000
FXUS63 KUNR 231734
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1134 AM MDT Wed Aug 23 2017

.DISCUSSION...(Today Through Tuesday)
Issued at 158 AM MDT Wed Aug 23 2017

The northern plains are situated between an upper level ridge to
the west and a trough to the east. Skies across the CWA are clear.
Surface high pressure stretches across the eastern Dakotas, with
a surface trough and stationary boundary to the west, and light
easterly winds in between. Temperatures are falling into the 50s.

Upper ridge axis will shift over the Rockies today, as a Canadian
low pressure system begins pushing into the Pacific Northwest. Warm
and mostly dry weather will continue, with highs warming near 90,
and just a slight chance of afternoon showers and thunderstorms over
the Black Hills.

Chances for showers and thunderstorms will increase Thursday and
Friday, as the ridge breaks down and a couple waves associated with
the upper level trough pass through the region and interact with the
stationary boundary. Best chance Thursday will be across the
southwestern half of the CWA, but more widespread precipitation is
possible on Friday. MLCAPE of 500-1500 J/kg may support a few
stronger storms on Thursday, but shear is weak, so severe weather
should be minimal. Instability and shear look stronger on Friday.

A stronger upper ridge will begin building over the western CONUS
Saturday. One more shortwave is expected to pass through
northwest flow and produce a few showers and thunderstorms on
Saturday, but then a few days of dry weather will begin. High
temperatures for the end of this week through the beginning of
next week will stay near seasonal averages, in the 80s.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 1132 AM MDT Wed Aug 23 2017

There is a slight chance of thunderstorms over the Black Hills
this afternoon. Otherwise, VFR conditions are expected through
the forecast period.

&&

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

$$

DISCUSSION...Pojorlie
AVIATION...15