Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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926
FXUS63 KFSD 290811
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
311 AM CDT MON AUG 29 2016

.SHORT TERM...(Today and Tonight)
Issued at 306 AM CDT Mon Aug 29 2016

Current surface obs indicating a cold front extending from north
central to west central SD very early this morning. This boundary
will slide slowly southward through today, becoming situated just
north of the Highway 14 corridor by late afternoon, bringing a small
threat of thunderstorm development over that area after 21z. Other
than some low level convergence with this feature, there is little
in the way of forcing, so still think that low pops are warranted.
Farther to the south, a vort lobe stretching across Nebraska could
induce thunderstorm development there by afternoon with heating, and
some models suggesting that some of this activity could scrape our
far southern zones from Sioux City to Storm Lake during the day.
Again, looking at a low chance of this. It will be another very warm
and humid day with highs in the lower 80s east of Interstate 29 to
near 90 through the James River Valley and south central SD - this
in conjunction with afternoon dew points in the mid 60s to near 70.

Tonight the frontal boundary settles southward, becoming situated
through the southern portions of our CWA by 12z on Tuesday. Again,
could see some thunderstorm development in the vicinity of the
boundary overnight, though models having their usual differences on
how this plays out and the extent of convective coverage. Still weak
forcing with the system, so think that any thunderstorm development
will be spotty to widely scattered. In terms of severe potential for
today and tonight, think the probability is pretty low. While there
is some instability, shear is very low with a weak mid level flow.
Overnight lows will be once again be relatively mild , bottoming out
in the lower to mid 60s.


.LONG TERM...(Tuesday through Sunday)
Issued at 306 AM CDT Mon Aug 29 2016

A weak surface boundary and lingering mid-level energy will provide
a focus for scattered thunderstorms on Tuesday morning and again
during Tuesday afternoon/evening.  While instability ahead of the
boundary does increase, shear remains marginal at best.
Nevertheless, do see the support for an isolated pulse severe storm
late in the daytime hours.

Northwesterly mid-level flow will arrive by Wednesday as ridging
over the Rockies increases. Surface high pressure drifting through
the Great Lakes region will bring cooler and very comfortable
conditions to the region from Wednesday through Friday.

The Labor Day holiday weekend is beginning to look unsettled,
especially during the Saturday and Sunday timeframe.  Medium range
models in good agreement bringing a sharp trough into the Western
CONUS by Friday, inducing southwesterly flow aloft over the Central
Plains for the weekend.   A frontal boundary and series of
shortwaves embedded in the flow, will serve as a forcing mechanism
for convection late Saturday into Sunday morning.   Another round of
thunderstorms will be possible on Sunday.  Given the flow pattern
and increase of shear aloft, will need to monitor the amount of
instability that can build ahead of the boundary.  The Labor Day
forecast remains highly dependent on how the preceding days evolve.
At this time, trends favor lower storm risks, but model guidance may
be a bit too fast to clear the front through the area.


&&

.AVIATION...(For the 06Z TAFS through 06Z Monday evening)
Issued at 1140 PM CDT Sun Aug 28 2016

VFR conditions will be prevalent through this TAF period, although a
brief period of MVFR visibility in BR is again possible late tonight
into very early Monday over parts of northwest Iowa including KSUX.
Spotty thunderstorm chances around the region, primarily late Monday
afternoon/evening near KHON and KSUX. However, probability for any
specific point location too low to include mention in TAFs at this
time.


&&

.FSD Watches/Warnings/Advisories...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...JM
LONG TERM...Dux
AVIATION...JH



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