Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 110517
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1017 PM MST Sun Dec 10 2017

.UPDATE...
Issued at 458 PM MST Sun Dec 10 2017

Forecast updated to let Red Flag Warning expire.

&&

.DISCUSSION...(This Evening Through Sunday)
Issued at 302 PM MST Sun Dec 10 2017

Strong upper ridging continues across the western CONUS...and upper
trough across the eastern two thirds of the CONUS. Upper
wave/clipper system is now quickly crossing Alberta and heading
toward the northern plains. A cold front will cross the area tonight
associated with this wave and a surface low pushing into Minnesota.
Very gusty winds are expected to develop behind the frontal boundary
late tonight into Monday. Cold air advection won`t be real
strong...which is expected to limit the amount of mixing in the low
levels. At this time the belief the 60kt winds at 2000 feet won`t be
able to make it to the surface as gusts. Models are also suggesting
this with sustained advisory criteria speeds. So will go with a high-
end advisory for now and the evening shift can take a look at 00z
models for any needed adjustments. Better mixing is expected Monday
morning with diurnal heating, but by then boundary layer winds will
have weakened enough to continue advisory criteria winds through
much of the day tomorrow. Highs Monday will be in the upper 30s to
upper 40s. The upper ridge will expand eastward through the middle
of next week with warmer air returning to the area. Highs Tuesday
could again approach the 60 degree mark across parts of the western
SD plains. Temps may turn colder later in the week before warming up
again depending on the position of the frontal boundary. Either way
it looks like slightly above to well above temperatures are expected
through the rest of the week. The next decent chance for
precipitation will be Friday night into Saturday as a strong upper
wave crosses the area.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1016 PM MST Sun Dec 10 2017

VFR conditions will continue through Monday afternoon. Northwesterly
winds will become strong overnight as a cold front crosses the
region. Gusts over 45kts are possible over the plains of northwestern
South Dakota. Winds will diminish late Monday afternoon.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory until 2 PM MST Monday for SDZ001-002-012>014-025-
     026-031-032-043-072-073.

WY...None.
&&

$$

Update...7
DISCUSSION...13
AVIATION...7



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