Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 121707

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1107 AM MDT Mon Mar 12 2018

.DISCUSSION...(Today Through Sunday)
Issued at 157 AM MDT Mon Mar 12 2018

08z surface analysis had ridge across the northern Plains, just
east of the CWA. Weak return flow noted over WY ahead of shortwave
spinning over western WY. High clouds spreading into CWA ahead of
this feature.

Today/tonight, shortwave drops southeast with little low level
moisture as upper ridge builds into the Rockies. A increase in
high clouds expected this morning, then clearing this afternoon.
Weak low level warm air advection will push temperatures to near
normal, except over the snowpack. Lows tonight will be near
guidance. Any patchy fog early this morning or late Monday night
should be fleeting.

Tuesday/Wednesday, upper ridge will dominate the weather with
thermal ridge developing. Spring-like weather expected with highs 10-
15F above normal, except over the snowpack.

Thursday will be a transition day as upper ridge moves east and
upper trough/psuedo-split flow-type pattern sets up over the western
CONUS. Temperatures will be slightly cooler than Wednesday.

Friday, model spreads increase. 00z EC/Canadian show upper low
developing over NE, but GFS has open wave moving across MT. PoPs
warranted, but actual impact weather confidence low at this time.

Saturday through Monday, model run-to-run consistency as well as
model differences apparent. Some sort of potentially impactful
storm system may move into the central/northern Plains. Cooler
unsettled weather should occur.


.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1105 AM MDT Mon Mar 12 2018

VFR conditions are expected through this afternoon. MVFR/IFR
conditions in fog will develop this evening across much of the
western SD plains, lingering into Tuesday morning.




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