Area Forecast Discussion
Issued by NWS Rapid City, SD

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404
FXUS63 KUNR 202315
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
515 PM MDT Fri Oct 20 2017

.DISCUSSION...(This Evening Through Friday)
Issued at 300 PM MDT Fri Oct 20 2017

Current surface analysis shows lee trough over the Black Hills
area, with trailing cold front from eastern MT through central WY.
Upper level analysis shows southwest flow over the area, ahead of
large trough over the west coast and the Great Basin. Skies are
mostly sunny with temps in the 70s and lower 80s. Southwesterly
winds are gusting at 30 to 40 mph at times across northeast and
much of western South Dakota.

Cold front will track across the area during the evening and into
the overnight hours, exiting east of the CWA late tonight. Gusty
northwest winds will develop for a period behind the front,
especially across northwest SD, where advisory criteria winds are
expected at times through Saturday. Shortwave energy behind the
front will bring isolated to scattered showers overnight into early
Saturday, with the better chances more likely toward south central
SD where there will be more moisture available. A thunderstorm or
two is also possible late tonight over south central SD. Cooler air
filtering in will drop lows into the upper 30s and 40s.

Much cooler air will be in place across the area for Saturday, with
highs only in the 50s and lower 60s. Any lingering showers over
eastern portions of the CWA should exit in the morning, with partly
cloudy skies across the area. Gusty winds will continue across much
of the plains, strongest over northwest SD, where gusts to around 50
mph are expected. Winds will taper off late in the day.

Cooler air will be short-lived as warmer air advects in later
Saturday night and Sunday. Highs will mostly be in the mid 60s to
mid 70s on Sunday with variably cloudy skies and west to southwest
winds. Another cold front passage Sunday night will bring gusty
winds and cooler air for early next week. There could also be some
rain showers Sunday night and early Monday, especially from
northeast WY to southwest SD.

The see-saw with temperatures will likely continue through much of
next week. Warmer air will return by midweek before another cold
front is progged to cross the region Wednesday night into Thursday
with colder air, gusty winds, and some showers.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Saturday Evening)
Issued At 513 PM MDT Fri Oct 20 2017

VFR conditions will continue through the period. A strong cold
front will slide across the area this evening into the overnight
hours, with gusty northwest winds behind the front. Winds will
become northwesterly behind the front. A few gusts to 45 knots
will be possible across NE WY and NW SD right behind the front. A
few showers are possible behind the front, especially east of the
Black Hills, with ISOLD TS also possible across scentral SD.
Breezy NW winds will continue through the day Sat.

&&

.FIRE WEATHER...
Issued At 300 PM MDT Fri Oct 20 2017

Warm, dry, and breezy weather will continue to produce Red flag
conditions into this evening across much of northeast WY and
western SD. A cold front will cross the area during the evening,
bringing gusty northwest winds and much cooler air overnight.

Saturday will be 20 to 25 degrees colder, but still relatively dry
with gusty winds across the plains, especially northwest SD. The
grassland fire danger is forecast to be in the very high to extreme
category across much of the northwest and west central SD plains.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning until midnight MDT tonight for SDZ260>264.

     Wind Advisory from 9 PM this evening to 6 PM MDT Saturday for
     SDZ001-002-012-013.

WY...Red Flag Warning until midnight MDT tonight for WYZ259-297>299.

&&

$$

DISCUSSION...26
AVIATION...JC
FIRE WEATHER...26



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