Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 181732
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1132 AM MDT WED MAY 18 2016

.SHORT TERM...Today Through Thursday Night
Issued at 304 AM MDT Wed May 18 2016

Small short wave over southern Canada coming into northern ND is
breaking down the upper ridge, and northwest flow will keep
moisture from upper low over southern AZ from reaching the
forecast area. Surface high has moved into MN while lee trof
develops over MT, increasing southerly pressure gradient over the
forecast area.

Ridge rebuilds today was next upper trof digs along the Pacific
Coast. Temperatures will be warmer as thermal ridge extends over
the Rockies and southerly winds give us warm advection. Low
humidity and sunny skies will also help to raise temperatures.
Very weak instability develops over the Black Hills this
afternoon, but expect only some cu.

A weak short wave crosses the forecast area Thursday afternoon as
surface trof approaches. Increasing low level moisture will lead
to .5-1K J/kg CAPE values over the Black Hills--sufficient for
afternoon thunderstorm development. Cap will limit storms ability
to continue east of the Hills during the evening, but isolated
storms may develop over far southern into central SD as 30-40kt
low level jet increases after midnight.

.LONG TERM...(Friday Through Tuesday)
Issued at 304 AM MDT Wed May 18 2016

Upper low settles over the Pacific NW and stalls out
late in the week, with ridging over the plains. Still can`t rule out
a few showers and thunderstorms over the Black Hills and northeast
WY late Friday if cap erodes enough as southwest flow aloft edges
into the area.

Chances for showers and thunderstorms will gradually increase
through the weekend and into early next week as the upper trough
eventually moves across the Northern Rockies and into the Northern
Plains. Medium range models still having difficulty with timing,
track, and strength of trough as it approaches. Best chances for
pcpn still look to be across western portions of the cwa Saturday,
with more widespread activity likely Sunday into Monday. There is
certainly some potential for strong to severe storms over the
weekend, with perhaps the best chances being Sunday as cold front
slowly passes through the region. Chances for showers and storms
will persist into the middle of next week as another trough likely
develops over the western states. Temperatures will remain above
average through the weekend, with some highs in the 80s across the
plains. More seasonable temperatures should return early next week
behind the front.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 1132 AM MDT Wed May 18 2016

VFR conditions are expected through the forecast period.

&&

.UNR Watches/Warnings/Advisories...
SD...None.
WY...None.
&&

$$

SHORT TERM...55
LONG TERM...26
AVIATION...13



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