000
FXUS63 KUNR 230934
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
334 AM MDT Tue Apr 23 2024

.KEY MESSAGES...

- Warm, dry, and occasionally breezy weather continues through
  Wednesday

- Unsettled weather returns late this week. Chances for showers
  and thunderstorms returning by Thursday and continuing into the
  weekend.

&&

.DISCUSSION...(Today Through Monday)
Issued at 333 AM MDT Tue Apr 23 2024

500mb analysis depicts positively tilted shortwave skirting past
the region to the northeast with a 100kt jet streak directly
overhead at 300 mb. At the sfc, a sfc low sits over the Great
Lakes region with high pressure centered over the Canadian
Rockies. This has allowed a pressure gradient to set up across the
region which has resulted in some breezy west-northwest winds,
especially over northwestern SD. However, these winds aren`t much
to write home about, generally 10 to 15 mph gusting to 20 to 25
mph at times. Skies over the region are mostly clear with
temperatures largely in the 30s to low 40s.

Our marginally breezy conditions will continue into the morning
hours, especially towards central SD where 850 mb winds of 30kts
may mix down to the sfc after sunrise. South central SD could see
some gusts 30 to 40 mph in the morning hours with winds
diminishing in the afternoon as the shortwave moves out of the
region.

Upper level ridging builds into the region by Wednesday with
vigorous return flow advecting warmer temperatures into the
region. LLJ will form over western SD Tuesday night into early
Wednesday, leading to a breezy Wednesday over much of the western
SD plains. South central SD could see some low end advsy level
gusts Wednesday afternoon. In addition, RHs over northeastern WY
will plummet into the mid-teens. However, winds over northeastern
WY will be fairly light which will preclude any fire wx concerns
at this time.

Upper low will swing through the four corners region late
Wednesday into Thursday with lee cyclone developing over the
central plains late Thursday evening. This will bring us our next
chances for showers and storms. NAM depicts 1000 J/kg CAPE over
the region Thursday afternoon, though shear is rather meager and
may preclude any widespread severe threat at this time. Rain
chances continue through Friday as the sfc low crosses the region.
As of now, it looks like south central into central SD will get
the bulk of the QPF with GEPS/ENS having the highest probs
(40-60%) of total precip accumulation of 1+" over south central SD
by Saturday afternoon.

Another shortwave and lee cyclone will follow right on the heels
of the first system, impacting the region late Saturday and
continuing our rain chances through the weekend. There`s a little
more uncertainty with the track of this system (and thus
uncertainty about how much precip we may get out of it) though
recent deterministic GFS runs have kept the bulk of the QPF over
south central SD and the most recent ECMWF run has the system
tracking further south and east and missing the CWA all together.
Either way, we`re on track for an unsettled and dreary weekend.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Tuesday Night)
Issued At 951 PM MDT Mon Apr 22 2024

VFR conditions will continue through the TAF period. Northwest
winds will become windy toward central South Dakota from 13Z-18Z
on Tuesday morning.

&&

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

$$

DISCUSSION/KEY MESSAGES...Wong
AVIATION...10