181
FXUS63 KUNR 090425
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1025 PM MDT Sat Jun 8 2024

.KEY MESSAGES...

- A storm or two could develop over northeastern WY/southwestern
  SD this evening, with a non-zero chance of becoming severe

- There is a marginal risk of severe storms Sunday, especially
  across northeastern WY

- Best chance for severe weather arrives Monday as a stronger wave
moves through.

&&

.DISCUSSION...(This Evening Through Saturday)
Issued at 205 PM MDT Sat Jun 8 2024

Upper flow over the northern plains is nearly zonal,
between a low across Alberta/Saskatchewan and weak ridging over the
west coast. Water vapor shows a weak shortwave trough pushing
through Idaho. Morning showers have dissipated, and skies are
becoming less cloudy. Surface high pressure sits over SD, resulting
in fairly light southeasterly winds across the CWA. Temperatures are
warming into the 60s and lower 70s.

Today`s southeasterly winds over northeastern WY/southwestern SD
will result in some weak buoyancy development this afternoon,
although the best CAPE will be to our south. As the ID shortwave
pushes through WY into NE, thunderstorms are expected to develop.
Shear could support a few strong to severe storms, but expecting
most of the activity to stay to our south.

Lingering moisture and light upslope winds could produce some patchy
fog over parts of northeastern WY, the Black Hills, and SW SD late
tonight into Sunday morning.

Upper ridging will build over the Rockies on Sunday. Slightly
stronger southeasterly surface winds will contribute to warmer temps
and better buoyancy over northeastern WY and the Black Hills.
Another weak shortwave moving over the ridge is expected to
approach our area Sunday evening, which could spark another round
of storms across northeastern WY. Before then, storms could
develop over the Black Hills Sunday afternoon. With 0-6 km shear
around 40 kts, strong to severe storms cannot be ruled out. SPC
has recently placed northeastern WY in a marginal risk.

The Canadian low will push the ridge to our east Sunday night into
Monday, and the trough will slide through the northern plains. Ahead
of the trough, breezy southerly winds will allow temps to warm to
the upper 70s/lower 80s Monday, with dew points near 60, and MLCAPE
1000-1500 J/kg. Shear will be supportive of severe thunderstorms,
especially as the surface trough moves through. And with PWATs 175-
200% of normal, heavy rain is expected.

Somewhat zonal flow develops after the trough shifts east.
Occasional shortwaves and typical June warm/moist conditions will
produce storms at times through the end of next week.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1022 PM MDT Sat Jun 8 2024

Patchy fog still looks like a possibility closer between 10z and
13z this morning across sections of NE Wyoming and the Black
Hills...with MVFR cigs/vsbys associated with the fog. Scattered
showers/thundershowers are possible after 10/00z mainly across
northeast WY with the approach of another upper air disturbance.

&&

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

$$

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