Area Forecast Discussion
Issued by NWS Rapid City, SD
FXUS63 KUNR 291733
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1033 AM MST Tue Nov 29 2016
Issued at 1019 AM MST Tue Nov 29 2016
Heavy upslope snow continues in the Black Hills with recent
reports of nearly 18 inches so far in a few areas...and would not
be surprised to a few amounts near 2 feet before the storm winds
down late tonight. Lighter snow amounts in the plains but strong
northwest winds creating very hazardous travel conditions. The
biggest change to the forecast was to add Tripp county to the
Winter Weather Advisory. Conditions already improving over
Campbell county and will likely be able to cancel the advisory
early. Expect conditions to improve from west to east tonight.
.SHORT TERM...(Today Through Wednesday Night)
Issued at 239 AM MST Tue Nov 29 2016
09z surface analysis had stacked low over the SD/ND/MN border.
Upper low spreading bands of -SN into the CWA early this morning
with distinct upslope/downslope/downstream convergence signatures
on KUDX WSR-88D. The disposition of this system is the main
Today and this evening, upper low moves little and weakens a bit. A
couple of impulses will rotate around it maintaining bands of -SN
much of the day under weakening TROWAL over the Dakotas. Guidance
continues to advertise well-defined upslope snow event for the
northern Black Hills, adjacent foothills, and parts of northeast WY.
Additional snow of 4-8 inches+ possible over the favored higher
terrain. Could see an area of moderate snow downstream over parts of
Oglala Lakota into Bennett and Jackson counties. New snow amounts on
the plains will be highly variable. Areas of strong winds will
continue as surface trough moves from ND into western SD this
morning. Have upgraded Rapid City area to High Wind warning as a
result. Winter headlines still look good given combination of snow
and blowing snow through this evening, but will need to watch
downstream convergence areas for possible upgrade.
Overnight into Wednesday, upper low weakens and starts moving away.
Gradient will slacken as well as areas of -SN with upslope tailing
off significantly. A bit of accumulation possible Wednesday over
central SD as last gasp of upward vertical motion from system moves
Wednesday night, a chilly night in store with wide variability
in temperatures depending on snow cover.
.LONG TERM...(Thursday Through Monday)
Issued at 239 AM MST Tue Nov 29 2016
Dry weather expected late this week and this weekend for most of
the area as drier flow aloft from the west-northwest develops over
the region. Weak disturbances in the flow will bring clouds at
times and possibly a few snow showers from far northeast WY into
the Black Hills. Temperatures will mostly be near average through
the weekend, upper 20s and 30s Thursday and Friday, mid 30s to mid
40s over the weekend.
Medium range models have been consistently showing some arctic air
surging into the Northern Plains sometime early next week, mostly in
the Monday night/Tuesday timeframe. Chances for light snow will
likely accompany the arctic air as a large upper trof digs over the
Rockies region. Temperatures look to be well below average Tuesday
and at least the middle of next week.
.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 1028 AM MST Tue Nov 29 2016
MVFR/IFR conditions will continue across the much of the area
through the forecast period...with some gradual improvement
expected through tonight. The exception is VFR conditions across
the southern Black Hills and far southwest SD. Strong
northwesterly winds will continue through this afternoon...with a
few gusts to near 50 kt across the west central SD plains.
SD...Winter Storm Warning until 5 AM MST Wednesday for SDZ001-002-012-
Winter Weather Advisory until 5 AM MST /6 AM CST/ Wednesday for
Wind Advisory until 11 PM MST this evening for SDZ027-041.
High Wind Warning until 11 PM MST this evening for SDZ026-074.
WY...Winter Storm Warning until 5 AM MST Wednesday for WYZ056-057-071.
Winter Weather Advisory until 11 PM MST this evening for WYZ054.