Area Forecast Discussion
Issued by NWS Rapid City, SD

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710
FXUS63 KUNR 101645
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
945 AM MST Sat Dec 10 2016

.UPDATE...
Issued at 934 AM MST Sat Dec 10 2016

Temps across the northeast WY and western SD plains remain in the
single digits this morning...however warmer air associated with a
frontal boundary just south of the CWA is inching northward. The
12z KRAP sounding prominently shows this warmer air aloft. Surface
obs across the Black Hills have now risen into the 20s to low 30s.
The big question today is how far this warmer air will reach into
the plains. Think with easterly component to the surface winds
across the western SD plains...temps will struggle to warm even
into the 20s along the northern and eastern foothills of the Black
Hills...perhaps all the way into Fall River county. Have dropped
max temps across these locations. Over in northeast WY plains temps
also remain in the single digits but think the warm front has a
much better chance of pushing into this area. Pine Tree Junction
has already risen 20 degrees above this morning`s low so warmer
air is beginning its northeastward push. Rest of the forecast is
in good shape.

&&

.SHORT TERM...(Today Through Sunday Night)
Issued at 216 AM MST Sat Dec 10 2016

A low-amplitude upper ridge covers the western CONUS, with a low-
amplitude trough over the east. Surface high sits over eastern ND,
and southeasterly return flow is developing over the CWA. A
surface trough stretches over the Rockies. Radar shows a band of
snow from the northern Hills into south central SD and Nebraska.
Under cloudy skies, temperatures are in the single digits above
and below zero.

Band of snow will shift into central and eastern SD today as low-
level trough gradually pushes through the northern plains.
Accumulations will be light, generally less than an inch. A warm
front will move into southwestern portions of the CWA with the low,
allowing temps there to rise into the 20s and lower 30s. However,
arctic airmass will linger over northern SD, keeping highs there in
the single digits. Skies will be mostly cloudy.

A fast-moving upper level shortwave will cross the northern plains
tonight, bringing another round of light snow. Accumulations will be
light if any, with higher accumulations expected over ND and eastern
SD where there is better upper forcing.

Weak, brief ridging and westerly low-level flow will allow for a
mainly dry day Sunday, as well as the warmest temperatures for the
next week or so. Highs will warm into the 20s across much of the
CWA, with some teens over northern SD and some 30s over southwestern
SD. Lows tonight and Sunday night will be in the single digits and
teens.

.LONG TERM...(Monday Through Friday)
Issued at 216 AM MST Sat Dec 10 2016

A reinforcing shot of arctic air will arrive on Monday with
breezy to windy northwest winds and falling afternoon
temperatures. There is a slight chance of light snow or flurries
as the colder air flows into the region. For Tuesday through
Thursday, light is snow possible each day over parts of
northeastern Wyoming and southwestern into south central South
Dakota as warmer air pushing up from the south overruns the colder
air at the surface. High temperatures will continue to run 20-25F
degrees colder than average. Extended models still indicate
widespread snow next weekend, as even colder air pushes southward
into the forecast area.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 934 AM MST Sat Dec 10 2016

Widespread MVFR/IFR cigs with periods of light snow/flurries will
continue occur over western and central South Dakota today and
tonight. The lower ceilings and light snow will move into
northeastern Wyoming this afternoon and continue into tonight.

&&

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

$$

Update...13
SHORT TERM...Pojorlie
LONG TERM...10
AVIATION...7



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