239
FXUS63 KUNR 300442
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1042 PM MDT Sat Jun 29 2024

.KEY MESSAGES...

- Chance for isolated storms Sunday with the possibility of a
  strong to severe storm or two in northeastern WY.

- Elevated fire weather concerns over northeastern WY Sunday
  afternoon.

- Chance for storms on Monday with strong to severe storms
  possible, especially towards central SD.

- Unsettled weather will continue through the week with near daily
  chances for showers/storms.

&&

.DISCUSSION...(This Evening Through Saturday)
Issued at 216 PM MDT Sat Jun 29 2024

It`s shaping up to be a pleasant afternoon across much of the CWA
with temperatures in the mid 60s to 70s. Skies are mostly clear
across northeastern WY into southwestern SD with patchy cloud
cover over northwestern into south central SD. WV imagery depicts
broad ridging over the western US with dry air mass in place
across much of the central and northern plains. Sfc analysis
depicts large sfc high over the northern plains.

Moisture advection from a LLJ coupled with forcing from a weak
impulse will bring the potential for isolated thunderstorms across
western SD late tonight into the early morning hours. Lee trough
develops through the day Sunday with the tightening pressure
gradient over the western SD plains lending to strong southerly
winds. Gusts may approach advsy level in some spots but coverage
and duration of these gusts preclude any issuance of an advsy at
this time. Temperatures tomorrow will be much warmer than today
with highs in the upper 80s to 90s across much of the area.

Weak wave crosses the region late in the afternoon, while low
level moisture will be decent across the western SD plains thanks
to the southerly flow - drier air at the mid levels will result in
a strong cap which will limit any storm development. Better
chances for storms will be out in northeastern WY along the
dryline with a narrow corridor of 1500-2500 J/kg MUCAPE. While the
potential for storms are better in WY, they`re still not great.
Fcst soundings over northeastern WY still depict dry air at the
mid levels with very dry air at the sfc. If anything does get
going, 0-6 km shear values of 40-50kt will be supportive of strong
to marginally severe storms. Convection will make its way into
western SD by the evening hours, though strength and coverage will
be limited due to aforementioned conditions.

Afternoon RHs over northeastern WY will drop into the teens to
low 20s. The very hot and dry conditions coupled with breezy
southerly flow and the potential for afternoon convection will
result in elevated fire wx concerns across portions of Campbell
and Weston Counties in northeastern WY.

Upper level trough with attendant front will cross the region
Monday, bringing chances for storms to the region once more.
Severe threat will be better Monday afternoon, especially towards
central SD where deeper moisture will be available.

Upper trough will move to the east by the midweek with quasi-
zonal flow setting up over the region. Temperatures will moderate
with highs in the 70s to 80s for most of the week. Impulses riding
along the flow will result in daily chances for showers and
storms.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1040 PM MDT Sat Jun 29 2024

Gusty southeasterly winds expand from northeastern WY overnight to
northwestern SD Sunday. Isolated/scattered showers/thunderstorms
will occur east of the Black Hills 09z-18z Sunday and then over
northeastern WY/Black Hills Sunday afternoon/early evening. Local
MVFR conditions will occur with the strongest storms. Otherwise,
VFR conditions will prevail through the period.

&&

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

$$

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