Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 182127

Area Forecast Discussion
National Weather Service Sioux Falls SD
327 PM CST Thu Jan 18 2018

.SHORT TERM...(This evening through Saturday night)
Issued at 325 PM CST Thu Jan 18 2018

There appears to be a fair amount of high clouds across the area
tonight.  This will impact radiational cooling some.  NAM suggests
the potential for low clouds and fog tonight, but low level moisture
should remain somewhat limited and have left mention out for now.

Friday into Saturday looks unseasonably warm.  With west to
southwest flow, expect temperatures to warm into the 50s south of
I-90 on Friday. Weak cold front drops through the area Friday
night knocking temperatures back a few degrees. Should still be
above normal on Saturday with relatively light winds.

.LONG TERM...(Sunday through Thursday)
Issued at 325 PM CST Thu Jan 18 2018

Interesting forecast as we head into Sunday. Strong southerly winds
originating in the Gulf region will advect low level moisture
northward in the central and northern plains.  Could see some light
snow associated with the mid level front across the northern half
of the forecast area. Further to the south, the depth of
saturation is confined to the near surface layer leading to the
potential for drizzle/freezing drizzle. As the day moves on,
strong potential vorticity wave moves into the Central Plains.
Mid- level frontogenesis increases across the forecast area. This
forcing is coupled with increasing jet dynamics as the left exit
region noses into the central plains as jet streak migrates from
the base of the trough to the leading edge of the upper trough.

The American solutions (NAM/GFS) are very similar in terms of
location and timing of the system, while 00Z ECMWF lagged 6-12
hours.  The 12Z ECMWF has trended closer to the GFS/NAM in timing,
and has shifted further to the north. The net result is the forecast
area looks to be significantly impacted by the southern stream storm
system. Have raised winds and pops with the system.  With 35-40
knots at 925 mb Sunday night into Monday, potential for near
blizzard conditions exist.

Behind this system...not much in the way of push of colder air with
925 temps remaining in the single digits below zero.  The GFS has a
small weak wave dropping down in northwest flow late on Tuesday, but
this is not supported by the other solutions.  For now, have limited
pops to slight chance.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1044 AM CST Thu Jan 18 2018

High-level clouds will be numerous across the area with VFR
conditions through 18z Fri.




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