Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 201028

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
428 AM MDT Fri Apr 20 2018

.DISCUSSION...(Today Through Thursday)
Issued at 350 AM MDT Fri Apr 20 2018

Upper level analysis has broad ridging across the western CONUS
with closed low over southern Utah. Extensive cloud shield is in
place ahead of the low, slowly extending northeast across South
Dakota. Regional radars have some weak echoes across Wyoming,
slowly moving to the north. Temperatures across the area are in
the 30s to lower 40s, with breezy east to southeast winds.

Latest model runs have come in a little slower with eastward
progress of the southwest closed low. Closed upper low will move
across the Four Corners region today, and into central Colorado by
this evening. Rain will begin spreading across southern and
western portions of the CWA by mid morning, with some light snow
possible over the Hills. Better chances for rain will hold off
until the afternoon and evening hours, with best chances from
Interstate 90 south. Some areas across southwestern South Dakota
should see about a tenth to two tenths of moisture with this
system, and 1 to 2 inches of snow will be possible across the
central and southern Black Hills.

Upper low continues its slow trek east on Saturday as broad
ridging remains across the central CONUS. Precip across southern
South Dakota will slowly shift south and east during the day,
eventually ending by late Saturday afternoon. Mostly cloudy skies
and lingering precip will keep temperatures in the 50s for most
locations. Cloud cover may diminish enough across western areas to
see some temps near 60. Brief upper ridging will allow for a warm
and dry remainder of the weekend, with highs warming into the 50s
and 60s on Sunday.

On Monday, a potent shortwave will dive across the Northern
Rockies and approach the Northern Plains. Some weak instability
may allow for a few isolated thunderstorms late Monday into Monday
night. Following this wave, a more benign weather pattern is
expected to bring a mild and fairly dry rest of the week.


.AVIATION...(For the 06Z TAFS Through 06Z Friday Night)
Issued At 1036 PM MDT Thu Apr 19 2018

VFR conditions are now expected to persist area-wide through
approximately 15z Friday.

After 15z, MVFR cigs associated with SHRA will develop over
northeastern WY/southwestern SD, then gradually overspread most of
the area Friday afternoon into the evening. Over higher elevations
of the Black Hills, IFR/LIFR cigs and vsbys are expected in -SHSN.
Occasional IFR/LIFR cigs are also possible in heavier SHRA across
northeast WY and far western SD.

Once MVFR to LIFR conditions develop tomorrow morning/afternoon,
they should hold for the remainder of the TAF period.




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