Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 152039

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
139 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

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 18Z TAFS Through 18Z Tuesday)
Issued At 955 AM MST Mon Jan 15 2018

MVFR to IFR ceilings are lingering across portions of northeast
WY, along the eastern foothills, and toward central SD. These low
clouds may stick around for a few more hours, before gradually
dissipating this afternoon. VFR conditions are expected elsewhere.
NW winds of 15 to 25 kts will persist today across the western SD
plains, before becoming light and southerly tonight.


SD...Wind Chill Advisory until 11 AM MST /noon CST/ Tuesday for

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



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