868
FXUS63 KUNR 132315
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
515 PM MDT Thu Jun 13 2024

.KEY MESSAGES...

- Chances for showers and thunderstorms increase late tonight and
  Friday, with a marginal risk for severe storms on Friday.

- A more unsettled pattern for the weekend and the first half of
  next week, with occasional chances for showers and storms.

&&

.DISCUSSION...(This Evening Through Thursday)
Issued at 240 PM MDT Thu Jun 13 2024

Current surface analysis shows a cool front from the western
Great Lakes to the central Plains, with high pressure sliding into
the northern Plains. Upper level analysis shows shortwave trough
over the upper Midwest, with weak ridging over the northern
Rockies and high pressure centered over NM. Skies are mainly sunny
with more seasonable temps this afternoon, mid 70s to mid 80s.
Winds are relatively light with high pressure moving over the
area.

Dry and pleasant weather will continue through the evening hours.
Low level southerly jet will develop and intensify over the
northern/central high plains overnight, mainly from western NE to
eastern MT, as high pressure starts to slide east of the region.
Theta-e advection will increase across these areas as well. There
will be increasing chances for showers and thunderstorms later
tonight and especially on Friday (20 to 50 percent), initially
across southern parts of northeast WY and southwest SD, then
eventually spreading across a good portion of western SD during
the day. Breezy southerly winds will bring increasing moisture and
some warmer air into the area. Highs will reach the 80s to around
90 across much of the Plains, with 70s over the higher Black
Hills. Assuming we get sufficient sunshine and warming during the
day, MLCAPE will increase to 1000 to 2000 j/kg by early afternoon
from far northeast WY to much of the western SD plains. Shear
looks to be strong enough for at least short-lived supercell
potential over the Black Hills area. Better upper level support
for more widespread storm potential may hold off until late in the
day and the evening. A marginal risk for severe storms is in
place across most of the area, especially the Black Hills area and
eastward, mostly during the PM hours. Large hail and eventually
strong wind gusts would be the primary threats from stronger
storms.

The weekend looks to be decent overall, but Sunday will be the nicer
day of the two. A large scale upper trough will move across the
Pacific NW into south central Canada over the weekend, with
southwesterly flow developing across the northern Plains. Saturday
will be very warm, ahead of an approaching cold front, with highs in
the mid 80s to lower 90s in most areas. Chances for showers and
thunderstorms will increase again in the afternoon, at least over
from far northeast WY to the Black Hills and northwest SD, as
some embedded energy passes over the region. Better chances again
may hold off until late day and evening as the front arrives over
northern/western areas. Later timing of front may limit severe
potential, but the better chances for stronger storms would mostly
likely be from far northeast WY to the Black Hills and northwest
SD. Front pushes through the area Saturday night with gusty
northwesterly winds and cooler air for Sunday. Sunday looks to be
dry as the upper trough tracks well north of the region and much
drier air pushes into northeast WY and much of western SD. Highs
will be more seasonable, mostly in the 70s and lower 80s. Another
upper level system is progged to cross the northwest US into the
northern Plains/south central Canada late in the weekend and early
next week, with chances for storms returning by later Sunday
night and Monday. The first half of next week could be fairly
stormy and cool, depending on the exact track of the system and
embedded disturbances within, which is still fairly uncertain at
this point. Highs look to only be in the 60s and 70s for the
Monday through Wednesday period. A warmer and drier pattern could
develop toward the end of the week.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Friday Evening)
Issued At 507 PM MDT Thu Jun 13 2024

Isolated showers and thunderstorms are possible mainly over
southwestern South Dakota after 06Z tonight, continuing through
Friday morning. VFR conditions are expected through the TAF
period.

&&

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

$$

DISCUSSION/KEY MESSAGES...26
AVIATION...JC