Area Forecast Discussion
Issued by NWS Rapid City, SD
FXUS63 KUNR 171705
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1005 AM MST Fri Feb 17 2017
.SHORT TERM...(Today Through Saturday Night)
Issued at 328 AM MST Fri Feb 17 2017
Current surface analysis shows low pressure over southern SK,
with pacific cold front stretching south-southwest across central
MT into eastern ID/northwest WY. Upper level analysis shows ridge
axis now east of the forecast area, with cutoff low pressure
centered over the southern plains. Southwest flow behind the ridge
is bringing weak shortwave energy across the northern Rockies and
high plains. Mid and high clouds are accompanying this energy,
but lower levels generally too dry for any pcpn across our western
areas this morning. Temps remain very mild, 30s and 40s, with
even some 50s across the northern and eastern slopes of the Black
Hills. Westerly low level jet over the Black Hills area has been
producing some gusty winds to over 40 mph at times overnight
across the warmer areas of the Black Hills, especially the
Spearfish area and the southern Black Hills.
As cool front pushes through later this morning, winds will become
northwesterly across the area and some cooler air will slide in.
However, highs will remain well above average, in the 50s and lower
60s, warmest over southern SD. Winds will be breezy across much of
the area late this morning and afternoon, windy across far northwest
SD, as tighter pressure gradient remains to the north of the
forecast area. Skies will be variably cloudy this morning, with more
sunshine expected in the afternoon. Lows tonight will mostly be in
the mid 20s to mid 30s with some increasing high clouds as high
pressure moves over and eventually east of the area.
Ridge rebuilds over the plains Saturday, with south to southwest
winds developing and pushing some warmer air back into the area.
Highs will be in the mid 50s to mid 60s in most areas. Mid and high
clouds in the morning should give way to more sunshine by the
afternoon. Mild conditions Saturday night with south to southwest
winds persisting. Lows in the 30s and 40s.
.LONG TERM...(Sunday Through Thursday)
Issued at 328 AM MST Fri Feb 17 2017
Upper level ridging will begin to shift east of the area on
Sunday as a shortwave moves across the Rockies. Low level thermal
ridge will be in place over the area, with highs in the 50s and
60s. Some locations will likely be near 70 degrees again,
especially the eastern slopes of the Black Hills and adjacent
plains, as well as parts of south central SD. The shortwave will
cross the area Sunday night and Monday morning, bringing a good
chance for showers. Would not totally rule out possibility of
thunder to the east of the Black Hills Sunday night, but will keep
out of the forecast for the time being. Temperatures could be
cold enough for a mix or change over to snow late Sunday
night/early Monday over the Black Hills.
Some cooler air will briefly push back into the area for Monday, but
remaining quite a bit above seasonal averages. Warmer air will
return again Tuesday, with highs in the 60s across a good portion of
the northeast WY and southern SD plains. Cooler air will begin to
push into the area on Wednesday as large scale trough moves across
the western US. As the trough moves into the plains later Wednesday
night and Thursday, a strong low pressure system is progged by all
longer range models to develop somewhere over the Central Plains.
These models are showing potential for a significant storm over the
region, though way too early to pinpoint where the more significant
pcpn and snowfall could be. Will go with likely pops for most areas
Thursday and Thursday night.
.AVIATION...(For the 18Z TAFS Through 18Z Saturday)
Issued At 1005 AM MST Fri Feb 17 2017
VFR conditions are expected through the forecast period.