Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 250521

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1121 PM MDT Sat Mar 24 2018

.DISCUSSION...(This Evening Through Saturday)
Issued at 207 PM MDT Sat Mar 24 2018

Water vapor shows large scale trof over the western CONUS with SW
flow aloft into the Northern Plains. At the surface, broad SE flow
covers the region with strong high north of the Great Lakes and
lee trof east of the Rockies. Low clouds have been tough to erode
over the SD plains this afternoon given the strong/moist SE
boundary layer flow.

Short wave will rotate through the Northern Plains tonight and
spread scattered light rain/snow showers across the region.
Thermal profiles towards central SD suggest more of a freezing
rain/drizzle threat with some light icing possible late tonight
and early Sunday before short wave ejects further east.

A brief period of dry weather expected behind the departing wave,
with temps rising into the 40s/50s Sunday afternoon, before an
even stronger wave approaches late Sunday.

This strong northern stream wave is expected to close off at 700mb
Sunday night into Monday as it crosses Northeast WY and Northwest
SD, and most model solutions support this track. Strong region of
frontogenesis along with some instability will likely lead to a
band of heavy snow near/north of the 700mb low track, especially
across northern Campbell and Crook counties where up to a foot of
heavy wet snow is possible. The band of heavy wet snow (with
slightly lesser amounts) will possibly extend through the
northern Black Hills and Northwest SD as well. Current Winter
Storm Watches look good at this time. Snow amounts expected to be
less south/east of the Black Hills, but more light icing possible
due to freezing rain across south central SD late Sunday
night/early Monday. System pulls out by Monday night.

Broad NW flow pattern expected through the end of next week, with
periodic chances for rain/snow and temps near or below average.


.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1121 PM MDT Sat Mar 24 2018

(For the 00Z TAFS Through 00Z Sunday Evening)
Issued At 526 PM MDT Sat Mar 24 2018

MVFR/IFR ceilings will continue through much of the night across
portions of northwest into south central South Dakota. MVFR/IFR
ceilings expected to develop across portions of northeast Wyoming
and western South Dakota overnight. MVFR/IFR ceilings will
persist into Sunday afternoon. Some light precipitation will occur overnight,
with rain/snow over northeast Wyoming western South Dakota. Some
freezing rain/drizzle possible over south central South Dakota.


SD...Winter Storm Watch from Sunday evening through Monday afternoon
     for SDZ001-012-024-025-028-072.

WY...Winter Storm Watch from Sunday evening through Monday afternoon
     for WYZ054>057-071.



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