Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 181750
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1150 AM CST Wed Jan 18 2017

.SHORT TERM...(Today and Tonight)
Issued at 506 AM CST Wed Jan 18 2017

Surface high pressure centered over MO very early this morning will
shift off into the OH/TN Valleys by this evening, and with
increasing warm air advection over our area, it is looking to be a
very mild day for this time of year. Warming will be most realized
over completely snow/ice free areas, with highs close to 50 over
south central SD, then 40s through most of the James River Valley
into northwest IA, tapering back to the upper 30s to the north and
east.

By tonight a shortwave begins to lift out of northern KS into
eastern NE with increasing low level moisture out ahead of the
feature. With that, all guidance indicates stratus increasing over
the lower MO River Valley, northwestern IA, and portions of
southwestern MN after 06Z. Related to that, low temperatures for our
eastern areas will occur earlier in the night, with rising
temperatures after 06Z. Lows will range from around 20 through the
northern James River Valley and east central SD, to lower 30s
through the lower MO River corridor into northwest IA.

.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 18Z TAFS through 18Z Thursday afternoon)
Issued at 1150 AM CST Wed Jan 18 2017

Advection of MVFR to IFR stratus will commence from the south
into the KSUX area by around 09z, spreading rapidly north and east
through the early morning. While drizzle chance does not appear
to be significant enough to mention, there should be an increases
chance for MVFR visibilities to develop along with the stratus.

&&

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

$$

SHORT TERM...JM
LONG TERM...JH
AVIATION...Chapman



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