 542 AM MDT Sat Jul 5 2025

Low stratus and associated MVFR CIGS have developed across the
northern and eastern foothills. These clouds should lift after
15-16z. There`s a chance for TSRA to develop over the Black Hills
after 18z, storms will be capable of large hail and strong and
erratic winds. Chances for TSRA will increase across northeastern
WY into western SD later this afternoon and evening. Storms may be
strong to severe and capable of large hail and strong and erratic
winds. Chances for -SHRA/TSRA will continue through the overnight
hours.

&&

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

$$

DISCUSSION/KEY MESSAGES...Wong
AVIATION...Wong