Area Forecast Discussion
Issued by NWS Rapid City, SD
FXUS63 KUNR 231717
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1117 AM MDT Sun Apr 23 2017
.SHORT TERM...(Today Through Monday Night)
Issued at 330 AM MDT Sun Apr 23 2017
Upper level analysis shows ridging over the north central and
western CONUS. Mid/high clouds are streaming over the ridge from
the west, and a low cloud deck is filtering in from the north.
At the surface, low pressure is centered over southeast Montana
with a frontal boundary stretching across northern SD.
Temperatures at 3 am are in the 40s with south to southwest winds
at 10 to 20 mph. Winds are out of the northeast across far
northwest SD just north of the frontal boundary.
Today...Upper ridge across the central CONUS will flatten and
shift east as southwest upper flow sets up across the Dakotas. As
weak surface low slides into the Black Hills area, southwesterly
winds will increase across south central SD, with easterly winds
over northwestern SD. This will result in temperatures ranging
from the lower 60s across northwestern SD to the mid 70s across
the southern and central SD plains. Temps in northeastern WY will
be near 70. The first of several upper level shortwaves will
begin moving through the region late tonight, bringing chances
for showers and isolated thunderstorms. Lows will fall into the
40s to lower 50s, with some upper 30s across far northwest SD.
Monday...Southwest upper flow continues on Monday as a broad trof
begins digging into the Pacific Northwest. Sunday nights shortwave
lifts northeast out of the area during the morning hours, with
some lingering showers along the eastern edges of the forecast
area. Should be a little break from precip mid day monday with
highs climbing into the 50s to lower 60s. Next upper shortwave
begins to move into the area by the afternoon, with another round
of showers and isolated thunder across Northeast Wyoming and the
Black Hills area. Showers evolve to more widespread rain during
the evening as main wave crosses the area. Models have trended
upper level temps a bit cooler in the last run, which suggests a
change over to snow across the higher elevations of the Black
Hills late in the evening. Decent amount of liquid available with
this system, so there could be a few inches of wet snow on the
ground by Tuesday morning.
.LONG TERM...(Tuesday Through Saturday)
Issued at 330 AM MDT Sun Apr 23 2017
Rain and snow continues into Tuesday morning as upper shortwave
slides southeast across the area. Looks like temperatures remain
cold enough for snow across the Black Hills through the morning
hours, so a few more inches could accumulate before the system
finally winds down Tuesday afternoon/evening. Could see up to an
inch of snow on the plains Tuesday morning - mainly across
northwest SD and the plains adjacent to the Black Hills.
Unsettled weather continues for the remainder of the week as
shortwave energy crosses the region. The next best chance for
widespread precipitation look to be Wednesday night into
Thursday. Below average highs in the 40s and low 50s are expected
for the rest of the week.
.AVIATION...(For the 18Z TAFS Through 18Z Monday)
Issued At 1111 AM MDT Sun Apr 23 2017
Areas of IFR/LIFR conditions over far nwrn SD will dissipate early
this afternoon and will redevelop after 04Z this evening. VFR
conditions will continue over the rest of the region. Scattered
showers and a few thunderstorms are expected to develop over
northeastern Wyoming and the Black hills starting late this
afternoon and spread into much of the rest of western South
Dakota overnight. Local MVFR conditions are expected near any
showers or thunderstorms.