Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 221731

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1131 AM MDT Thu Mar 22 2018

.DISCUSSION...(Today Through Wednesday)
Issued at 231 AM MDT Thu Mar 22 2018

An upper ridge building over the region will lead to near or
warmer than average temperatures over most of the forecast area
this afternoon. The exception will be over parts of northwestern
South Dakota were the persistent snow cover has keep temperatures
cooler than average over the previous days.

Mainly dry weather is expected today, however an isolated shower
is possible over parts of northeastern Wyoming late this
afternoon. Breezy southeasterly winds will develop this afternoon
as the surface pressure gradient tightens between high pressure to
the east and a lee side trough deepening to the east of the
northern Rockies in response to the approaching upper trough.

Tonight the upper trough will shift off to the east. A shortwave
trough will approach the forecast area overnight in southwesterly
flow aloft. Lift associated with this trough will bring a good
chance of precipitation to mainly the South Dakota side of the
forecast area tonight. Due to strong low and mid level warm
advection mainly rain is expected. There will however be a chance
of light freezing rain over parts of northwestern South Dakota as
surface temperatures there will fall below the freezing mark.

Chances for rain will continue into Friday as the upper trough
crosses the forecast area. There may be enough instability for
isolated thunderstorms to develop over parts of southwestern into
south central South Dakota on Friday afternoon.

Saturday will be mostly dry as an upper ridge quickly crosses the
region. Then chances for rain/snow will increase Saturday night
into Monday, as a broad upper 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 18Z TAFS Through 18Z Friday)
Issued At 1129 AM MDT Thu Mar 22 2018

VFR conditions can be expected today, with breezy SSE winds
developing later this afternoon. Clouds will increase, with CIGS
lowering toward this evening. Rain will develop, especially north
and east of the Black Hills. Some mixed precip is possible across
northwest SD late tonight. Areas of MVFR/IFR conditions can be
expected. Some gradual improvement to flight conditions is
expected during the day Friday.




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