Area Forecast Discussion
Issued by NWS Rapid City, SD

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

FXUS63 KUNR 232021

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
221 PM MDT Wed May 23 2018

.DISCUSSION...(This Evening Through Wednesday)
Issued at 155 PM MDT Wed May 23 2018

Latest analysis shows southwesterly flow aloft over the forecast
area as an upper low/trough approaches from the west. A surface
trough continues to deepen along the eastern slopes of the
Rockies. The resulting southerly low level flow, combined with the
moisture from the rain last night has pushed dewpoints into the
mid-40s to lower 50s over northeastern Wyoming and into the
mid-50s to mid-60s over much of western South Dakota.
Temperatures over much of the area have already reached the
mid-70s over most of the area with mid-80s over parts of south
central South Dakota. SBCAPE ranges from 1000-2000J/KG at this
time with eroding CIN. Shortwave energy moving up from the
southwest has caused showers and thunderstorms to develop over
southeastern Wyoming, which will move into northeastern Wyoming
and southwestern South Dakota during the next few hours. May also
see some convective development over south central SD late this
aftn. With 0-6km bulk shear around 20m/s, there is the usual
hail/wind threat into early evening, becoming more of a wind
threat as an MCS develops and 0-3km shear profiles bulge into the
evening hours. PWATs are relatively high, but storm movement is
decent too. The thunderstorms, and the severe threat will shift
eastward through the evening and are expected to be out of most of
the forecast area shortly after 06Z but may linger over parts of
south central South Dakota into early Thursday morning.

From Thursday into Saturday, an upper ridge will build over the
northern Plains as yet another upper trough dives southward across
the western CONUS. The thermal ridge is trending warmer, with
forecast high temperatures around 20F warmer than average on the
SD Plains. Isolated thunderstorms are possible.

Sunday into Tuesday, the upper trough/low will affect the northern
Plains bringing a period of active weather with good chances for
TS. Mainly dry weather is expected on Wednesday.


.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 155 PM MDT Wed May 23 2018

Scattered showers and thunderstorms will re-develop across
northeast WY and western SD late this afternoon and evening, with
severe storms likely. MVFR to IFR conditions will be possible near
storms, along with gusty, erratic winds.




AVIATION...Pojorlie is the U.S. government's official web portal to all federal, state and local government web resources and services.