Area Forecast Discussion
Issued by NWS Rapid City, SD

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763
FXUS63 KUNR 252357
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
557 PM MDT Fri May 25 2018

.DISCUSSION...(This Evening Through Friday)
Issued at 153 PM MDT Fri May 25 2018

Western CONUS mean troughing will bring persistent SW flow
through the period. This will support an active pattern as several
impulses eject NE into the Northern Plains. Weak instability over
the BH today will support few shra and TS this afternoon and
evening. Otherwise, upper level ridge will begin to build into the
region tonight through Sat, supporting warm dry weather. Pos
theta-e adv Saturday night might support an E-W band of elevated
convection, esp over NW SD late Sat night. Sfc trough will stall
over the area Sun with a decent upper trough pushing into the
region. Ample LL moisture will advect into the region per SE flow,
supporting CAPE of 1.5-2.5 KJ/KG over NE WY and Western SD.
Increasing shear per advecting jet steak should support a decent
chance of afternoon/evening TS with some severe storms certainly
possible given moisture/CAPE/shear numbers. Sfc boundary will
linger over the area Mon with sufficient flow aloft and ll
moisture certainly in place to support more diurnal shra/TS, some
possible severe once again. Bulk of upper trough will advect
through the region Tues, with another good chance of convection
once again. Drier weather is expected mid next week with weak
ridging in place before another round of western CONUS troughing
develops and supports unsettled flow once again.

As for temps, warm conds expected across the region Sat with 90s
most places. Stalled frontal boundary over the region Sunday will
support cooler conds over NE WY with continued warm SE half. SFC
front will bias further east Monday, with more widespread cooler
conds.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Saturday Evening)
Issued At 557 PM MDT Fri May 25 2018

VFR conditions are expected through Saturday afternoon.

&&

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

$$

DISCUSSION...JC
AVIATION...77



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