National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

421
FXUS63 KUNR 180431
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1031 PM MDT Fri Aug 17 2018

.DISCUSSION...This Evening Through Friday
Issued at 239 PM MDT Fri Aug 17 2018

Water vapor satellite shows a distinct compact shortwave over
northeastern WY moving into western SD. With CAPE values around
1000 j/kg coupled with surface trof from MT into CO providing
surface convergence, some thunderstorms may develop this
afternoon and early evening. Strong storm system moves from
Rockies tonight into the northern Plains Saturday morning, with
thunderstorms spreading eastward through the day and showers
continuing Sunday behind the cold front. With preciptable water
values 1.00-1.75 inches, heavy rain is possible. Temperatures
will be below normal and with cloud cover and north winds, may be
cooler than current forecast. Showers should clear the area Monday
morning as trof moves to the east and upper ridge builds through
the first part of next week. Another wave breaks down the ridge on
Thursday with a chance of storms.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Saturday Night)
Issued At 1031 PM MDT Fri Aug 17 2018

VFR conditions are expected through the remainder of the overnight
period. TSRA will develop from west to east across the area
beginning mid-morning, which could lead to localized MVFR/IFR
conditions. After the initial batch of TSRA crosses the area, a
brief dry period may be possible before widespread -SHRA develop.
These SHRA could be accompanied by MVFR/IFR cigs Saturday
evening/night. Gusty northwest winds will also be possible behind
a cold front Saturday afternoon through the evening, particularly
across the SD plains.

&&

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

$$

DISCUSSION...55
AVIATION...Sherburn