610
FXUS63 KUNR 011118
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
518 AM MDT Sat Jun 1 2024

.KEY MESSAGES...

- Warming up this weekend with chances of showers and
  thunderstorms at times across the Black Hills and areas to the
  east. Some storms could be strong to severe over the weekend.

- Warm weather expected for much of next week with drier conditions
  mid to late week.

&&

.DISCUSSION...(Today Through Friday)
Issued at 300 AM MDT Sat Jun 1 2024

Current surface analysis shows weak high pressure over western/central
SD, with weakening front to the south and east of the region.
Upper level analysis shows low pressure still over central Canada,
with trough extending south into the northern Plains. Another
trough is located over the lower MS river valley, with ridging in
place over the Pacific NW. Skies are clear to partly cloudy in
most areas, with some showers/storms over western NE into far
southwest SD as mid level theta-e advection increases. Temps are
in the 40s and lower 50s with light winds.

Warmer air is starting to push into the region tonight as the
surface high begins to shift east of the area this morning. Highs
today will reach into the 70s across much of the area, with 60s and
lower 70s over the Black Hills. Winds will turn to the south and
southeast later this morning and afternoon, but are expected to
remain relatively light. Showers and storms will likely continue to
develop further north and east into southwest and south central SD
early this morning. Brief heavy rain and perhaps some small hail are
possible with any stronger cells. This morning activity may end up
limiting potential for additional storms later today across these
areas, but some additional development is possible this afternoon
into tonight from the Black Hills and southwest SD to south central
SD. MLCAPE values of 500 to near 1500 j/kg are progged for areas
from the Black Hills to south central SD as low level moisture
increases, highest values toward south central SD. Shear looks
favorable for supercell development if storms can develop. Large
hail would be the primary threat from stronger storms, but strong
winds are also possible. The more favorable environment looks to be
south of the forecast area, across the central high Plains.
Additional showers and storms are also possible late tonight into
early Sunday across mostly western and south central SD as low level
jet intensifies over western NE into the western Dakotas. For
Sunday, a more widespread chance for showers and storms is expected
as a cold front and stronger disturbance aloft approach the area.
Highs on Sunday will range from the lower 70s over northeast WY and
the higher Black Hills to at least the mid 80s over south central
SD. Timing of the cold front passage looks to be early enough in the
day to limit severe potential to areas mainly east of the Black
Hills and especially into central SD, where CAPE values are progged
to exceed 2000 j/kg in the afternoon ahead of the front. Strong
winds and hail would be the main threats as a line of storms could
eventually develop toward central SD later in the afternoon.

The front will generally wash out to the southeast of the area
Sunday night with a quick return to warmer temps for Monday. Another
cold front and stronger shortwave trough will swing through south
central Canada and the northern Plains later Monday into Tuesday.
This system should bring the best chances for showers and storms
from northeast WY to northwest SD. Any severe threat looks rather
low at this time. For the rest of the week, a building ridge over
the western US and a large scale trough over the eastern half of the
US will likely keep our area at least seasonably warm and mostly
dry. There is uncertainty with the temp forecast for mid to late
week, depending on whether the ridge can eventually progress
eastward into the Plains toward the end of the week.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Sunday Morning)
Issued At 515 AM MDT Sat Jun 1 2024

Isolated showers, and a few thunderstorms, will occur over parts
of southwestern and south central South Dakota until around 15Z
this morning. More isolated to scattered thunderstorms are
expected to develop this afternoon and evening. LCL MVFR
conditions are possible near any showers and thunderstorms,
otherwise VFR conditions will prevail through the forecast period.

&&

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

$$

DISCUSSION/KEY MESSAGES...26
AVIATION...10