Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 092130
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
230 PM MST Fri Dec 9 2016

.SHORT TERM...(This Evening Through Saturday Night)
Issued at 230 PM MST Fri Dec 9 2016

Northwest flow aloft continues today across the northern Plains
and into the eastern CONUS...with a 115kt jet streak across MT
pushing into the Dakotas. At the surface...1042mb arctic high
pressure sits across the Dakotas with generally weak northeasterly
winds across the CWA. Frontal boundary currently sits across
ncentral WY into the Neb panhandle with CYS reporting lower 40s
while much of the CWA is in the single digits. Snow from this
morning has ended with just flurries persisting across the area.
Weak ridging will develop across the nrn Rockies tonight as the
front begins to slowly move northeastward. The boundary is progged
to move into northeast WY and southwest SD late tonight into the
Black Hills area Sat morning before stalling out. Lows tonight will
be in the single digits but will slowly rise late tonight as the
front pushes in. Wind chills look to be at -15 up to -25F across
northwest SD...so not enough for wind chill headlines. Highs
Saturday will vary greatly depending on the side of the front...with
northwest SD in the single digits while northeast WY and southwest
SD reaches the low 30s. The biggest gradient could be along the
northern foothills as the Black Hills warm into the low 30s and the
surrounding plains reach the upper teens to low 20s...or potentially
colder if the arctic airmass has a tough time getting flushed out.

As the front pushes into the area tonight...increasing isentropic
lift will develop across southwest SD and the Black Hills area this
evening...then slide northeastward just ahead of the surface front
overnight. This band of snow will then move into central SD by Sat
morning. Accumulations will be light...under an inch. Most areas
will see drier weather during the day tomorrow on the backside of
the departing snow. Upper flow will become zonal with a strong
shortwave crossing the Cascades and northern Rockies. 800mb low will
cross the CWA Sat evening with chances for snow increasing again
through the night. Colder air will push back into the area on the
backside of the low as it pushes E/SE of the CWA.

.LONG TERM...(Sunday Through Friday)
Issued at 230 PM MST Fri Dec 9 2016

Fast moving shortwave exits the area early Sunday. May be some
lingering light snow across southwest South Dakota, otherwise some
sunshine and slightly warmer temperatures expected. Sunday will be
the warmest day of the extended, even though temperatures will be
10-15F below average. Reinforcing shot of arctic air arrives
Monday, with falling afternoon temperatures. Dry weather expected
for the middle of the week with highs 20-25F below average.
ECMWF/GEFS still pointing to widespread snow next weekend, along
with the very cold temperatures.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Saturday Evening)
Issued At 230 PM MST Fri Dec 9 2016

Areas of MVFR/LCL IFR conditions in light snow and stratus will
linger across northwest into south central South Dakota through
early evening. Widespread IFR conditions with snow is expected to
develop tonight and continue into Saturday morning, with MVFR/IFR
cigs lingering into Saturday afternoon.

&&

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

$$

SHORT TERM...13
LONG TERM...7
AVIATION...7


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