Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 200454
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1054 PM MDT Sun Aug 19 2018

.DISCUSSION...(This Evening Through Sunday)
Issued at 255 PM MDT Sun Aug 19 2018

Current surface analysis shows low pressure over southwestern MN,
with cold front stretching across southern portions of SD. Upper
level analysis shows low over eastern NE, with trough starting to
move east of the region. Skies have started to clear over
northeast WY and northwest SD, with clouds and showers lingering
to the east and southeast of the Black Hills. Temps are on the
cool side, mostly in the upper 50s and 60s, with 50s over the
Black Hills. Northwesterly winds remain brisk across the SD
plains, but are starting to decrease.

Cooler weather will linger through the first part of the upcoming
week, then more seasonable temperatures will return for Wednesday
through next weekend. A relatively dry week looks to be on tap,
though weaker disturbances will bring isolated to scattered showers
to parts of the area Monday night into Tuesday and possibly some
storms late Thursday. Smoke from wildfires to the west and northwest
of the region will affect the area at times and at least keep skies
hazy through much of the week.

For late today and tonight, showers will continue to diminish from
northwest to southeast across southwest and central SD, exiting
south central SD by late tonight. Winds will diminish and clouds
will decrease, with lows mostly in the mid 40s to mid 50s as drier
air moves in from the north and west. Will likely see some upper 30s
over the higher Black Hills early Monday.

Highs Monday and Tuesday will be in the 70s across the plains, with
60s over much of the Black Hills. Weak ridging over the Rockies will
bring drier weather. However, a disturbance will eject out of an
area of low pressure along the west coast and will likely bring some
showers Monday night into Tuesday across northeast WY and a good
portion of western SD.

The weak ridge shifts into the plains midweek, with highs back into
the 80s for most areas through late week. Upper low over the west
coast weakens midweek and eventually moves into the Northern Plains
later Thursday. Depending on the track, could see another round of
showers and storms during this time, with the better chances at this
point looking to be across northern portions of the forecast area.
The weekend looks mainly dry at this time, but a larger upper level
system is progged to settle into the Pacific NW during this time,
with southwest flow aloft eventually developing from the Rockies
into the Northern Plains. Depending on the track and timing, we
could see some increasing chances for storms, especially toward the
latter half of the weekend.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1054 PM MDT Sun Aug 19 2018

Few lingering -SHRA and associated MVFR/IFR conditions should
exit south central SD over the next couple of hours.

Smoke has generally dispersed sufficiently over western SD for
conditions to return to VFR, though MVFR conditions in FU/HZ
persist over northeastern WY. Latest smoke forecasts suggest
concentrations will remain about constant through mid-morning over
northeastern WY before conditions improve, so will maintain MVFR
conditions at KGCC through 15z Monday. It is plausible that
upper-level smoke could mix close to the surface tomorrow afternoon,
thus reducing vsbys again across western SD.

Otherwise, VFR conditions will prevail before SHRA arrive from
the west Monday evening.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

DISCUSSION...26
AVIATION...Sherburn



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