453
FXUS63 KUNR 041949
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
149 PM MDT Sat May 4 2024

.KEY MESSAGES...

-Becoming windy Sunday.

-Strong storm lifts into Northern Plains Monday/Tuesday;
 Thunderstorms late Sunday/Monday, windy Tuesday/Wednesday, some
 snow for the higher Black Hills Monday night-Thurs.

&&

.DISCUSSION...(This Evening Through Saturday)
Issued at 148 PM MDT Sat May 4 2024

Deep upper low is moving onshore in the western CONUS and will
provide windy and unsettled weather for most of next week starting
Sunday night. Sfc high pressure is shifting SE as pressure falls
ensue this afternoon per the approaching massive closed upper low
in the western CONUS. Winds will begin to increase from the SE
tonight, with some accentuated flow downwind the Pine Ridge in SW
SD where a few gusts over 40 mph will be possible late tonight.
Strong western CONUS upper trough will then shift east into the
Rockies and support continued pressure falls over the region Sun.
This will force increasing SE winds, becoming quite breezy by
afternoon across the western SD plains where adv winds are
expected. Have issued a wind adv given expected sustained winds of
30 to 35 mph, with gusts over 50 possible at times in the
afternoon. Winds will taper off some most places in the evening,
but may persist/increase downwind the Pine Ridge Sunday night. Pos
theta-e adv with a weakening cap will allow for a thunderstorm or
two over NE WY in the late afternoon, with convection developing
and shifting NE across NE WY and far western SD Sunday night.
Increased chances for more widespread showers Sunday night with
the main moisture surge and WAA, although the best chances will be
across mainly NW SD. Strong storm system will then move into the
plains Monday, with the sfc trough/dryline shifting east across
southwest through scentral SD. Model trends suggest that the
severe threat will remain south and east of the FA, although gusty
winds are likely along the sfc trough which may spawn some weak
convection across scentral SD. Further west, deformation rains
will spread into the region along with gusty westerly winds. Adv
winds will be possible Monday across much of western SD, with the
bulk of wind in NW SD. However, rains may limit mixing and gust
potentials there. As the upper low stalls and then slowly migrates
east, winds, rain showers, and cool weather will persist through
Wed night, with near warning level winds Tues across NW SD as dry
slotting interacts with fast flow aloft through diurnal mixing.
Rain will change to snow in the higher elevations of the Black
Hills Monday night with some light accums possible. However, the
better chance for snow accums still looks to be Tue night into Wed
when colder air advects into the region, with snow lingering into
Thur. Things will begin to slowly warm up and dry out toward next
weekend as the upper low finally exits the region and a ridge of
high pressure builds across the western CONUS.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 1125 AM MDT Sat May 4 2024

VFR conditions are expected through the TAF period. Some low-
level wind shear may develop after 06Z Sunday, especially over the
foothills and western SD plains.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory from noon MDT /1 PM CDT/ to 11 PM MDT /midnight
     CDT/ Sunday for SDZ001-002-012>014-030>032-042>044-046-047-
     049-073-075>078.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...JC
AVIATION...Dye