Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 191746
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1146 AM MDT Fri May 19 2017

.UPDATE...
Issued at 540 AM MDT Fri May 19 2017

Webcams shows poor visibility in snow continuing around Pine Tree
Junction in southern Campbell County, with higher res models
suggesting another band of snow rotating in around mid morning.
Probably not any more significant accums, but maybe another inch.
With slushy roads and poor vsby will extend the advisory through
the morning.

&&

.DISCUSSION...(Today Through Thursday)
Issued at 234 AM MDT Fri May 19 2017

Water vapor shows massive upper low over over wrn CO with
moisture being pulled north out of the srn plains through the nrn
plains. At the surface, high pressure located over nrn ND with
ridge extending swwd into nern WY is stifling the nrn extent of
pcpn across our cwfa. Radar return shows best area of pcpn across
west central SD at this time, although some of the higher returns
are bright banding. Early morning Thermal profiles and webcams
show the snow level around 4000 feet in the Blkhls although not
much has accumulated there. Best accumulations have been across
srn Campbell county with the latest report around 5 inches in
Wright.

Upper low expected to drift slowly ewd through CO today. Pcpn
expected to continue for much of the cwfa this morning, although
nwrn SD will likely see little pcpn given aforementioned surface
ridge. Dry slot showing up on water vapor from cntrl NEB in swrn
SD will likely keep pcpn amounts on the light side this morning
for our area, with pcpn chances then diminishing by the afternoon.
Additional snow accumulations should be rather light across nern
WY into the Blkhls. Will leave the winter wx advisory in place for
srn Campbell county and reevaluate around 6 am to see if it can
expire or needs to be extended.

Best chances for pcpn by tonight will then shift into scntrl SD
as next wave is ejected nwd.

Stacked low then expected to lift newd through the cntrl plains on
Saturday and into the upper midwest Saturday night. Best chances
for pcpn will be in our far ern zones, although some
convergence/instability pcpn possible around the Blkhls.

Warmer conditions expected on Sunday, with some aftn -shra
possible given nw flow aloft. Better chance for -shra on Monday as
strong upper wave embedded in the nw flow crosses the nrn plains.

Low pcpn chances continue early in the week, before upper ridge
builds into the Rockies and dry us out through mid week. Pcpn
chance may return by the end of the week once sw flow aloft
returns. Cool conditions Monday and Tuesday will be replaced by
warmer conditions mid to late week.

.AVIATION...(For the 18Z TAFS Through 18Z Saturday)
Issued At 1145 AM MDT Fri May 19 2017

MVFR conditions in low clouds and light rain will
gradually improve to VFR this evening, except for areas of south
central SD where chances for rain increase overnight. IFR conditions
in light snow over parts of the Black Hills will also improve this
evening.

&&

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

$$

Update...Johnson
DISCUSSION...Johnson
AVIATION...Pojorlie



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