Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 181954

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
154 PM MDT Wed Apr 18 2018

.DISCUSSION...(This Evening Through Wednesday)
Issued at 144 PM MDT Wed Apr 18 2018

An upper low is spinning over IA, while another low is
moving into the Pac NW, with ridging in between. Stratus is
gradually shifting eastward out of the CWA, but some cumulus has
spread across western SD and northwestern WY. Light rain showers
have developed along a stationary boundary, stretching north to
south across western SD. Winds are northwesterly around 10 to 15
mph, and temperatures are rising into the 40s and 50s.

As the upper ridge axis crosses the northern plains, weather will be
dry tonight into Thursday.  Conditions will be favorable for fog
development across mainly south central SD tonight. Temperatures on
Thursday will warm into the 50s, and southeasterly winds will
become breezy ahead of approaching low pressure to the south.

Upper low will swing into the Four Corners region by Friday morning,
and models continue to show a southerly track, keeping most of
the precip south of the CWA. The GFS is more robust than the ECMWF
and Canadian in its expansion of precip across the area.
Temperatures still look warm enough for rain, although a little
light snow will be possible in the Hills.

A mild and dry weekend is expected between systems. Then an upper-
level wave will cross the northern plains Monday, bringing some
light rain, which may change to snow overnight.


.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 118 PM MDT Wed Apr 18 2018

Mainly VFR conditions are expected across the area through
Thursday morning. The exceptions will be across far south central
SD where IFR/LIFR conditions with snow will persist through late
afternoon...improving to VFR this evening. Then areas of fog will
develop after 09Z across south central SD...persisting into early
Thursday morning.




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