Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 161041

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
341 AM MST Sat Dec 16 2017

.DISCUSSION...(Today Through Friday)
Issued at 340 AM MST Sat Dec 16 2017

Northwest upper flow continues across the northern plains...but is
becoming more westerly this morning as an upper trough crosses the
western CONUS. Forcing ahead of this wave will result in snow
developing across Wyoming over the next few hours. This snow will
develop eastward into northeast Wyoming this morning...and into the
Black Hills late this morning into the afternoon hours. Models are
showing generally 1 to 3 inches of snow across these areas...with
the maximum of 4 inches across southern Campbell. Generally 2 or 3
inches of snow...possibly up to 4 expected across the
Black Hills, but this will be more spread out over 18 hours or
so. Not planning on expanding the current advisory. Aside from
some lingering snow showers, drier weather is expected Sunday as
the main trough axis crosses the CWA. Warm air advection will
develop with highs reaching the 40s to mid 50s by Monday and
continuing through Wednesday. A cold front will cross the region
sometime late Wednesday into Wednesday night bringing colder air
to the area. This system will also bring good chances of snow to a
wide area...though QPF amounts won`t be very high. At this time
it looks like 1 to 3 inches of snow is what most areas will
receive. Cooler than average temperatures are expected to continue
through the rest of the week.


.AVIATION...(For the 06Z TAFS Through 06Z Saturday Night)
Issued At 1016 PM MST Fri Dec 15 2017

VFR conditions expected through 10z as mid/high clouds
lower/thicken ahead of an approaching storm system. Conditions
will rapidly deteriorate after 10z across northeast WY and then
spread into western SD by 15z with IFR conditions due to ST/SN -
these conditions will persist through Saturday evening. Across
central SD, mainly VFR conditions expected through 15z Saturday,
transitioning to areas MVFR CIGS with -RASN possible through
Saturday evening.


WY...Winter Weather Advisory until midnight MST tonight for WYZ055.



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