000
FXUS63 KUNR 202332
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
532 PM MDT Sun Aug 20 2017

.DISCUSSION...(This Evening Through Sunday)
Issued at 256 PM MDT Sun Aug 20 2017

Upper air analysis shows zonal flow across much of the northern
CONUS with a series of weak waves cross the central third of the
country. One of these waves brought showers to parts of northwest SD
earlier the morning. Surface analysis shows high pressure centered
across the Dakotas with mostly sunny skies across the area with
highs in the 70s to low 80s.

An overall quiet evening is expected...with increasing clouds. Short
range models are not agreeing very well with how storms may end up
developing this evening ahead of a very weak wave...though latest
trends show storms popping up across the southern Black Hills/SW SD
area. Good theta e advection will develop tonight as southeast
return flow sets up. Storms will develop ahead of another wave late
tonight over NW SD and push into better theta e air through the
western SD plains into Monday morning...then south central SD late
Monday morning into the early afternoon. Clouds across western SD
will likely be an issue for the eclipse...most most likely closer to
central SD. It`s looking better approaching the Black Hills
area...and into northeast WY. Highs will be in the mid 70s to mid
80s.

Drier weather is expected Tuesday and Wednesday with highs pressure
across the northern plains and upper ridging building over the
northern Rockies. More active weather is expected toward the second
half of the week as the next upper trough approaches from the
northwest CONUS. Temperatures near seasonal averages will continue.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Monday Evening)
Issued At 529 PM MDT Sun Aug 20 2017

Expect isolated/scattered -TSRA to develop this evening and move
east across the area. Local MVFR conditions will occur. VFR
conditions then expected Monday except across south central SD
where MVFR ST is likely.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

DISCUSSION...13
AVIATION...Helgeson