Area Forecast Discussion
Issued by NWS Rapid City, SD
FXUS63 KUNR 261732
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1132 AM MDT FRI AUG 26 2016
Issued at 918 AM MDT Fri Aug 26 2016
Current surface analysis shows low pressure over eastern CO, with
trough stretching northward across eastern WY into MT. Upper level
analysis shows broad trof across the Rockies and high plains. KUDX
radar now shows band of showers from north central SD into
portions of southwest and south central SD, with isolated activity
further west across portions of western SD into southeast MT.
Skies have mostly cleared out for the time being across northeast
WY and portions of far western SD behind exiting band of rain.
Temps are in the 50s with light winds in most areas.
Have updated to adjust pops and cloud cover for current trends
through the rest of the morning. Will keep general chance pops
across most of the area this afternoon as temps warm and
atmosphere becomes more unstable. The highest instability this
afternoon is expected to be across the Black Hills area and
surrounding plains. This is where a few strong to severe storms
are possible. Highs will range from the 60s over the Black Hills
to the mid 70s over portions of southwest and south central SD.
Temps may need to be adjusted a bit later today, depending on
cloud and pcpn trends.
.SHORT TERM...(Today Through Saturday Night)
Issued at 333 AM MDT Fri Aug 26 2016
Water vapor imagery shows an upper trough across the wrn CONUS with
SW flow ahead of the trough extending from the cntrl Rockies to the
Dakotas and upper Midwest. A shortwave is crossing the area is
currently pushing into the CWA. KUDX radar shows showers and storms
associated with this wave across the BH area into the I-90 corridor
toward cntrl SD. These showers will continue E/NE early this morning
as the wave continues to push across the area...exiting the ern CWA
border by 18z except continuing through scntrl SD through the aftn.
The main trough axis will cross WY today and move into the CWA late
this aftn/evng. Additional storms are expected to develop ahead of
this approaching wave during the aftn hours across ne WY into the
BH. Models continue to show decent bulk shear...and marginal
instability of 500-1000 J/KG. Should be enough to be produce some
strong to severe storms...but atmosphere still seems to be lacking
for a more widespread severe event. Cloud cover will limit highs to
the upper 60s to upper 70s today. After tonight`s precip pushes east
of the CWA...drier and warmer air will move into the region for
Saturday. Clouds will decrease from west to east becoming mostly
sunny by the aftn. Highs will reach the upper 70s to mid 80s across
the plains...and 70s across the BH. Mostly clear skies and lows in
the 50s are expected Sat night.
.LONG TERM...(Sunday Through Thursday)
Issued at 333 AM MDT Fri Aug 26 2016
An upper level ridge of high pressure will quickly rebuild across
the central and western US through the long term period. This will
bring dry conditions and warm temperatures. High temperatures
Sunday through Friday will be above average, with highs in the 80s
and 90s. As the holiday weekend approaches, the chance for
thunderstorms will also increase, as well as the threat for severe
This type of weather pattern may lead to an increased fire risk
early next week, due to low minimum relative humidity values, poor
overnight recovery, warm temperatures, and gusty winds; especially
across northeastern Wyoming.
.AVIATION...(For the 18Z TAFS Through 18Z Saturday)
Issued At 1129 AM MDT Fri Aug 26 2016
Scattered showers with isolated thunderstorms currently across
portions of Western South Dakota. MVFR/IFR cigs still persist
across portions of Western South Dakota and extreme Northeast
Wyoming. The MVFR/IFR cigs will be slow to dissipate and expect
them to last the majority of the afternoon across Western South
Dakota. Scattered showers and thunderstorms will redevelop this
afternoon across Northeast Wyoming and Southeast Montana before
moving into Western South Dakota. Could see brief MVFR cigs/vis
with some of the stronger storms. Expect VFR cigs/vis after storms
push east of the region overnight.