Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 130441

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1041 PM MDT Mon Mar 12 2018

.DISCUSSION...(This Evening Through Monday)
Issued at 232 PM MDT Mon Mar 12 2018

Latest upper analysis shows a high amplitude upper ridge over the
western CONUS with a weak vort max dropping down the east side of
the ridge, currently moving from swrn SD into nwrn NEB. Radar is
showing some weak returns associated with this feature over wrn
NEB however with cloud bases around 10kft mainly virga is the

At the surface a N-S oriented band of high pressure over
the great plains will lead to light southeasterly winds over much
of the forecast area tonight. There may be enough low level
moisture for areas of upslope fog to form tonight into Tuesday

For Tuesday through Thursday, the upper ridge will lead to high
temperatures 10-15F warmer than average, except over the snowpack
in northwestern South Dakota.

On Friday, the spread between the model solutions begins to
increase. Some showing a stronger closed low and others just an
open wave. PoPs warranted, but actual impact weather confidence
low at this time.

Saturday through Monday, model run-to-run consistency as well as
model differences continue. A potentially impactful weather
system may move into the central/northern Plains. Cooler unsettled
weather should occur.


.AVIATION...(For the 06Z TAFS Through 06Z Tuesday Night)
Issued At 1041 PM MDT Mon Mar 12 2018

FG/BR is beginning to develop over portions of the northern SD
plains this evening. Short-term model consensus appears to be
handling location of this activity quite well, though it is tough
to gauge intensity due to limited obs in the area. Continuing
through the night, should see more widespread FG/BR development
and associated MVFR/IFR conditions over the SD plains,
particularly in areas that still have snowpack.

Believe BR will impact KRAP with MVFR cigs/vsbys beginning around
11z, though lingering high clouds may further delay its onset.
Remains plausible that FG/BR and associated lowered cigs/vsbys
could remain east of the site through the night.

VFR conditions are expected area-wide through the day Tuesday.




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