Area Forecast Discussion
Issued by NWS Rapid City, SD

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845
FXUS63 KUNR 301810
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1210 PM MDT TUE AUG 30 2016

.UPDATE...
Issued at 1203 PM MDT Tue Aug 30 2016

Upper ridging continues to dominate the weather pattern across the
Northern Plains. Surface high pressure over North Dakota will
slowly shift southeast, with light east to southeast boundary
layer flow expected across western South Dakota. Mainly dry
conditions are expected across the area. An isolated thunderstorm
will be possible across the Black Hills this afternoon. Short term
convective models are also trying to hint at some storm development
across south central SD late in the afternoon. Will continue to
monitor, and update if development is expected.

&&

.SHORT TERM...(Today Through Wednesday Night)
Issued at 350 AM MDT Tue Aug 30 2016

Upper ridging continues across the High Plains today as the main
flow persists across Canada. Cooler surface high pressure sits
across Manitoba into the upper midwest and ern Dakotas. S/SE return
flow has been increasing overnight and will continue to deepen
today. IR sat shows low clouds developing across the nw/w cntrl SD
plains. Meanwhile fog across the BH has mostly dissipated over the
last hour or two. Low clouds over the plains are expected to
continue through early this morning...mostly dissipating by 15z.
Could see some associated patchy fog develop as well. A dry day is
expected across the plains areas today as the cap remains in place
though weakly. A better chance for storm development will be across
the BH. SBCape is in the 1500-2500 J/KG range...however with the
ridge in place there is extremely weak shear. So any storms that
develop could end up being strong...but likely not long lasting.
Highs today will reach the 80s...and will repeat tomorrow. Upper
ridging will increase in amplitude while remaining stationary across
the region as an upper trough moves into the West Coast. Dry low
levels will keep storms from developing areawide tomorrow. Mostly
sunny skies are expected with breezy S/SE winds.

.LONG TERM...(Thursday Through Monday)
Issued at 350 AM MDT Tue Aug 30 2016

Upper ridge will bring above normal temperatures Thursday and
Friday with rather low chances for precipitation, at least through
Saturday afternoon. Tight pressure gradient Thursday and Friday
will promote breezy/windy southerly winds. At this time, it
appears enough moisture will be present to preclude major fire
weather concerns. As the upper ridge moves east this weekend in
response to upper trough moving across the northern Rockies,
southwest and then west flow will develop bringing increased
chances for showers and thunderstorms. This is a bit slower than
previous long term guidance has depicted.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 1107 AM MDT Tue Aug 30 2016

Isolated thunderstorms are expected over the Black Hills this
afternoon and possibly over parts of south central South Dakota.
Otherwise, VFR conditions will prevail tonight and on Wednesday.


&&

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

$$

Update...15
SHORT TERM...13
LONG TERM...Helgeson
AVIATION...10



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