Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 212025
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
125 PM MST Sun Jan 21 2018

.DISCUSSION...(This Evening Through Sunday)
Issued at 103 PM MST Sun Jan 21 2018

Water vapor shows upper low developing over sern CO, with surface
analysis placing low center over western KS. Snowfall continues to
diminish across far western SD, but is increasing in intensity
across south central SD as deformation zone intensifies over
central NEB. Will cancel warnings/advisories for both Fall River
and Haakon counties based on radar trends.

Snowfall will continue to increase this afternoon and evening
across south central SD, especially Mellette Todd and Tripp
counties, with upper low deepening even further as it tracks east
across KS. Best lift/snowfall will then transition east of the
region after midnight. An additional 4 to 6 inches snowfall
expected, especially into Tripp county. Winds should continue to
increase across south central SD this afternoon into tonight, but
given the heavy/wet nature of the snow blowing snow will not
become a major factor.

Based on radar trends and latest model data, having adjusted the end
time to 03z for the Winter Storm Warning for Oglala Lakota,
Jackson, and Bennett counties. Will keep the warning going through
the night further east into south central SD, although suspect
all but Tripp county will be cancelled earlier than that.

Weak shortwave in northwest flow will cross the area Monday
evening, with a chance of snow across northeast Wyoming into the
Black Hills. Dry conditions with a warming trend then expected
through Thursday, with temps reaching well into the 50s east of
the Black Hills on Thursday. Next upper trof crosses the northern
plains Friday-Saturday and will bring next chance precipitation.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Monday)
Issued At 1030 AM MST Sun Jan 21 2018

MVFR/IFR conditions with snowfall will continue across far
southwest and south central SD this afternoon, with areas of LIFR
conditions likely. Snowfall will taper off and end from west to
east across these areas during the evening, with conditions
improving to VFR in most areas soon after the snow ends. The
exception will be over parts of far south central SD where snow
will continue through tonight.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Storm Warning until 8 PM MST this evening for SDZ042>044.

     Winter Storm Warning until 6 AM CST Monday for SDZ046-047-049.

WY...None.
&&

$$

DISCUSSION...Johnson
AVIATION...15



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