Scientific Forecaster Discussion
fxus63 kunr 171028
Area forecast discussion for western South Dakota and northeastern Wyoming
National Weather Service Rapid City South Dakota
428 am MDT Thu Oct 17 2019
Discussion...(today through wednesday)
issued at 314 am MDT Thu Oct 17 2019
Current surface analysis shows low pressure over southern sk,
with a warm front extending south-southeast through the Dakotas.
Further west, a cold front is in place across the Pacific northwest.
Upper level analysis shows a ridge over the High Plains, with a
trof along the West Coast. Some high clouds are passing through
the ridge. Otherwise, skies are mostly clear. Temps are mostly in
the mid 30s to upper 40s. Winds are generally light from the west
A warm day is on tap, with highs in the 70s to around 80 degrees
across the plains. Southwesterly winds will become breezy over
northeast Wyoming into parts of southwest SD, with southerly winds
elsewhere. Cold front well to the west will move quickly east across
the region later tonight and early Friday, bringing much cooler air
back to the area, along with gusty northwesterly winds. A few
showers are possible with a shortwave trough moving through late
tonight and Friday, especially across northeast Wyoming and the Black
Hills, but any pcpn amounts should be very light. Winds could
approach low end advisory criteria on Friday across portions of the
northwest and west central South Dakota plains.
The weekend looks to be a mixed bag. Saturday will be the nicer of
the two days as shortwave ridge moves quickly across the area. Highs
will be near seasonable levels Saturday, mostly 50s and lower 60s.
Fast moving trough will dig southeast across the region Saturday
night and Sunday, likely intensifying as it moves east of the area
later on Sunday. Medium range models in decent agreement on general
track and timing of system at this point, with some relatively minor
differences on where the system intensifies and extent of colder air
and pcpn chances. The better chances for pcpn still look to be
mostly east of the Black Hills, and especially toward central SD,
Sunday afternoon and evening. Forecast temps in the lower levels
would mainly support rainfall, especially to the east of the Black
Hills, but could be cold enough for some snow across northeast Wyoming
and the Black Hills Sunday on the back side of the system. Highs on
Sunday will mostly be in the 40s, with 50s south and east of the
Black Hills. Strong northwesterly winds could develop on the back
side of the system as low pressure strengthens to the east of the
area by Sunday afternoon.
The first half of next week looks to be relatively cool, but near or
slightly below average overall. Most areas should stay dry Monday
and Tuesday, though likely breezy with fast northwest flow aloft.
Another system sometime midweek should bring the next good chance
for pcpn in the form of rain and possibly some snow for at least
northeast Wyoming and the Black Hills as colder air likely accompanies
Aviation...(for the 12z tafs through 12z Friday morning)
issued at 426 am MDT Thu Oct 17 2019
VFR conditions are expected through this evening. Gusty southwest
winds will develop over northeast Wyoming into far southwest South Dakota late
this morning through this evening. A cold front will move through
tonight with gusty northwest winds behind it. Local MVFR ceilings may
develop in association with very light showers over northeast Wyoming
into the Black Hills late tonight.
issued at 314 am MDT Thu Oct 17 2019
A period of critical fire weather conditions is expected this
afternoon across much of the northeast Wyoming plains into parts
of the far southwest South Dakota plains, where a red flag warning
is in effect. Highs will be in the 70s, with relative humidities
dropping to 10 to 15 percent and southwesterly winds increasing to
15 to 25 mph with some higher gusts, especially across northeast
Wyoming. A cold front will move through later tonight, with winds
shifting to the northwest behind it.
South Dakota...red flag warning from 10 am this morning to 8 PM MDT this
evening for sdz322-326.
Wyoming...red flag warning from 10 am this morning to 8 PM MDT this
evening for wyz314>317.