National Weather Service Weather Forecast Office

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

000
FXUS63 KUNR 212005
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
205 PM MDT Sun May 21 2017

.DISCUSSION...(This Evening Through Sunday)
Issued at 204 PM MDT Sun May 21 2017

Upper low over the upper Midwest will continue to support chances
for showers across the region through Monday as another Fujiwara
like impulse will advect into the region tonight into Monday,
supporting a good chance of rain then. Sct showers/ts ongoing
across the region ahead of the lead jet streak. This activity will
trend SE and wane this evening before the next stronger impulse
arrives late tonight and support shower chances through Monday,
best over the northern Black Hills, where some upslope enhancement
will be found. Some thunder will also be possible once again
Monday afternoon. Windy conds can also be expected with 20-30
knots of BL winds progged for a large portion of the region, esp
NE WY. Showers, clouds, and cool thermal fields will support below
normal temps once again with 40s and 50s expected Monday.
Shortwave ridging will ensue Tues, with perhaps a lingering shower
scentral SD. Dry and warmer weather can be expected midweek
before the next round of troughing arrive toward the end of the
work week.

Large scale flow is trending toward blocking by next weekend per
western NOAM sustained ridging, which would stall or support slow
eastward progression of the expected NW CONUS upper trough/closed
low. This would leave the region in unsettled cyclonic flow for
potentially several days akin to GFS and CMC solutions. Hence,
look for a return to cool conds after Thur, with chances for
precip returning to the area. It is quite possible that temps will
verify even cooler than current forecast numbers in this period.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Monday)
Issued At 1104 AM MDT Sun May 21 2017

Mainly VFR conditions are expected through Monday morning,
although scattered showers through the period may result in local
MVFR conditions. Isolated thunderstorms will be possible this
afternoon and evening. Breezy northwest winds this afternoon will
diminish this evening, and then increase again late Monday
morning.

&&

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

$$

DISCUSSION...JC
AVIATION...Pojorlie