Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 221928

Area Forecast Discussion
National Weather Service Sioux Falls SD
228 PM CDT Sat Oct 22 2016

.SHORT TERM...(This evening through Sunday)
Issued at 226 PM CDT Sat Oct 22 2016

Cool front swinging through overnight will keep winds a bit mixed
through the evening and overnight hours. Went ahead and raised lows
a couple of degrees, close to the CONSAll, with the thought that
temperatures might stay up a bit with the wind. Low temperatures
have been dropping below the forecast a bit lately with the drier
ground but banking on winds holding temperatures up. This will lead
into a cooler, but still mild, Sunday with a breezy northwest wind.
Highs will range from 65 to 70 near Sioux City to the upper 50s
along highway 14.

.LONG TERM...(Sunday night through Saturday)
Issued at 226 PM CDT Sat Oct 22 2016

Sunday night and Monday will bring dry weather, with near
seasonable high temperatures Monday despite a very strong upper
ridge, the low levels being too cool to get heated out any warmer,
easily seen on model soundings. A southeasterly surface breeze will
develop and should become a little stronger than loaded model
guidance, mainly west of HON/MHE/PKS where the better heating will
be found. In short, becoming breezy over the southwest corner of the
area from Chamberlain south. High cloud cover will increase from the
west during the day, this evident from high level moisture flowing
over the ridge as depicted on most models.

Tuesday will bring the approach of a southwesterly short wave, and
the development of decent moisture and thermal advection. This will
be the most significant weather affecting the area during the
forecast period. Although dynamic lift will be modest, moisture
levels will increase strongly with H850 dew points rising into the
50s over the Interstate 29 area by late Tuesday. More importantly,
strong theta e advection will develop in two or three stages. The
first ribbon will arrive with favorable winds early Tuesday from the
west southwest, with a second and strong surge arriving by the start
of Tuesday evening from the south southwest, and aided by a weaker
but converging area from the west at about the same time. All of
this will focus rainfall over the eastern half of the area where we
will go with high likely to unqualified rain chances Tuesday
afternoon and evening. For now will accept the modest, 1/3 inch or
so, QPF guidance for Tuesday afternoon with the Canadian model
mostly lacking on rainfall until Tuesday evening. Tuesday night is
still beyond our QPF gridded forecasts, but could see an inch of
rain Tuesday and Tuesday night in southwest Minnesota and possibly
the northern part of northwest Iowa...or if the EC is right,
anywhere in northwest Iowa. Far from producing flood potential, but
a decent soaking. Models, and our forecasts, continue to be fairly
consistent with this system, including timing. The severe storm
threat still appears to be nil.

The system will move out Wednesday, with possible lingering morning
rain east of Interstate 29, then decreasing clouds over the area.
Under upper ridging. temperatures will be modestly mild Thursday and
just a bit warmer Friday. mostly 60s for highs that day. Saturday
should be dry and a bit cooler, although there is a little
temperature uncertainty, with Rockies and southern plains upper
ridging being flattened by short waves flattening the ridge near the
Canadian border. No wintry temperatures yet with this.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1220 PM CDT Sat Oct 22 2016

VFR through the period.




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