841
FXUS63 KUNR 091929
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
129 PM MDT Sun Jun 9 2024

.KEY MESSAGES...

- Marginal risk for strong to severe storms across northeastern
  WY and the Black Hills this afternoon and evening

- Better chances for severe weather on Monday as a stronger
  wave moves through the region

- Near to above average temperatures with near daily chances
  for showers and storms through the end of the week.

&&

.DISCUSSION...(This Evening Through Sunday)
Issued at 127 PM MDT Sun Jun 9 2024

Upper level analysis has an area of low pressure over Alberta and a
long wave trough extending down the west coast, as a ridge extends
along the western side of the Rockies. Water vapor imagery shows a
weak wave over southern Montana and Wyoming rounding the ridge, with
a much stronger wave associated with the West Coast trough. At the
surface, high pressure is centered over the Great Plains, with a
stationary boundary extending from eastern Idaho, into Wyoming and
western Colorado, as a lee trough is developing in Wyoming and
Colorado. Temperatures are currently in the lower 60s in the Black
Hills with lower to mid 70s on the plains. Dewpoints are rising
across northeast Wyoming and the Black Hills into the mid 50s.

As the Wyoming/Montana shortwave passes through the region later
today and tonight, there will be chances for showers and storms. ML
CAPE of 500-1000 J/kg and 0-6 bulk shear around 45kt should be
sufficient for isolated strong to severe storms. Drier air in the
mid to upper levels along with weak forcing due to the wave
timing, will limit stronger storms.

On Monday, the upper trough will cross the Rockies and move into the
Northern Plains. Strong southerly flow will bring 60 degree
dewpoints and warm temperatures into the region. Strong upper level
winds will provide decent shear (30-40 kt of 0-6 km bulk shear) and
ML CAPE should be 1000-2500 J/kg by mid afternoon. These factors
will create a scattered strong to severe storms Monday afternoon and
evening. The main threats from the storms will be damaging wind
gusts, and large hail. Additionally, PW values of 1-1.2" which are
150-175% of normal for this time of year, will allow for heavy rain
with the stronger storms.

After the trough passes Monday night, the upper flow becomes more
zonal for the rest of the week. Weak impulses moving through the
flow will bring near daily chances showers and thunderstorms.
Temperatures will remain above average.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Monday)
Issued At 1039 AM MDT Sun Jun 9 2024

Scattered showers/storms will continue to move across portions of
the CWA this afternoon. This evening, another round of storms is
expected to move into northeastern WY, some of which could be
strong to severe. These showers/storms will push into western SD
overnight. MVFR conditions and gusty winds will be possible in any
storms. Breezy southeasterly winds will continue into Monday
morning, and then begin to switch to the northwest late morning
as a surface trough moves through.

&&

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

$$

DISCUSSION/KEY MESSAGES...MLS
AVIATION...Pojorlie