Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 192300
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
500 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 00Z TAFS Through 00Z Monday Evening)
Issued At 500 PM MDT Sun Aug 19 2018

SHRA with associated MVFR/IFR conditions will continue across
south central South Dakota, mostly east of a KPHP to KIEN line,
through the evening before exiting the area. West of the SHRA,
smoke is reducing vsbys to MVFR across most of the area. Eastern
extent of this smoke over MT/ND is poorly represented by guidance,
so pinpointing the timing of improvement from north to south
across our area is difficult. Given trends, think smoke will
persist through tonight and potentially into early Monday
afternoon before conditions improve.

&&

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

$$

DISCUSSION...26
AVIATION...Sherburn



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