Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 191948

Area Forecast Discussion
National Weather Service Sioux Falls SD
248 PM CDT Sat Aug 19 2017

.SHORT TERM...(This evening through Sunday)
Issued at 248 PM CDT Sat Aug 19 2017

A quiet evening ahead with southerly flow in place. A weak piece of
energy will move through Nebraska and with a fairly strong EML so
would expect isolated to scattered showers and thunderstorms to
develop. Will maintain a small chance south of Interstate 90 from
about 4z through 12z. Not expecting any of this activity to be
severe. While Sunday should remain dry a wave to the north may
collapse the mid level boundary south and enhance the southerly flow
ahead. Not seeing any great signals in the models but enough to
maintain a small chance for thunderstorms east of Interstate 29 in a
small corridor of warm air advection. While severe weather is not
anticipated mid and upper level shear as well as decent CAPE would
support an isolated severe storm.

.LONG TERM...(Sunday night through Saturday)
Issued at 248 PM CDT Sat Aug 19 2017

Sunday night into Monday morning starting to trend downward with
the chances for showers and thunderstorms. Strong capping aloft
looking like a limiting factor for thunderstorm development. Shear
and instability pretty marginal so if anything can develop do not
anticipate a whole lot of problems with severe weather.

Monday into Monday night starting to look like a more favorable time
frame. This likely due to a strong piece of energy aloft expected to
move into western Sd and western Nebraska very late Sunday night
into Monday morning. This should allow for some decent mid level
frontal forcing and could lead to a few elevated thunderstorms to
develop in the morning in south central SD or north central
Nebraska. If this happens there would be a pretty good chance for
additional development through the day which of course would
unfortunately create problems for any eclipse viewing. However, if
morning thunderstorms can be avoided as we start to head towards
peak heating the lull in temperature rise from shortly after noon
until about 2 pm will likely aid in keeping any new thunderstorm
develop later in the afternoon as the environment will need to
recover after temperatures likely fall 5 to 10 degrees under the
shadow of the moon. Regardless, a fairly stout 2500-3000 J/kg CAPE
and fairly nice deep layer shear would likely support some severe
weather. A lot will depend upon the morning potential and the affect
of the eclipse.

After this system move through on Monday night a cooler and mostly
dry Tuesday through Saturday is expected. Overall highs will be in
the 70s and lows will be in the 50s. This will be care of fairly
broad and weakening northwest flow aloft as a deep low pressure to
the northeast continues to shift eastward.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1204 PM CDT Sat Aug 19 2017

Isolated showers and thunderstorms will be possible late tonight
and early Sunday morning south of Interstate 90. Patchy fog will
be possible in parts of northwest IA late tonight as well.
Otherwise VFR conditions are expected.




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