Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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281
FXUS63 KFSD 230841
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
341 AM CDT Mon Oct 23 2017

.SHORT TERM...(Today and Tonight)
Issued at 340 AM CDT Mon Oct 23 2017

A cold front is presently pushing through the James River Valley
very early this morning and should be through the entire CWA by 13Z.
Otherwise, an upper level trough will deepen over the central CONUS
today, and with cold air advection behind the aforementioned front,
rapid surface pressure rises, and winds increasing to 40 to 50 kts
at the top of the mixed layer, it will be a windy day. Needless to
say, the current Wind Advisory remains valid across the area until
00Z this evening. High temperatures today will run from the mid 50s
to lower 60s, though as a secondary cold push drops into the area
later this afternoon, may see temperatures begin to fall, more so
over east central SD into southwestern MN. Could even have a few
sprinkles/light rain over that area with this surge, though it is
expected to be very isolated.

Winds will drop off just a bit by this evening, though it will still
be breezy. Even so, by later in the night winds will begin to
increase again as the gradient tightens in response to a rapid
intensification of low pressure over the Great Lakes area. They may
in fact start to close in on Advisory criteria in our east later in
the night. Because of that, there may be the possibility of the day
shift having to issue another Advisory after the current one wraps
up. While it will be colder tonight, temperatures will remain in
check with the fairly strong winds. Lows will be mid 30s to around
40.

.LONG TERM...(Tuesday through Sunday)
Issued at 340 AM CDT Mon Oct 23 2017

Winds will continue to strengthen on Tuesday with mixing and mixed
layer winds of 35 to 40 kts, and as mentioned above may again need
some type of Wind Advisory during the day, with the better chance
from the I-29 corridor and eastward. For the first time in quite a
while, temperatures will be below normal with highs upper 40s to mid
50s.

Quite a moderation in store for Wednesday. This in response to an
upper level shortwave ridge sliding across the region and the low
level flow beginning to take on a southerly component as a surface
trough deepens through the western High Plains. Much less windy on
that day, with highs running mid 60s to lower 70s.

The warmup will be short lived however, as the aforementioned
surface trough slides across the region on Wednesday night and an
upper level trough deepens over the Plains. With that, winds will
again pick up late at night, and had to significantly increase wind
speeds over given Superblend values. It appears that Thursday will
again be flirting with Wind Advisory criteria in a strong cold air
advection regime. Temperatures will respond accordingly with highs
in the lower to mid 50s. Models differing somewhat on the track of
the surface low and the upper level energy with the aforementioned
upper level trough, and as a result are producing a differing
outcome in terms of precipitation for our area on Thursday night
into Friday. The ECMWF would suggest a slightly better chance over
the northeastern portions of our CWA during this time frame than the
GFS which keeps features farther to the north. Either way, it looks
to be only a skirting glance for very light precipitation (which
would be in the form of light snow on early Friday morning with
supportive thermal profiles). The coldest portion of this airmass
would reside over our area on Friday, when highs will struggle to
reach 40.

The upper level trough will then continue to have influence on our
weather into next weekend. Temperatures look to remain below normal
with dry conditions prevailing.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1135 PM CDT Sun Oct 22 2017

Strong northwest winds will be the primary aviation concern
through this TAF period. A cold front moves southeast the region
early in the period, followed by a 2-3 hour period of low-level
wind shear, as winds aloft rapidly increase above a surface-based
inversion. By daybreak or shortly thereafter, these strong winds
aloft mix to the surface, with wind gusts nearing 40kt likely in
many areas late morning through sunset. Aside from the winds, VFR
conditions will prevail through the period.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory from 10 AM this morning to 7 PM CDT this evening
     for SDZ038>040-050-052>071.

MN...Wind Advisory from 10 AM this morning to 7 PM CDT this evening
     for MNZ071-072-080-081-089-090-097-098.

IA...Wind Advisory from 10 AM this morning to 7 PM CDT this evening
     for IAZ001>003-012>014-020>022-031-032.

NE...Wind Advisory from 10 AM this morning to 7 PM CDT this evening
     for NEZ013-014.

&&

$$

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



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