Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 180903

Area Forecast Discussion
National Weather Service Sioux Falls SD
303 AM CST Wed Jan 18 2017

.SHORT TERM...(Today and Tonight)
Issued at 302 AM CST Wed Jan 18 2017

Still seeing widespread stratus and areas of fog from the Interstate
29 corridor and eastward very early this morning. RH time sections
show these low clouds only slowly eroding from the west into the
afternoon as drier airs filters into the region and the 925 mb flow
becomes more west/southwesterly during the day. Otherwise, a surface
ridge slides quickly across the region, with light northwesterly
winds early transitioning to southwesterly by afternoon. It will
still be a cool day with readings close to or just above normal for
this time of year, with highs generally upper 20s to lower 30s.

Tonight the surface ridge continues to push off to the east, with
light southerly winds and and any remaining clouds clearing out of
the area. In spite of the clear skies and light winds, temperatures
will remain tolerable in an ensuing warm air advection regime, with
lows mid and upper teens.

.LONG TERM...(Thursday through Tuesday)
Issued at 302 AM CST Wed Jan 18 2017

Drab and dreary end to the week looks likely for much of the
forecast area. Abundant moisture below 900mb projected by most
models to expand northward across eastern South Dakota and southern
Minnesota by mid-morning Thursday, gradually thickening to near 875-
850mb by Thursday evening. Subtle lift within the stratus thanks to
weak warm advection could result in some patchy drizzle beginning
Thursday morning. Little change in airmass through Friday, with the
widespread low level moisture and periods of weak lift persisting.
Fortunately appears that temperatures within the stratus and at the
surface will remain above freezing throughout Thursday-Friday, even
Thursday night with raw model consensus pointing to lows holding in
the 34-36 degree range beneath the stratus, so would expect mainly
drizzle with minimal icing potential.

Deeper lift and some increase in mid-level moisture spread into the
area Friday night and Saturday as stronger mid-upper trough swings
northeast across the region. Forecast soundings from both NAM and
GFS maintain an isothermal temperature profile in the lower portions
of the atmosphere, holding at least a degree or two above freezing
below 1500-2000ft. This should limit threat of any freezing precip
types, with cold rain most likely Friday night/Saturday. However, in
areas northwest of Tyndall-Sioux Falls-Marshall line, cannot rule
out some wet snow at times, as this layer cools to within a degree
of the freezing mark.

Lift and associated precip threat move northeast of the area
Saturday night, though lingering troughiness will allow clouds to
hang on into Sunday. Temperatures remain on the mild side of normal
into early next week, with a brief break between systems bringing
some sunshine for Monday.

Another trough begins to move out of the central/southern Rockies
Monday night into Tuesday, spreading clouds and increasing precip
chances back into the region by Tuesday into Wednesday. At this
point, thermal profiles suggest primarily a snow/cold rain potential
with this system, as cooler air aloft settles in before the precip
arrives late Monday night/Tuesday.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1052 PM CST Tue Jan 17 2017

Mainly VFR conditions expected through the TAF period. Models
suggest that some patchy MVFR or IFR fog may redevelop after 06z
for areas along and east of I-29, but will quickly lift late
tonight through around daybreak Wednesday as drier southwest flow
steadily decreases the low level moisture.




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