Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 141846

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1146 AM MST Sat Jan 14 2017

Issued at 1143 AM MST Sat Jan 14 2017

Have already raised highs a couple times this mrng, especially in
the eastern slopes of the Blkhls as temps have risen quickly in
those areas due to downslope flow. The arctic air that remains
settled in lower areas of the nwrn SD plains continues to have a
hard time mixing out due to the light winds in that area, and the
forecast highs may be too optimitic so will closely monitor.


.SHORT TERM...(Today Through Sunday Night)
Issued at 219 AM MST Sat Jan 14 2017

09z surface analysis had weak high over the Dakotas with mainly
clear skies and light winds.

Today through Sunday afternoon, surface high moves into the Great
Lakes as lee trough moves slowly east as a weak warm front. Weak
warm air advection will continue as arctic air erodes and shifts
east. Snow cover will play havoc with temperatures on the plains.
Probabilistic guidance suggests some fog is possible tonight, but
looking like deposition at this point and will leave out of forecast.

Sunday night, upper low over the southwest will eject into the
southern plains with precipitation shield reaching north into south
central SD. Given thermal profiles, wintry mix possible per NAM but
both ECMWF/GFS keep majority of inclement weather east of the CWA.

.LONG TERM...(Monday Through Friday)
Issued at 219 AM MST Sat Jan 14 2017

Quiet weather is expected through the first half of the work
week. The storm system will cross the southern to central plains
through Monday. Snow or freezing rain will transition to all snow
by early Monday morning across south central SD. Precip will end
in the morning or at the latest early afternoon. Little to no snow
accumulation is expected. A shortwave is progged to cross the
Dakotas Monday which will bring breezy northwest winds to the SD
plains. Low amplitude ridging then sets up cross the region
through the middle of the week with warmer temps. Highs Tuesday
will reach the 30s to low 40s...perhaps upper 40s to low 50s
across the northern and eastern downsloping foothills. Temps about
5-10 degrees warmer are expected Wednesday and Thursday. Cooler
and wetter weather is expected for the end of the week as a large
upper trough pushes into the western CONUS.


.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 1012 AM MST Sat Jan 14 2017

VFR conditions and light winds expected through Sunday




SHORT TERM...Helgeson
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