090
FXUS63 KUNR 130446
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1046 PM MDT Sun May 12 2024

.KEY MESSAGES...

- Chances for thunderstorms late this afternoon into this evening. Severe
  weather is not anticipated.

- Smoke from wildfires will filter into the region this evening with
  chances for degraded air quality in some areas.

- Warm and unsettled conditions with near daily chances for
  showers and afternoon thunderstorms. Best chances for precip is
  Monday night through Tuesday.

&&

.DISCUSSION...(This Evening Through Sunday)
Issued at 139 PM MDT Sun May 12 2024

Upper low is centered over CO with weak cool front/sfc trof
draped across eastern into south central SD. Not much cold air is
filtering in behind the front with temperatures in the region in
the low to mid 70s. The front has been advecting some light smoke
from Canada into the FA, with some stations in central SD
reporting moderate to unhealthy AQ. A few showers and storms have
popped up over the BH over the past couple of hours. Weak
instability of 250-500 J/kg CAPE will continue to support slight
chances for thunderstorm development this afternoon, especially in
the southern BH thanks to eddy convergence due to the northerly
winds. Not anticipating any severe weather as shear is minimal
(generally 15 to 20 kts effective shear) though inverted V
profiles and DCAPE values of 800-900 J/kg are supportive of
strong, gusty winds in some of the stronger storms. CAMS hint at a
small line of convection moving southeast across the BH after
00z. Again, the environment isn`t expected to be conducive to
severe storms.

Conditions should clear out later tonight as a weak upper ridge
builds into the region. This should provide decent viewing
conditions for the northern lights (should they appear and should
the smoke not obscure the view of the sky too much) with lows in
the mid to upper 40s.

Northwest flow develops over the region early next week with
periodic disturbances creating chances for showers and afternoon
storms. The best chances for storms will be Monday night into
Tuesday as a shortwave crosses the northern plains. Better
moisture, higher CAPE of 1000-2000 J/kg, and bulk shear values of
30 to 40 kts may support a strong to severe storm or two over the
BH Monday afternoon and evening with wider spread convection
moving through late Monday night as a front crosses the region.

Mean troughing persists into midweek with continued chances for
showers and perhaps a few afternoon storms each day. Temps will
remain rather seasonable with highs in the 70s.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1043 PM MDT Sun May 12 2024

Wildfire smoke filtering into the region may cause periods of MVFR
visibilities this morning, mainly across western to central South
Dakota.

Isolated to scattered thunderstorms will redevelop Monday
afternoon and push eastward across the area Monday night. Lower
flight conditions and erratic and gusty winds are possible near
any storms. Otherwise, VFR conditions are expected through the
TAF period.

&&

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

$$

DISCUSSION/KEY MESSAGES...Wong
AVIATION...13