Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 231809

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1209 PM MDT Sat Sep 23 2017

.DISCUSSION...(Today Through Friday)
Issued at 221 AM MDT Sat Sep 23 2017

Water vapor imagery shows deep upper trof across the western
CONUS with southwest flow across the Rockies into the northern
plains. Scattered thunderstorms continue across south central
South Dakota with area of showers across the Black Hills into
northwest South Dakota. Models in decent agreement through Monday
with timing/placement of precipitation across the forecast area.

For today, shower/thunderstorm coverage will diminish this morning
as initial impulse lifts north of the area. Next shortwave lifts
out of the Rockies this afternoon/tonight. WAA/850-700mb theta-E
advection spreads across western South Dakota resulting in
widespread precipitation. With steep lapse rates, embedded
thunderstorms expected across southwest/south central South
Dakota. Highs 15-20F below average today. Temperatures marginally
cold enough late tonight for rain/snow mix in the higher
elevations of Black Hills.

Upper trof lifts into the northern plains Sunday-Sunday night
with cool temperatures and showers continuing. Temperatures aloft
a few degrees cooler Sunday night for better chance of snow in
the higher elevations of the Black Hills. Upper trof slide east of
the area Monday-Tuesday...with drier northwest flow across the
forecast area. A slow warmup in temperatures, with temperatures
still below average through mid week.


.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 1159 AM MDT Sat Sep 23 2017

Look for IFR and low MVFR conds for the KRAP and KGCC terminals.
Ceilings from OVC005 to OVC008 will be common across the
region...with isolated lower cigs in the higher elevations of the
Black Hills. Vsbys will lower as areas of -ra move in from the
south prior to 24/0000z.




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