Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 171744
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1144 AM MDT Wed Jul 17 2019

.DISCUSSION...(Today Through Tuesday)
Issued at 246 AM MDT Wed Jul 17 2019

08z surface analysis had front from southern MN into southern WY
with low along it over north central NE. Numerous outflow
boundaries zipping around the CWA per surface observations and
1-min satellite imagery. Cluster of strong convection exiting CWA
per regional radar loop/IR. Looking upstream, water vapour showed
upper trough spreading across western MT trailing into western
WY. This feature main concern in the short term.

Today/tonight, upper trough moves into the northern plains. Lead
wave likely to impact CWA in the afternoon and then secondary
wave by early evening. About 2KJ/kg MLCAPE will gel across the
southern half of the CWA by 21z. 40-50kt 0-6km bulk shear present.
CAMs suggest discrete storms by mid-afternoon, especially rooted
near terrain features, and then swiftly move east this evening as
secondary wave scoops activity eastward. Some question as to how
much coverage we`ll have, but a few storms with large hail/damaging
winds seem likely over the slight risk area. Temperatures will be
near guidance with T/Td forecast over Tripp county supportive of
Heat Advisory.

Thursday/Friday, a welcome respite in active weather expected. It`ll
be toasty Thursday given 850-700mb thermal ridge. Might need Heat
Advisory Thursday afternoon/evening for south central South Dakota.

Chances for storms return for the week with cooler temperatures
foreseen.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 1144 AM MDT Wed Jul 17 2019

Isolated to scattered thunderstorm will redevelop by mid to late
afternoon across northeastern Wyoming and far western South
Dakota. Some severe storms will be possible with very gusty winds,
and large hail. LIFR/IFR conditions will be possible in and near
storms. Otherwise, VFR conditions are expected.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory until 8 PM CDT this evening for SDZ049.

WY...None.
&&

$$

DISCUSSION...Helgeson
AVIATION...13



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