062 
FXUS63 KFSD 230852
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
352 AM CDT Sun Jul 23 2017

.SHORT TERM...(Today and Tonight)
Issued at 351 AM CDT Sun Jul 23 2017

Fairly strong upper-level wave pushing into the Great Lakes early 
this morning, with jet digging southward through the Northern 
Plains. Synoptic frontal zone marking stronger surge of cooler and 
drier air has pushed southward into far northern Iowa and southeast 
South Dakota. Ahead of this boundary, moisture lingering near the 
surface and light winds have allowed for some areas of fog, some 
briefly dense, mainly south of highway 3 in northwest Iowa.  As 
front drops southward, this fog is expected to be advected out of 
the area by shortly after sunrise.

Other than the fog, weather concerns will be relatively minor over 
the next 24 hours as cooler high pressure settles through the 
eastern half of the region through tonight.  Likely will be some 
stratocumulus development by early to mid morning which will advect 
through areas east of I-29 through the mid afternoon, perhaps only 
briefly more than a partly cloudy sky. Northerly winds also will mix 
to a refreshing 10 to 20 mph, as dewpoint readings are as much as 10 
to 15 degrees lower than those from Saturday, and temps are near to 
a bit below normal for the date.

Tonight, as ridge of high pressure embraces the eastern portion of 
the plains, may see some additional fog develop mainly from I-29 
eastward late night into early Monday morning. Any fog would likely 
be more focused to lower and wind-protected locations.  Coolest lows 
in nearly a week likely for most, from mid 50s to lower 60s.

.LONG TERM...(Monday through Saturday)
Issued at 351 AM CDT Sun Jul 23 2017

Monday may be a touch breezy, south 10 to 20 mph with gusts around 
25 mph in central SD, as high pressure shifts east. Weak upper level 
ridging will shift east as well with an upper level jet max expected 
to spread through Montana into ND by Monday night. While the GFS is 
producing convection in central SD Monday afternoon/evening none of 
the other models are. A look around at the soundings suggests that 
the drier solution should pan out so will keep the chance for 
thunderstorms less than 15 percent Monday afternoon and evening. 
Monday has the potential to be pretty warm in central SD and will 
aim for highs in the upper 90s. Farther east across southwest MN and 
northwest IA surface high pressure will still influence the air mass 
so much more pleasant highs of 80 to 85 are expected. At this time 
will plan on having all thunderstorm activity north of the area 
through Monday night.

Tuesday afternoon and night still appears to be the best chance for 
a more widespread chance of thunderstorms. Strong upper level winds 
of 95 to 100 knots will move through ND into northern MN during this 
time. At the surface a boundary with a good warming signal ahead of 
it will be found from about south central SD into northeast SD by 
afternoon. Thunderstorms will more than likely develop along this 
boundary and shift east and southeast through the night. Surface 
based CAPE values around 2500 J/kg are likely by late afternoon with 
solid 40 knots of deep layer shear. For now thinking a decent threat 
for severe thunderstorms and will add a mention to the HWO.

The threat for thunderstorms should linger into Wednesday afternoon 
and evening and depending upon how far south the boundary moves a few 
severe storms would be possible. 

Thursday into Saturday for now looking dry and seasonal with highs 
in the 80s and lows 55 to 65. Some hints of stronger warming on 
Saturday but nothing to jump on right now.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 352 AM CDT Sun Jul 23 2017

VFR conditions expected through the TAF period, except for some
areas of IFR fog from extreme northeast NE and southeast SD into
northwest Iowa through 12z.

&&

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

$$

SHORT TERM...Chapman
LONG TERM...08
AVIATION...JM