Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 271712

Area Forecast Discussion
National Weather Service Sioux Falls SD
1212 PM CDT Thu Oct 27 2016

.SHORT TERM...(Today and Tonight)
Issued at 328 AM CDT Thu Oct 27 2016

The main forecast concern today will be the extent of the stratus
deck and how this will impact temperatures. Winds remain light this
morning, posing the threat for fog, however cirrus clouds streaming
across the region have prevented fog from becoming widespread.
Patchy fog or areas of fog will remain possible through a little
after daybreak. The low stratus has eroded overnight across much of
the region. Much of southwest Minnesota into the Iowa Great Lakes
will see the low stratus linger through the remainder of the
morning, then lift in the afternoon as southerly winds increase.
With clouds lingering into the afternoon in this area, did lower
highs by several degrees.

Elsewhere, return flow will usher in decent warm air advection with
850 mb temperatures peaking in around 15 to 18C in south central SD
into the I-29 corridor. Cirrus clouds will also shift east this
afternoon with upper level ridge axis arriving, allowing a great
deal of afternoon sunshine in our west. As a result, expect a large
range in temperatures across the forecast area. Highs will range
from the upper 50s near the Buffalo Ridge, to the mid/upper 70s in
south central SD.

Southerly winds continue overnight at around 10 to 15 mph, limiting
any threat of fog. Expect a seasonally mild night with temperatures
near 50 to 55 degrees.

.LONG TERM...(Friday through Wednesday)
Issued at 328 AM CDT Thu Oct 27 2016

Upper level ridge over the central CONUS begins to flatten out on
Friday, and with strong warm air advection out ahead of an
approaching surface trough temperatures will climb to much above
normal for this time of year. Highs will be approaching 80 degrees
through south central SD, tapering back to the lower to mid 70s
along the I-29 corridor and eastward. A surface boundary slides
across the area during the day, with breezy southwesterly winds
transitioning to northwesterly and diminishing by later in the
afternoon. With temperatures closing in on 80 and relative humidity
values just under 30 percent, there will probably be an enhanced
fire danger over south central SD in the afternoon, however the
saving grace will probably be the fact that winds will actually
become lighter over that area by afternoon.

With the passage of the aforementioned boundary, cold air advection
will begin to be realized on Friday night, though temperatures will
still remain mild with clouds increasing overnight. Looking at lows
in the mid and upper 40s.

Models still pegging a weak shortwave sliding across the area on
Saturday, bringing the possibility of scattered showers, mainly from
the I-90 corridor northward. With continuing cold air advection and
cloud cover, it will be a much cooler day with highs mostly 50s -
with some 60s possible through the Sioux City to Storm Lake corridor.

After subtle warming on Sunday, more significant warming will be
realized on Monday in a southwesterly flow out ahead of a shortwave
ejecting out of the central Rockies. It still appears that for the
most part this energy will drive to the north and west of our area,
thus keeping any rain chances at bay. With the passage of this
system more seasonable temperatures will return to the area, with
dry conditions through at least midweek.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1206 PM CDT Thu Oct 27 2016

IFR ceilings slow to erode in the James Valley and Big Sioux
Valley, but both of these locations should see the stratus erode
fully this afternoon, with the Big Sioux the slowest. After this
VFR conditions are expected. The exception may be parts of
northwest Iowa and southwest Minnesota where weak mixing today
could lead towards a redevelopment of fog/stratus but for now
leaning towards not enough coverage to inclulde in the TAF at SUX
or FSD.




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