Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 260520
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1120 PM MDT Sun Aug 25 2019

.UPDATE...
Issued at 648 PM MDT Sun Aug 25 2019

Next round of convection, with some strong to severe
thunderstorms, is currently crossing northeastern Wyoming. Those
storms are expected to continue across the Black Hills area and
into southwestern and south central South Dakota still this
evening, exiting south central South Dakota after midnight.

&&

.DISCUSSION...(This Evening Through Sunday)
Issued at 240 PM MDT Sun Aug 25 2019

Current surface analysis shows low pressure over western ND, with
cold front extending south into northwest SD and the Black Hills
area. Upper level analysis shows strong jet moving into the area
from the west, with near zonal flow in place. Skies are mostly
sunny to partly cloudy with temps generally in the upper 70s and
80s. KUDX radar still shows a few showers and embedded thunder
over northwest SD, with some activity developing now over the
Black Hills. Winds are northwesterly behind the front, east to
southeast ahead of it.

Active wx is expected across parts of the area late this afternoon
and evening as the cold front and shortwave energy aloft move
further east across the region. Best instability will remain east of
the Black Hills toward central SD, up to 2000 j/kg MUCAPE, with
sufficient shear for supercells late today along and east of the
front. A severe thunderstorm watch has just been issued for far
eastern parts of the forecast area until 03z. Stronger shear further
west behind the front could combine with adequate instability for
strong to marginally severe storms as well from far northeast WY
through the Black Hills area this evening. Large hail, strong wind
gusts, and locally heavy rainfall are possible with the strongest
storms. Trailing upper level energy will continue to bring chances
for showers and storms into the overnight.

Much cooler and brisk conditions can be expected for the first half
of the week as strong northwest flow aloft develops behind
strengthening system to the northeast of the region. Gusty northwest
winds can be expected during the late morning and afternoon hours on
Monday and Tuesday across the SD plains. A few showers are possible
Monday, especially over northwest SD and the Black Hills. Otherwise,
mainly dry conditions for the first half of the week. Highs Monday
and Tuesday will be in the upper 60s and 70s across the plains, with
upper 50s and 60s over the Black Hills. Nighttime lows will drop
into the mid 40s to mid 50s, with some 30s likely over the higher
Black Hills Monday night and Tuesday night. A bit more seasonable
temperatures will return midweek, but temps will generally stay
below average into next weekend. Weak disturbances and another cold
front toward the end of the week could bring a few showers and
storms, but most areas will likely stay dry.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1116 PM MDT Sun Aug 25 2019

Showers and thunderstorms continue to march from west to east
across the area. The strongest storms are along a line from KPIR
to KPHP to just west of KTIF. Strong, erratic winds are expected
in this line of storms as it pushes east. Some lingering showers
and storms over far western SD and NE WY that should slowly move
out of the area. Expect MVFR/IFR with the strongest storms.
Conditions will gradually improve to VFR from west to east late
this morning. VFR conditions will continue Monday with breezy NW
winds across the region.

&&

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

$$

Update...10
DISCUSSION...26
AVIATION...Eagan


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