Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 212316

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
516 PM MDT Wed Mar 21 2018

.DISCUSSION...(This Evening Through Wednesday)
Issued at 224 PM MDT Wed Mar 21 2018

An upper ridge is building over the western and central CONUS,
with a trough over the east. Skies are mostly sunny across the
northern plains. A surface high rests over northwestern SD, and a
warm front stretches across northeastern WY into south central SD.
Temperatures to the south of the front are in the 40s and lower
50s, with temps to the north in the 30s. Winds are light from
varying directions.

Light southeasterly winds will develop across the SD plains tonight.
Surface moisture looks sufficient for some fog, although models have
backed off slightly, as winds may be a bit stronger and RH a bit
lower than previously forecast. However, conditions still look
favorable enough to mention patchy fog.

Dry weather will continue into Thursday, as the upper ridge axis
begins to cross the region. The pressure gradient will tighten ahead
of an upper wave, and breezy southeasterly winds will keep
temperatures near or slightly cooler than today`s highs. Thursday
night, precipitation will spread across the CWA. Type will be mainly
rain, although soundings are indicative of some freezing rain across
northwestern SD.

Chances for rain will continue into Friday, and Saturday will be
mostly dry. Then chances for rain/snow will increase Saturday night
into Monday, as a broad trough shifts over the central states.
Temperatures Friday into the weekend will be near to slightly above
average, cooling a bit for early next week.


.AVIATION...(For the 00Z TAFS Through 00Z Thursday Evening)
Issued At 514 PM MDT Wed Mar 21 2018

VFR conditions can be expected today into Thursday for KGCC/KRAP.
Clouds will increase after 10Z, with areas of MVFR/IFR conditions
developing, especially from northwest to south central SD. Patchy
fog could develop overnight across South Dakota plains,
especially in low- lying areas.




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