Preview of NWS' New Version of Forecast
This preview is not operational and should not be used for support decisions.

Area Forecast Discussion (AFD)

Issued by Rapid City, SD (UNR)

FXUS63 KUNR 250436

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1036 PM MDT Sat Aug 24 2019

.DISCUSSION...(This Evening Through Saturday)
Issued at 328 PM MDT Sat Aug 24 2019

Current surface analysis shows weak frontal boundary remaining 
across western SD. Low pressure is located across western SK, with
cold front stretching back into the Pacific NW. Upper level 
analysis shows weakening trough over the western Dakotas into the 
central Plains, with fast zonal flow to the west of the region. 
Skies are variably cloudy, with the most sun across northeast WY. 
Temps range from the 70s to lower 80s across the area, with some 
drier in place across northeast WY into the Black Hills. KUDX 
radar showing a couple of showers and storms over the northern 
Black Hills and some showers/storms wrapping northward into south 
central SD. Southerly winds are breezy across the SD plains. 

Unsettled weather will continue at times across a good portion of 
the area through the rest of the weekend, especially to the east of 
the Black Hills. The best chances for rainfall and storms will come 
later Sunday into Sunday night as the cold front to the northwest 
crosses the region. For late today into tonight, the best chances 
for showers and storms will be east of the frontal boundary, 
especially toward central SD, as trough moves east of the area. A 
strong storm or two is possible late today, but the risk for severe 
storms is low as instability and shear are progged to be marginal at 
best. Temps will drop to the upper 50s and lower 60s in most areas 
by early Sunday. 

Sunday will start off relatively nice, with just a chance for a few 
showers across northwest SD in the morning. Highs will mostly be in 
the upper 70s and 80s, with the higher humidities to the east of the 
Black Hills. More active wx will likely develop later in the 
afternoon into the evening, especially for areas north and east of 
the Black Hills, as the cold front and upper level shortwave slowly 
moves into the area. Frontal boundary will remain to the east of the 
Black Hills, with the best instability east of the Black Hills into 
central SD, 1000 to 2000 j/kg MUCAPE. Shear will increase as the 
front approaches. Isolated supercells could develop later in the 
afternoon into early evening, especially from northwest into central 
SD, with a stronger storm or two also possible in the Black Hills 
area. Chances for severe storms drop greatly to the west into 
northeast WY. However, widespread chances for showers and storms can 
be expected Sunday night as the front moves through the area. 

The front will usher in cooler conditions for much of next week, 
with highs in the upper 60s and 70s across the Plains, 60s over the 
Black Hills. Northwest flow develops behind the trough as it 
strengthens to the northeast of the region. This will bring at least 
breezy conditions early in the week during the late morning and 
afternoon hours. The drier flow should keep pcpn chances to a 
minimum for much of next week, but cannot rule a few showers or 
storms will any weak disturbance that may slide through the area, 
especially late week.  


.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1033 PM MDT Sat Aug 24 2019

During the rest of the night and into Sunday morning, there is a
chance of showers, and possibly a thunderstorm over far
northeastern Wyoming and northwestern South Dakota local MVFR
conditions are possible over those areas. There is also a chance 
of showers over parts of south central South Dakota. Areas of IFR 
CIGS are expected over that area. There is a better chance of 
showers and thunderstorms on Sunday afternoon over parts of 
western South Dakota.