Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 161046

Area Forecast Discussion
National Weather Service Sioux Falls SD
546 AM CDT Fri Jun 16 2017

.SHORT TERM...(Today and Tonight)
Issued at 512 AM CDT Fri Jun 16 2017

Weak upper level energy will move through northern parts of the area
this morning and bring a small chance for showers. These showers
should not amount to much due to a lack of moisture. These showers
were driven mainly by some very weak instability and convergence
around 700mb. By early to mid afternoon heating of the day coupled
with increasing upper level support may lead to a few showers and
thunderstorms but coverage should be pretty low with CAPE values
likely 500-1000 J/kg or so. The main concern with any thunderstorms
north of a Gregory to about Spencer IA line should be wind with
pretty dry air below 700mb and nicely increasing 500mb to 200mb mid
and upper level jet. In fact winds likely to be about 65 to 75 knots
in that layer by late afternoon.

One area to watch will be from about Yankton to Storm Lake and
south. A nose of potentially enhanced instability will push into
northeast Nebraska which may increase CAPE values to about 2000
J/kg. When coupled with fairly deep, balanced shear and marginal
turning in the lowest km, a few organized severe storms could
develop. One caveat to this is that the nam is a bit of an outlier
on this solution when compared to the HRRR, RAP and GFS. These 3
solutions remain much drier below 800mb than the nam, thus keeping
the deeper instability to the south. Will put a mention of severe
into the far southern CWA but will need to check morning soundings
to determine how much moisture is south that might advect north.

If the stronger storms can develop they should shift south and east
of the area during the evening. The main jet and wave will begin to
spill onto the Plains late tonight and bring a chance for showers
and isolated thunderstorms, especially after about 8z. At this time
none of these storms should be severe.

.LONG TERM...(Saturday through Thursday)
Issued at 512 AM CDT Fri Jun 16 2017

Dirty northwest flow is expected over the weekend as shortwaves
rotate cyclonically around a low pressure system over the great
lakes region.  This will lead to periodic chances for precipitation.
 A cold front is expected to work through the region on Saturday
night, and with 30-35 knots of flow at 925 hpa and decent cold air
advection, we are likely underforecasting wind speeds.

The cooler air will linger across the region on Sunday leading to
cooler temperatures.  Temperatures will warm Monday through Tuesday
as more mild temperatures build in from the west.  Additional
chances for precipitation return to the region on Wednesday and
continue into late week as a series of waves phase and shift east.
The southern most wave is expected to intensify, but there are
question on the trajectory and timing across the plains.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 544 AM CDT Fri Jun 16 2017

Isolated very light showers will be possible this morning then
scattered thunderstorms are expected this afternoon, with the
better chances near KSUX. Outside of the thunderstorms VFR
conditions are expected.




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