Area Forecast Discussion
Issued by NWS Rapid City, SD

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389
FXUS63 KUNR 180933
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
233 AM MST Wed Jan 18 2017

.SHORT TERM...(Today Through Thursday Night)
Issued at 232 AM MST Wed Jan 18 2017

09z surface analysis had lee trough/warm front from eastern MT
into central NE. Downslope flow has pushed relatively mild air
across snow cover early this morning with steady/slowly rising
temperatures.

Today and tonight, weakening upper ridge remains in place with
temperatures in the 50s over the higher terrain, 40s where snow
cover is becoming patchy, and 30s over areas of entrenched snow
cover. Upper low currently over the southwest will move into the
central plains with some high clouds pushing into the CWA late.

Thursday, upper low spins northeast, replaces upper ridge, and
weakens as upper trough develops over the west. Slow increase in
clouds expected late. 00z NAM suggests a stratus deck with perhaps
some drizzle possible in the far east late, but other guidance shows
drier air. Will favor drier guidance given recent NAM boundary layer
issues with moisture from modeled snowmelt.

.LONG TERM...(Friday Through Tuesday)
Issued at 232 AM MST Wed Jan 18 2017

A west coast upper trough will move into the region towards the
end of the week and into the weekend, bringing cooler air (highs
in the 30s) and chances for light precipitation. Dry weather will
return briefly Sunday with another upper ridge, and then precip
chances increase again early next week as another trough moves
through. ECMWF and GFS both continue to show a closed low sliding
through CO/NE/KS Tuesday into Wednesday. The ECM has the more
northerly track...but both solutions have precip affecting mainly
southwest to south central SD with snow accumulations. Will have
to watch this system for any shifts toward an even more northerly
track.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Thursday Morning)
Issued At 232 AM MST Wed Jan 18 2017

VFR conditions are expected through the forecast period.

&&

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

$$

SHORT TERM...Helgeson
LONG TERM...13
AVIATION...13



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