FXUS63 KUNR 260828

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
228 AM MDT Wed Sep 26 2018

.DISCUSSION...(Today Through Tuesday)
Issued at 228 AM MDT Wed Sep 26 2018

Shortwave ridging ongoing ahead of the next fast moving impulse.
WAA has ensued with ongoing pressure falls supporting a mixed BL
at many places, esp around ridges and downslope areas. This has
allowed temps to hold around 40 at many locations, limiting frost.
Much warmer conds expected today as warm downslope SW flow
spreads over the area ahead of a shortwave trough. Sfc low will
quickly progress through the area today, with a strong cold front
expected into the area later tonight. FGEN precip band will slowly
settle south into the region through Thurs, with chances for rain
INVOF this feature as it shifts south. PAC origin moisture in NW
flow will limit precip potential outside of the terrain forced
areas of NE WY and the Black Hills, with mostly light rain or
sprinkles expected. Temps will peak early for most of the FA
Thurs, with falling temps expected in the afternoon as CAA
continues. Cooler numbers than current forecast values are
certainly possible for Thur given concerns on clouds, precip, and
strength of the CAA. Frontal boundary will briefly stall just
south of the FA as secondary impulse and associated jet streak
moves through the region Thur night. This will support a good
chance for light rain and snow across NE WY into SW SD in this
period, esp given jet streak position. Some light snow accums will
be possible over portions of NE WY and the the Black Hills given
thermal fields. SfC ridge will build into the region Fri, with
fall temps expected as many locations will struggle out of the 40s
for highs. Western CONUS ridge will breakdown this weekend,
supporting local height rises as the baroclinic zone shifts back
over the region. This will support unsettled conds into early next
week with the jet stream over the region. Confidence in temps
during this period remain low given the region's proximity to the
progged frontal zone. Although if progged SW flow develops, more
mild conds should be in store, in line with ECMWF ensemble means
toward early next week.


.AVIATION...(For the 06Z TAFS Through 06Z Wednesday Night)
Issued At 958 PM MDT Tue Sep 25 2018

VFR conditions are expected through Wednesday.


SD...Frost Advisory until 8 AM MDT this morning for SDZ001-002-012-

Freeze Warning until 8 AM MDT this morning for SDZ041-042.

WY...Frost Advisory until 8 AM MDT this morning for WYZ054>056-058-



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