Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 210504

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1104 PM MDT Thu Oct 20 2016

.SHORT TERM...(This Evening Through Friday Night)
Issued at 145 PM MDT Thu Oct 20 2016

Upper level analysis has trof shifting east into the Great Lakes
region, and ridge building across the Northern Rockies. Skies are
mostly sunny across the Northern Plains. At the surface, high
pressure resides across the eastern Dakotas, with lee trof
strengthening across central MT and eastern WY. Temperatures at
2pm are in the 50s to around 60 degrees, with light west to
southwest winds.

Tonight...Upper ridge will continue to build across the western
CONUS with a weak shortwave topping the ridge. Cloud cover will
increase overnight but any precip will be well north of the
forecast area. Low temperatures will be in the 30s.

Friday...Weak upper shortwave will shift east with western ridge
continuing to build over the Northern Plains, leading to sunny
skies by afternoon. Temperatures will be well above average, with
highs in the 60s to lower 70s. Mostly clear skies expected Friday
night with lows in the 30s to lower 40s.

.LONG TERM...(Saturday Through Thursday)
Issued at 145 PM MDT Thu Oct 20 2016

Eastern pac troughing will persist through the period as fast
westerly disturbed flow over the northern pac supports trough re-
loading there. This will continue to support downstream mean
ridging. Flow will remain progressive with periodic disturbances
ejecting out of the persistent trough. This will support fairly
mild weather in the period, esp ahead of each impulse in sw flow,
with 50s-70s for highs and 30s/40s for lows. Mean storm track
looks to remain over or just north of the fa, which supports dry
weather locally. The only concern in the period will be fire
weather with very dry westerly flow and potentially breezy conds
at times.


.AVIATION...(For the 06Z TAFS Through 06Z Friday Night)
Issued At 1103 PM MDT Thu Oct 20 2016

VFR conditions are expected through Friday night.


Issued At 145 PM MDT Thu Oct 20 2016

Dry west-southwest flow will develop over the area on Saturday.
Minimum relative humidity values will be 15-25% over much of the
CWA, especially southwestern SD and parts of northeastern WY.
Winds speeds look marginal at this time, with a low probability of
prolonged winds of 25 mph or higher. The determining factors will
be timing of the trough and mixing heights.




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