Area Forecast Discussion
Issued by NWS Rapid City, SD

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723
FXUS63 KUNR 142333
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
433 PM MST Wed Feb 14 2018

.DISCUSSION...(This Evening Through Wednesday)
Issued at 236 PM MST Wed Feb 14 2018

Upper level analysis has near zonal flow across the northern
Plains, with a trof along the CA coast. Skies are mainly clear
across most of the area with cloudy skies across northwest SD.
At the surface, high pressure resides across the central Plains
with weak lee trof along the northern Rockies. Temperatures range
from the upper 30s over portions of northwest SD, to the 40s over
south central SD.

Clouds will continue to increase from the north and west this
evening as the next cold front slides south across MT and ND. Low
temperatures will fall into the teens to lower 20s.

The front will shift south across the forecast area early
Thursday morning. The best chances for snow will be across
northeast WY into the northern Black Hills and parts of northwest
SD, where 1 to 2 inches are possible. Elsewhere, less than an inch
is likely, with south central SD likely seeing minimal snowfall.
Gusty northwest winds on Thursday behind the front could produce
blowing and drifting of snow in spots across the plains.
Temperatures on Thursday will be in the teens to upper 20s. System
clears the area Thursday evening with Arctic high pressure sliding
across the Black Hills.

The coldest air will only be here for a brief time, mainly late
Thursday night into Friday morning, before rising back to near
average levels for at least Friday afternoon and Saturday. Some
unsettled and colder weather is likely to return for Sunday and
into early next week as a broad trough is progged to dig south
across the western states. Some significant accumulating snowfall
is looking increasing likely Sunday night into Monday, as a strong
storm system ejects out of the central Rockies. EC and GFS still
differ on the track of this system, with the EC showing best
chances across the Black Hills into northwest SD, while the GFS is
further south across southern portions of SD. Arctic air settles
in across the northern Plains for the middle of next week.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Thursday Evening)
Issued At 431 PM MST Wed Feb 14 2018

Conditions will deteriorate to MVFR/IFR behind a cold front across
northwestern SD/northeastern WY as low cigs/-SN arrive around
after midnight. Brief drops to LIFR vsbys will be possible in
heavier snow Thursday morning. Northwesterly winds will increase
Thursday morning and remain strong into the afternoon, with gusts
approaching 30-40 kt across portions of western SD, including at
KRAP, after 15z. Conds will improve NW-SE THur afternoon as the
system exits the region and drier works in.

&&

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

$$

DISCUSSION...15
AVIATION...JC



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