496
FXUS63 KUNR 131857
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1257 PM MDT Mon May 13 2024

.KEY MESSAGES...

-Unsettled this week with periodic chances for showers and
 thunderstorms, best chances late tonight through Wednesday
 morning.

-Smoke from Canadian forest fires may linger into Tuesday morning
 before slowly shifting southeast, although it will likely return
 later in the week.

&&

.DISCUSSION...(This Evening Through Monday)
Issued at 1253 PM MDT Mon May 13 2024

Water vapor shows upper ridge extending from the Desert SW
northeastward through the Central Rockies into the Northern
Plains. Upstream trof extends from the Pac NW into the Northern
Rockies. At the surface, broad low is moving off the Northern
Rocky Mountain front, with southeast flow and steep lapse rates
resulting in quite a bit of cumulus development over the Black
Hills. Canadian wildfire smoke covers much of the Northern
Plains, with some vsby reduction across western SD. This smoke may
linger tonight into Tuesday before shifting east.

Northwestern CONUS trof will track eastward the next few days,
with increasing chances for showers/thunderstorms into Wednesday.
The initial short wave arrives later this afternoon and tonight,
with increasing theta-e advection resulting in a few
showers/storms through the night in our western zones. A better
chance for showers/storms arrives Tuesday morning with the arrival
of a stronger wave, with the better lift across our northern
2/3rds of zones. The main upper trof then moves through Tuesday
night into Wednesday morning, with the main lift over our southern
1/2 of zones. Given the lack of Gulf moisture getting pulled into
the trof, widespread heavy rains not expected, although most
areas will receive some precipitation over the next few days. The
severe threat remains low.

Chances for precipitation will decrease a bit for Thursday/Friday,
although northwest flow along with embedded waves will bring some
showers/storms at times. After cooling temps into mid week, temps
will rebound again for late in the week.

Next trof looks to move through the Northern Tier over the weekend
for more unsettled weather and cooling temps.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1008 AM MDT Mon May 13 2024

Wildfire smoke filtering into the region may cause periods of MVFR
visibilities early this afternoon, mainly across western to
central South Dakota. Conditions will gradually improve after
20-21z.

Isolated to scattered thunderstorms will develop this afternoon
and push eastward across the area tonight. Lower flight conditions
and erratic and gusty winds are possible near any storms.
Otherwise, VFR conditions are expected through the TAF period.

&&

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

$$

DISCUSSION/KEY MESSAGES...Johnson
AVIATION...Wong