465
FXUS63 KUNR 160518
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1118 PM MDT Mon Jul 15 2024

.KEY MESSAGES...

-Near average temperatures, with chances for storms most days

-A few stronger to severe storms possible this afternoon and
 evening

&&

.DISCUSSION...(This Evening Through Monday)
Issued at 133 PM MDT Mon Jul 15 2024

Latest analysis shows an upper ridge over the western
CONUS and Canadian Rockies. An upper low is located over Hudson
Bay with a trough swinging southward across Manitoba/Saskatchewan,
leading 50-70kt 300mb westerly flow across the region this
afternoon. A surface high is dropping southward from the Canadian
prairie provinces into eastern MT and ND this afternoon with a
surface trough to the east of the Rockies. Surface dewpoints are
mainly in the 50s, with some 30-40F readings over northeastern
Wyoming and in the upper 60s over parts of south central SD.
SBCAPE has risen to 500 (NE WY) to 2000 (south central SD) J/kg
this afternoon. A band of 1000+ J/kg extends along the eastern
slopes of the Black Hills into southwestern SD which coincides
with a region of 40+kts 0-6km Bulk Shear. Lift associated with a
70+kt jet streak crossing the area is expected to trigger
thunderstorm development over northeastern Wyoming and the Black
Hills into southwestern South Dakota during the late aftn/early
evening. Shear profiles indicate that a few strong to severe
storms are possible.

That convection will spread eastward tonight into south-central
SD. Another band of storms may dive southeastward out of North
Dakota into parts of northwestern and north central SD later
tonight.

Additional storms are possible on Tuesday afternoon/evening with a
stronger short wave trough crossing the region and steep lapse
rates in place with northwesterly flow aloft. Tuesday highs will
be similar, or a few degrees cooler, than today. Slightly drier
conditions are expected Wednesday with more subsidence behind the
Tuesday short wave, with a better focus around and south of the
Black Hills.

Next strong short wave trough looks to move through Thursday
night/early Friday, with temperatures rebounding a few degrees
late week as upper ridge amplifies over the Northern Rockies.
Better focus for storms may shift a bit east over the weekend as
upper ridge attempts to build over the Northern Plains.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Tuesday Night)
Issued At 1117 PM MDT Mon Jul 15 2024

VFR conditions are expected through the forecast period.
Isolated to scattered showers and thunderstorms are expected
overnight, mainly in south central and northwestern SD. Transient
MVFR conditions are possible near storms.

&&

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

$$

DISCUSSION/KEY MESSAGES...10
AVIATION...Dye