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Area Forecast Discussion (AFD)

Issued by Sioux Falls, SD (FSD)

FXUS63 KFSD 160817

Area Forecast Discussion
National Weather Service Sioux Falls SD
317 AM CDT Mon Jul 16 2018

.SHORT TERM...(Today and Tonight)
Issued at 313 AM CDT Mon Jul 16 2018

A great Monday is ahead with surface high pressure building in over 
the CWA. This will lead to calm winds, mostly clear skies, and 
temperatures a shade below climatological normals. Jet streak 
centered over northeastern IA will put us under the right entrance 
region, so we may actually experience the slightest bit of ascent to 
go with little in the way of mixing, so have leaned slightly on the 
cooler side of consensus guidance. The best ascent will reside to
the southwest of our CWA, so have carried a slight chance for 
showers and storms in our southwestern zones late this afternoon 
and this evening. Instability and shear are lacking in our CWA, 
so not expecting any organized convection.

.LONG TERM...(Tuesday through Sunday)
Issued at 313 AM CDT Mon Jul 16 2018

After an uneventful Tuesday, guidance agrees on a potent wave 
translating eastward across the northern plains Wednesday. 
Southerly flow ahead of this feature will push moisture upward 
once again, leading to likely showers and thunderstorms across the
region. While severe weather threat looks to be marginal given 
progged pre-convective shear profiles, heavy rain may be an issue
given the moisture. Additionally, the wave's eastward progression
looks to slow down while the wave itself amplifies, forcing a jet
streak to ride the top of a ridge over the southwestern CONUS, 
allowing forcing for ascent over our CWA to linger into Thursday 
morning. Have tweaked QPF values up accordingly and may need to go
higher in future updates.

Northwest flow aloft will be in place Thursday and Friday, so have 
kept spotty small chances of precipitation in the forecast. Ridging 
aloft builds in for Saturday, so have eliminated any small chances 
of precipitation that Superblend generated and tweaked temperatures 
upward slightly.

Closed upper low approaches from the northwest by the end of the 
extended period, so mentionable chances of precipitation are 
warranted once again. Still plenty of disagreement amongst 
operational guidance and GEFS members as to the exact evolution of
this feature, so tough to focus on any single period for the 
highest PoPs at this time.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1124 PM CDT Sun Jul 15 2018

VFR conditions are expected to dominate through the period with
relatively light winds and mostly clear skies Monday. Can't
completely rule out some patchy river valley fog early Monday 
morning around KSUX but confidence is much too low to include 




SHORT TERM...Ferguson
LONG TERM...Ferguson