Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 211714

Area Forecast Discussion
National Weather Service Sioux Falls SD
1214 PM CDT Fri Oct 21 2016

.SHORT TERM...(Today and Tonight)
Issued at 313 AM CDT Fri Oct 21 2016

Not much going today other than the high clouds and the warming
temperatures. Shortwave ridge will build into the area today, but
it will be dirty to begin with due to high clouds. Warm air
advection and an upper level jet will bring some higher level
clouds over the area, which can already be seen on the satellite.
Highs will be warmer today than yesterday despite the high level
clouds. Raised the highs a little in southwest Minnesota due to
favorable downsloping winds off the Buffalo Ridge which will add a
few degrees to the temps.

Low temps will be the only tricky part of tonight`s forecast as
winds drop off & skies clear. I would expect the temps to fall as
well but not as low as they currently are doing.  Went basically
with the seasonal norms for low temps.

.LONG TERM...(Saturday through Thursday)
Issued at 313 AM CDT Fri Oct 21 2016

Looks like a nice weekend weather wise shaping up, albeit breezy at
times. But the temperatures will be seasonably pleasant with no
chance for precip. A south to southeast flow of air will be found on
Saturday helping to push temperatures upward into the mid 60s to
lower 70s. Then the surface winds will begin to veer to the
northwest Saturday night behind a very weak cold front, ushered
through by a mid level short wave maximized near 700mb passing
across the Dakotas and Minnesota. At this time, the GFS, NAM and
ECMWF all keep the threat for post frontal stratus north of the
forecast area. This makes sense as the wave itself is not diving
very far southward. But it is a bit bothersome as it seems like
we have had no trouble draining stratus further southward then
forecast behind these frontal passages this month. So will watch for
it in future forecasts, but right now Sunday looks mainly sunny with
a high degree of mixing giving highs mostly in the 60s. Boosted the
northwest winds some on Sunday as the depth of mixing is close to
850mb. For Sunday night, with chilly high pressure moving
southeastward across the northern plains, lowered lows by using bias
corrected raw model values when compared to the superblend, noting
clear or mostly clear skies, a dry flow and light winds.

The next item to watch is a strong short wave trough forming mid
week next week and moving eastward across the plains. There will
likely be some warm air advection showers and isolated thunderstorms
dotted around the area late Monday night and Tuesday ahead of the
short wave. The 850-700mb thetae advection is very strong in that
time frame as it moves slowly eastward, coupled with an increasing
moisture profile beginning 06Z Tuesday. Still did not want to go
predominant thunder, as the instability both just above the surface
and aloft is not overly impressive, both in terms of MU CAPE values
and elevated best lifted index values. But there certainly is
enough weak instability that there could be some embedded TSRA mixed
with the showers late Monday night and Tuesday. Then the various
deterministic medium range models including the GFS, ECMWF and GEM
Global are now actually quite similar with the wave passage Tuesday
night and Wednesday. Likely pops are warranted for many of our
eastern zones along with the same instability issues causing some
embedded TSRA with the showers Tuesday night, with some lingering
showers behind the low on Wednesday. The surface low is forecast to
track across areas south of our forecast area. But besides this
track, the thermal profile looks too warm for snow chances at this
time across this forecast area.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1214 PM CDT Fri Oct 21 2016

VFR through the period.




SHORT TERM...Heitkamp
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