Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 200819
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
219 AM MDT Fri Jul 20 2018

.DISCUSSION...(Today Through Thursday)
Issued at 219 AM MDT Fri Jul 20 2018

Active NW flow will continue through the period. Weak shortwave
now traversing MT. This impulse is supporting developing elevated
shra/ts over NE WY into far western SD. Expect this activity to
continue through morning in an isolated to widely sct nature,
shifting SE. MUCAPE values remain low AOA 500 J/kg, supporting
very low chances for any severe hail. Meanwhile, backdoor cold
front will continue to slide WSW into the fa at the sfc, keeping
temps at bay today, with mostly 80s expected. An isolated shra/ts
or two will be possible over the central Black Hills this
afternoon given diurnal heating and weak CIN. Any activity is
expected to remain on the Hills. Currently, the forecast is dry
for tonight, however, there is some potential for elevated
convention once again late. LL trough, evident at h7 with a pocket
of high theta-e air will slowly push NE across the BH region in
the presence of a LLJ. Lack of any mid level impulse precludes pop
mention atm. However, convectively generated impulse could
develop over WY this afternoon and possibly force elevated
activity locally tonight. Otherwise, mainly dry wx into Sat before
the next stronger upper trough pushes into the region, supporting
TS chances first over the Black Hill during the day, then over
most of the FA Sat night into Sun with decent coverage. Ample CAPE
and deep layer shear will be present given increasing flow aloft
Sat/Sat night, with a severe threat expected. Flow will then
revert back to NW aloft, with the upper jet wavering over the
region via passing impulses. This will support near daily chances
for TS next week, with cooler but seasonal temps.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Friday Night)
Issued At 1026 PM MDT Thu Jul 19 2018

Isolated TSRA possible overnight from northeast WY into the Black
Hill with brief MVFR vsbys. Otherwise, VFR conditions are
expected through the forecast period.

&&

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

$$

DISCUSSION...JC
AVIATION...Johnson


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