Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 170244
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
844 PM MDT Wed Aug 16 2017

.UPDATE...
Issued at 830 PM MDT Wed Aug 16 2017

Upper low lifting into southwestern MN with cloud shield that had
hung over central SD most of the day finally moving eastward,
leaving mostly clear skies over western SD. Some high clouds ahead
of next system moving into northeastern WY. Surface low is
deepening over eastern MT with winds becoming southeast over
northeastern WY and far western SD, which should stay steady
through the night and prevent temperatures from cooling as much as
last night, despite dewpoints in the upper 30s to mid 40s, but
have dropped low temperatures a few degees. Surface trof will
cross forecast area Thursday with some scattered thunderstorms in
the afternoon, mainly over western-central SD as next shortwave
slides eastward.

&&

.DISCUSSION...This Evening Through Wednesday
Issued at 255 PM MDT Wed Aug 16 2017

A warmer and drier airmass will move over the area for the rest
of the week and most of the weekend as near zonal flow develops
over the region. The best chance for showers and storms through
this period will be Thursday afternoon and evening as a shortwave
and surface trough quickly cross the area. With drier airmass
across the area, instability will be relatively weak, with the
threat for severe storms looking to be minimal. However, some
gusty winds will be possible with any stronger storms.
Temperatures over the next few days will be near to above average
after temperatures mostly below average for the last 2+ weeks.

A more active flow is likely to return by the end of the weekend and
early next week. Chances for showers and thunderstorms are forecast
to increase late Sunday and continue into Sunday night as a
shortwave disturbance crosses the area. Another disturbance with
more showers and thunderstorms is progged right now for Monday
afternoon and evening, with some cloud cover possible across at
least parts of the area Monday morning/midday. Model differences are
fairly large at this point, so level of certainty is rather low.

A ridge is expected to build over the Rockies during the middle part
of next week, with at least some slight chances for showers and
storms. Temperatures look to be near average levels for early to mid
week.

&&

.AVIATION...For the 00Z TAFS Through 00Z Thursday Evening
Issued At 524 PM MDT Wed Aug 16 2017

Skies will be mostly clr across the area overnight with a few high
clouds approaching from the west. VFR sct-bkn clouds with sct
tstms will develop Thursday as a trof crosses the area. Winds
will be southeast overnight, then switch to the northwest over
northeastern WY Thursday morning.

&&

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

$$

Update...55
DISCUSSION...26
AVIATION...55



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