Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 202054
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
254 PM MDT Tue Sep 20 2016

.SHORT TERM...(This Evening Through Wednesday Night)
Issued at 238 PM MDT Tue Sep 20 2016

Water vapor shows deep upper trof working onshore the pac nw with
broad wsw flow extending through the nrn plains. At the
sfc...broad low pressure covers the cntrl plains/cntrl rockies
region with nearly stationary frontal boundary extending from ern
Wy through nrn NEB.

Tonight...weak wave energy embedded in the fast w/sw flow will
bring a chance of convection to far nwrn SD...with most activity
remaining over ND. Sfc high pressure will build swd into the nrn
plains with increasing nely bl flow. This moist upslope flow will
aid in low stratus development acrs much of the area...especially
on the SD plains/foothills...and both NAM/SREF showing fairly high
probabilities for fog/drizzle towards daybreak. Lowest
visibilities likely to be terrain dependent.

Wednesday...Areas of fog/drizzle will persist through the morning.
Improvement expected on the plains by aftn...although it`s
possible it will persist around the Blkhls/foothills through the
day. Have lowered high temps over much of wrn SD given limited
insolation.

Wednesday night...Low stratus/fog once again will be an issue with
persistent nely bl flow. Chances for pcpn will begin to increase
as upper low digs into the Great Basin and flow aloft turns more
swly.

.LONG TERM...(Thursday Through Tuesday)
Issued at 238 PM MDT Tue Sep 20 2016

Upper low will moving eastward across the western CONUS on
Thursday, with southwest flow bringing moisture and increasing
precipitation to the CWA. There may also be some fog across
portions of the area Thursday morning. Upper low still expected to
affect the region through the end of the week. ECMWF and GFS still
in relatively good agreement through the GFS leans toward a larger
cut off low farther south of the main upper flow. The low will
cross the region through the weekend bringing good chances for
precipitation Fri-Sat. Dry slot will dry things up Sat night
through early next week with the exception of wrap around precip
possible early Sunday. Temperatures will be generally near to
below average Thursday through Saturday, with the exception of
south central SD. Cooler air will push into the area on Sunday.
Warmer weather is expected after Sunday.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 238 PM MDT Tue Sep 20 2016

Mainly VFR conditions are expected through tonight.
MVFR/IFR CIGs and VSBY are expected to develop late tonight through
Wed morning with areas of fog or even drizzle possible. These
conditions are expected to be mainly across the western SD plains.

&&

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

$$

SHORT TERM...Johnson
LONG TERM...13
AVIATION...13



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