Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 131745
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1145 AM MDT Sun May 13 2018

.DISCUSSION...(Today Through Saturday)
Issued at 204 AM MDT Sun May 13 2018

Upper low centered over the Great Basin will continue to support
unsettled SW flow aloft through early this week, with continued LL
moist upslope flow today. Impulses continue to rotate through the
region, with one currently supporting a batch of showers even a
couple TS over the region this morning. This system will mainly
affect the SE third and shift NE through morning. Areas of fog
will continue through morning given light winds and moist BL
flow. Another more subtle impulse will affect the region this
afternoon and evening. This system will mainly bring increased
instability combined with insolation, supporting the development
of sct shra/ts over WY, with additional activity possible over the
Black Hills although instability will be more limited there given
sustained frontal inversion. A little warmer but still cool conds
expected today, with 50s and few 60s expected. Cloud cover and
some higher terrain fog is expected to hang on through much of the
day once again, esp given easterly moist upslope flow. More
organized precip will then be possible across the SE third once
again tonight as the aforementioned impulse lifts NE.

Unsettled SW flow will persist through the remainder week as the
upper western trough gradually breaks down. This will support low
chances for showers through most of the week. Another upper trough
is expected to advect into the western CONUS toward the end of
the work week as a strong northern stream impulse supports a cold
front into the Northern Plains. This looks to favor another cool
weekend, but perhaps not as wet as the current weekend as the
expected western CONUS trough looks to advect out into the plains
and SE of the region rather quickly. The track of this upper
trough (which will be highly influenced by the northern stream
cold front) will dictate how wet and cool the weekend will end up.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Monday)
Issued At 1138 AM MDT Sun May 13 2018

Widespread MVFR/IFR conditions will persist today across much of
western SD, with some MVFR ceilings present across northeast WY.
Conditions should improve to mainly MVFR ceilings across western
SD by early afternoon. Shower activity will mainly be isolated
through the day and into tonight. A thunderstorm or two could
develop in the afternoon and early evening across northeast
Wyoming and the Black Hills. Improvement to mainly VFR conditions
expected overnight with the exception of northeast WY and the
Black Hills where fog/low stratus will re-develop from 09Z Monday
to at least 15Z.

&&

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

$$

DISCUSSION...JC
AVIATION...15



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