967 
FXUS63 KUNR 281908
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
108 PM MDT Tue Mar 28 2023

.DISCUSSION...(This Evening Through Tuesday)
Issued at 1241 PM MDT Tue Mar 28 2023

Water vapor shows low near Hudson Bay with flat ridge across the
Northern Plains. Next upper low is just offshore the CA/OR coast.
At the surface, broad low covers WY with frontal boundary sinking
south across western SD as surface high builds into eastern
MT/western ND. Cirrus is streaming overhead with early afternoon
temps 20s/30s across northeast WY and northwest SD, with 40s in
southern SD closer to the frontal boundary.

For tonight, jet streak embedded within the flat upper ridge will
race across the region, with band of low-mid level frontogenesis
producing some light snow from mainly the Black Hills into south
central SD. Some minor accums possible, mainly an inch or less, 
and snow should end by Wednesday morning.

Return flow sets up on Wednesday as surface high builds into the 
Upper Midwest and frontal boundary resides over eastern WY. Breezy
southeast/south winds are expected, but temps will remain rather 
cool with highs in the 30s to lower 40s.

On Thursday, upper trof works through the western CONUS. Warm
front lifts through our area with some gusty southwest winds and
mild temps as thermal ridge peaks. Warmest temps will be
south/east of the Black Hills with highs close to 60 expected.
Could see a few showers in the west by later in the day as next
cold front sweeps in from the west.

Thursday night and Friday, upper trof works into the Plains, with
upper low eventually spinning up over northeast NE or IA by late
Friday. Widespread light snow will spread east across the area 
during this time, with the better chances for accumulating snow 
over south central SD as the upper low spins up to our southeast. 
Guidance has been quite consistent with this being a progressive 
system which will help limit overall impacts. NBM probs for 2+ 
inches is in the 40-60% range across the northern Black Hills as 
well as south central SD. NBM probs for 6+ inches are much lower 
at 20-30% for south central SD. Better chances for wind would also
be across south central SD. Still looking like advisory type 
impacts and mostly south/east of the Black Hills towards south 
central SD, but should have a better idea in the next 24-36 hours.

Transitory upper ridge will bring drier and warmer weather for at
least the first half of the weekend. Next upper low/trof moves in
late in the weekend and early next week with more impactful winter
weather possible.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 1043 AM MDT Tue Mar 28 2023

MVFR cigs over NW SD should improve to VFR this morning.
Otherwise, VFR conditions expected through most of this afternoon
into the evening hours. MVFR/IFR cigs may redevelop over the 
Black Hills overnight behind a front.

&&

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

$$

DISCUSSION...Johnson
AVIATION...Wong