Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 080852
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
152 AM MST Fri Dec 8 2017

.DISCUSSION...(Today Through Thursday)
Issued at 150 AM MST Fri Dec 8 2017

Fast northerly upper flow covers the northern plains
as a 130 kt jet dives south from Canada. A broad trough stretches
over the eastern CONUS and into Texas, while a high-amplitude ridge
builds over the west coast. Skies across the Dakotas are partly
cloudy. Northwest winds are gusty, especially just east of the Black
Hills, where a tight pressure gradient over the Hills is creating
strong downsloped winds. Gusts of 60+ kts have been reported in
several locations early this morning. Temperatures at 2 AM are in
the mid 30s to lower 40s.

Winds may decrease a little this morning as the pressure gradient
slackens, but then increase again late this morning into this
afternoon. HRRR forecast sounding shows 35-50 kt winds mixing down
at RAP late this morning. Will keep High Wind Warning out through
the afternoon for areas just east of the Hills, with a Wind Advisory
for the northern foothills. Highs today will be in the 40s on the
plains and 30s in the Black Hills.

Upper ridging will spread over the area this weekend, allowing
temperatures to warm into the 40s and 50s Saturday, and 50s to lower
60s Sunday. Breezy to windy conditions will continue through the
weekend under strong northwest flow. NAM is showing a tightening
pressure gradient over the Hills for the next few nights...not as
strong as this morning, but have adjusted winds up a bit over the
northeastern foothills Saturday and Sunday mornings for any
downsloping that may occur.

A clipper will cross the Dakotas Sunday night into Monday. Although
precip should stay east of the CWA, another round of gusty winds can
be expected, along with cooler (but still above average)
temperatures. Both the GFS and ECMWF show temps rebounding for
Tuesday, before another clipper brings some cooler and breezy
weather for Wednesday.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Friday Night)
Issued At 1016 PM MST Thu Dec 7 2017

VFR conditions expected through the period with gusty WNW winds,
especially east of the Black Hills.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...High Wind Warning until 5 PM MST this afternoon for SDZ026-031-
     072-073.

     Wind Advisory until 5 PM MST this afternoon for SDZ025.

WY...None.
&&

$$

DISCUSSION...Pojorlie
AVIATION...JC



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