Area Forecast Discussion
Issued by NWS Rapid City, SD

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179
FXUS63 KUNR 300509 CCA
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1036 PM MDT Sat Apr 29 2017

.DISCUSSION...(This Evening Through Saturday)
Issued at 201 PM MDT Sat Apr 29 2017

Mean troughing will continue over the region through mid next
week with a few systems bringing chances for precip at times. Deep
closed low over the SW CONUS coupled with a stalled frontal
boundary over the southern plains will slowly progress
east/northeast through Sunday. Pos theta-e advection coupled with
high centered FGEN will support enough lift over the far SE late
tonight into Sunday to support precip there, mainly Tripp county
east. However, a sfc ridge to the north will continue fight the NW
extent of precip given amount of dry air affecting in from the NE
at low levels. Hence, have opted for a sharp NW cutoff to any
precip chances there. Precip may mix with or change to snow Sunday
night from Tripp county and east with light accums possible,
hinging on the NW extent of moisture/lift. Have opted for around
an inch attm. As this system shifts east, another fast moving
clipper like system will advect into the region Sunday
night/Monday morning from the NW. This could support a few
rain/snow showers in the far west. The associated cold pool from
this system will support steep ll lapse rates Monday afternoon,
generating some small CAPE over the region, enough to support a
few showers perhaps a few TS. It will also be quite breezy Monday
given strong linked flow aloft and expected deep mixing, windiest
across NW SD where adv winds look likely. A stronger system will
then arrive Tues, supporting a decent chance for rain showers and
possibly a TS. Still some questions on track and moisture
availability, which would impact thermal fields and precip
chances. A few snow showers will also be possible Tues evening
above 6 KFT with any lingering activity. After Tues, the pattern
begins to shift with massive ridging progged over the western
CONUS. This will support much warmer conds and dry weather the
remainder of the week, with 70s and 80s expected toward the end of
next week. GOMEX looks to be shutdown by late next week given a
strong cold front pushing through that region mid next week. This
will highly limit moisture availability with a potential passing
trough next weekend.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1034 PM MDT Sat Apr 29 2017

VFR conditions expected through the period for all but south-
central SD. There, rain/snow showers will slowly move into the
area by morning and persist through Sunday. This will be
associated with some MVFR CIGS and VSBYS on Sunday. Elsewhere,
some patchy fog is possible overnight over parts of Campbell and
Weston Counties in WY where snow melted Saturday and will allow
for high RHs to develop tonight.

&&

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

$$

DISCUSSION...JC
AVIATION...Bunkers



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