Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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793
FXUS63 KFSD 230500
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1100 PM CST Wed Nov 22 2017

.SHORT TERM...(This evening through Thursday)
Issued at 240 PM CST Wed Nov 22 2017

The northwest flow aloft continues in the short term, leading to
mostly uneventful weather for tonight and Thanksgiving. This evening
will see mid level clouds slowly move off to the east, leading to
clear skies and relatively light winds around 5 mph tonight. Some
hint at fog in the models west of the James River, but most of the
fog in ensemble short term guidance is coming courtesy of the NAM
and related models, which have been having major trouble with low
level moisture lately to say the least. Have nonetheless put in some
patchy fog along the Missouri River reservoirs in our western zones,
where there is still a source of open surface moisture.

Thanksgiving brings a return to southerly flow and partly cloudy
skies. Winds will be about 5 to 15 mph, so not expecting mixing to
be able to fully access the significant warm layer aloft. That being
said, could still end up in the upper 60s around Gregory and
Chamberlain. Winds will continue overnight, so have held lows just
above consensus guidance.

.LONG TERM...(Thursday night through Wednesday)
Issued at 240 PM CST Wed Nov 22 2017

Friday will be very windy courtesy of the cold advection aloft and
the good pressure gradient in the wake of a frontal passage in the
morning. Coupled with expected minimum RH values below 40 percent,
there will be high fire danger as well. Will need to monitor for a
wind advisory as well. Chances for precipitation have trended
northward as forcing and moisture in our CWA remain marginal.

Saturday through Monday look to be uneventful as longwave ridging
takes over. Boosted high temperatures on Sunday and Monday by a few
degrees given the warm temperatures aloft progged in the models and
the consensus blend being held down by a few cold outliers. With a
decent pressure gradient and guidance agreement on wind direction,
boosted winds a bit during this period.

Next thing to watch in the extended is Monday night through
Wednesday night as a large wave breaks off the persistent
troughing over the Gulf of Alaska. Still plenty of spread between
the models and within the ensembles at this time, but there could
be a good chance for our first snow more significant than a
dusting.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1100 PM CST Wed Nov 22 2017

With increase in near surface moisture, may find isolated low-
lying areas with some patchy MVFR fog through the Missouri River
corridor where winds become light late night, but likely
remaining west of KSUX with shift in winds to northwest wind
remaining longer into the night. Otherwise, expect VFR conditions
through 06z Fri. May need to monitor KFSD/KSUX for developing
low-level wind shear after 02z Friday, but is marginal enough at
this time to leave clear of TAFs.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...Ferguson
LONG TERM...Ferguson
AVIATION...Chapman



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