Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 160528
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1028 PM MST Mon Jan 15 2018

.DISCUSSION...(This Evening Through Monday)
Issued at 137 PM MST Mon Jan 15 2018

20z surface analysis had arctic high over western ND with
clearing skies over the CWA. Main concern this forecast wind
chills.

Tonight into Tuesday morning, arctic high shifts slowly southeast.
Excellent radiational cooling in place with snow cover over 80%
of the CWA. Northerly winds will subside this evening, but then
pick back up some overnight into Tuesday morning as return
southerly flow. Wind chills will bottom out between -15F and
-35F, so will continue current headlines as well as expanding
slightly northwest into far northeast WY.

Tuesday afternoon into Wednesday, fast moving shortwave trough moves
across south central Canada with associated surface low. This low
will drag a warm front through the CWA as upper level ridge pushes
into the northern Plains. Much warmer temperatures expected.

Thursday/Friday, upper/thermal ridge dominates with temperatures
10-15F above normal.

Later Friday into next weekend, pseudo-split flow develops with
weaker northern stream bringing minor disturbances, some PoPs and
cooler temperatures to the CWA. Main storm track looks to remain
southeast of the CWA evidenced by majority of latest ensemble
data. Temperatures will be tricky with tight low level baroclinic
zone hanging out.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Tuesday Night)
Issued At 1028 PM MST Mon Jan 15 2018

MVFR cigs across eastern SD will drift westward into south central
SD through the overnight hours. These will primarily be limited to
areas southeast of a KPHP to KIEN line. Otherwise, VFR conditions
are expected through the TAF period. Continue to think the
potential for wind gusts across northeastern WY on Tuesday will
be limited by a very strong inversion over the lowest 2000 ft,
but may still see a few gusts 20-25 kt.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Chill Advisory until 11 AM MST /noon CST/ Tuesday for
     SDZ001-002-012>014-025-031-032-042>044-046-047-049-072-073.

WY...Wind Chill Advisory until 11 AM MST Tuesday for WYZ054-056-071.

&&

$$

DISCUSSION...Helgeson
AVIATION...Sherburn



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