846
FXUS63 KUNR 171040
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
440 AM MDT Fri May 17 2024

.KEY MESSAGES...

- Cold front this evening with gusty northwest winds.

- Strong to severe thunderstorms late this afternoon and evening
  across northwestern South Dakota with the main threat damaging
  wind gusts.

- Unsettled pattern continues through much of next week.

&&

.DISCUSSION...(Today Through Thursday)
Issued at 222 AM MDT Fri May 17 2024

Current surface map places low across southern Saskatchewan with
weak trough extending into central South Dakota. Subtle shortwave
is crossing the western Dakota with a few showers across
northwestern South Dakota. Current shower activity will come to an
end early this morning. Surface low deepens across Saskatchewan
this afternoon with secondary low developing around the Big Horns
into southeastern Montana. Low level thermal ridge peaks this
afternoon with breezy south-southwest winds with highs reaching
the 80s across the plains of western South Dakota. Lack of buoyancy
will initially limit thunderstorm development to Black Hills
this afternoon. Better chance of thunderstorms comes across
northwestern South Dakota late this afternoon/evening with
increasing mid level forcing and cold frontal passage. The cold front
arrives in northeastern Wyoming and northwestern South Dakota
late this afternoon and moves through the rest of western South
Dakota this evening. Overall, buoyancy/shear may be enough for a
marginally severe hail threat. The biggest severe threat will be
damaging winds with enhanced downdrafts given available DCAPE.
Post-frontal pressure rises of 4-6mb/3hr will result in a period
of gusty northwest winds. Have issued a wind advisory for the
plains of northwest/west-central South Dakota for this
evening/overnight.

Dry, cooler, and breezy conditions expected Saturday. Next
shortwave impacts the area late Sunday with a chance of showers
and thunderstorms. Upper trough lingers across the Pacific
Northwest/Northern Rockies through much of next week with a series
of impulses crossing the area. This will result in daily chances
for showers and thunderstorms.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Saturday Morning)
Issued At 440 AM MDT Fri May 17 2024

Isolated showers will continue to affect northwest South Dakota
early this morning, bringing occasional erratic and gusty winds.
Thunderstorms will develop this afternoon across far northeast
Wyoming, the Black Hills area, and northwest South Dakota. Strong
winds will be possible with these storms, along with hail and
MVFR conditions. Otherwise VFR conditions are expected through the
TAF period. A cold front will bring strong northwest winds to the
area this evening, with gusts to 45 kt possible.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory from 6 PM this evening to 3 AM MDT Saturday for
     SDZ001-002-012>014-025-026-031-032-072-073-078.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...7
AVIATION...13