Area Forecast Discussion
Issued by NWS Rapid City, SD
FXUS63 KUNR 270531
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1031 PM MST Sat Nov 26 2016
Issued at 914 PM MST Sat Nov 26 2016
Latest model consensus continues to support a deep cyclone over
the northern plains early next week. Although most of the fa
looks to avoid appreciable snows, prolonged moist nw flow looks
to support a long duration upslope snow event in the northern
Black Hills. Temp profiles suggest a long duration of forcing in
the DGZ with steep ll lapse rates. This would support heavy
snowfall rates at times. Given model consensus, impacts, and
gusty nw winds, felt winter storm headlines were justified at
.SHORT TERM...(This Evening Through Sunday Night)
Issued at 206 PM MST Sat Nov 26 2016
Water vapor shows broad upper ridge over the nrn plains, resulting
in sunny skies and temps well into the 50s early this afternoon.
Strong upper trof pushing onshore the west coast will bring big
changes over the next few days.
Upper trof will advance quickly eastward on Sunday, with upper low
beginning to close off over western SD by late aftn, and surface
low deepening over southern SD/northern NE. Temps will be rather
mild much of the day, but will begin cooling late in the day as
northwest winds strengthen on backside of surface low. Some -shra
expected by the aftn, mixing with some snow Sunday night but
little or no accumulation expected. Northwest winds will become
quite strong Sunday night, especially on the western SD plains
with gusts over 40 mph.
.LONG TERM...(Monday Through Saturday)
Issued at 206 PM MST Sat Nov 26 2016
Upper level low will be positioned somewhere to the east-
northeast of the forecast area Monday morning, likely over
northeastern SD or southeast ND, then move slowly east through the
early part of the week. 12z/18z runs of the medium range models
showing better agreement on track of low into Monday, but differ a
bit on the extent of eastern movement after Monday as blocking
pattern to the east complicates matters. As the low hangs to the
east of the area, shortwave energy and moisture will wrap around
the system, bringing areas of mostly light snow from Monday
through at least Tuesday, along with gusty northwesterly winds.
The best chances for snow across the plains at this point will
generally be across northwest SD into central SD. A prolonged
period of upslope snowfall is likely across the northern Black
Hills from late Monday into Tuesday night as strong and relatively
moist north-northwest flow remains across the area. Several inches
of snow is looking increasingly likely through the period over the
northern Hills. Elsewhere, accumulations of up to a few inches
look possible early next week from northwest SD into portions of
central SD, with very light accumulations possible elsewhere.
Gusty winds would cause some blowing and drifting of any snow that
Improving conditions are expected mid week, with the latter part of
the week into the weekend looking mainly dry. Temperatures through
the week will be near or below average, with highs mostly in the
upper 20s and 30s from Tuesday through Friday.
.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1029 PM MST Sat Nov 26 2016
VFR conditions are expected through the period. Breezy ssw winds
can be expected across portions of northeast WY and into the Black
Hills tonight. A low pressure system will push through the region
Sunday afternoon with winds shifting nw behind a cold front, and
becoming gusty sunday night.
SD...Winter Storm Watch from Monday afternoon through late Tuesday
night for SDZ024-025-028.
WY...Winter Storm Watch from Monday afternoon through late Tuesday
night for WYZ057.