Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 170351

Area Forecast Discussion
National Weather Service Sioux Falls SD
1051 PM CDT Wed Aug 16 2017

.SHORT TERM...(This evening through Thursday)
Issued at 317 PM CDT Wed Aug 16 2017

Widespread rain showers with a few embedded thunderstorms continue
to roll over the area this afternoon as mid to upper trough and
associated surface boundary moves northeast into the Upper
Mississippi Valley. Early this afternoon, the IR satellite imagery
showed cooler cloud tops suggesting a weakening/decaying system as
it moves northward, with drier and more stable air starting to surge
behind it.

Hi-res models brings scattered off and on showers continuing through
late this evening. The area of concern this evening will be over
southwest Minnesota, where locally heavy rain could persist bringing
an additional 2 to 3 inches of rain possible through midnight.
Despite a deep rich-moisture, the instability and mid-level lapse
rates are meager, thus only a few embedded thunderstorms could be
possible. Showers and storms will gradually diminish from southwest
to northeast into the overnight hours.

Behind this system, drier conditions return on Thursday as a surface
high pressure builds in. Low to mid clouds will linger through mid-
morning, giving way to a mostly sunny sky in the afternoon. Highs
will be in the 70s along and east of I-29, and in the lower 80s west
of I-29. Overnight lows will range from the mid 50s and 60s.

.LONG TERM...(Thursday night through Wednesday)
Issued at 317 PM CDT Wed Aug 16 2017

A nice compact little wave will drop south through the area on
Thursday night and bring a chance for showers and thunderstorms.
Not thinking anything severe with weak elevated instability.
Looking at a scattered threat. Rainfall amounts should be limited
with a quarter inch or less expected.

An isolated to scattered threat remain along and east of Interstate
29 on Friday as additional jet energy spills in behind the trough of
low pressure. Barring any showers clouds will be on the decrease and
winds will not be very strong so high from the upper 70s to mid 80s
will lead to a nice day.

Friday night into Saturday night will see short wave ridging move
across the central and northern Plains so precipitation is not
anticipated. High pressure at the surface will gradually shift east
and southerly flow will develop ahead of the next wave. Should see
highs in the 80s.

Sunday should also see a good chance at remaining dry with
seasonally mild to warm conditions. Highs will again be in the 80s.

Sunday night into Monday night looks like the next better chance for
showers and thunderstorms. The ECMWF and GFS look the most
reasonable and agree fairly well. This indicates that the low level
jet will focus in or near the area Sunday night into Monday morning
the the boundary will sink south with a continued chance for showers
and storms Monday night. Will need to watch for a severe weather
threat during this time as instability may be supportive but shear
might be a bit lacking.

After this wave moves through cooler air will spill in behind on
Tuesday and Wednesday. Both days should remain dry with lows 55 to
65 and highs 75 to 85.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1047 PM CDT Wed Aug 16 2017

Low clouds and rain will continue will slowly lift northeast
through the early morning hours. Ceilings will hover around the
MVFR and IFR categories in the showers, with some reduction in
visibility at times. Models suggest that conditions will improve
late tonight through Thursday morning as the system lifts away
from the region.




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