Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 202048

Area Forecast Discussion
National Weather Service Sioux Falls SD
348 PM CDT Tue Mar 20 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 344 PM CDT Tue Mar 20 2018

Broad band of very light slushy snow and drizzle across northwest
Iowa and Southwest Minnesota will continue to track eastward late
this afternoon, finally exiting the area by mid to late evening.
With temperatures near or slightly above freezing and minor
snowfall rates, this snow will likely be slushy or melt quickly as
it falls, with little additional snowfall amounts expected. Do
not anticipate any icing issues as well, given the relatively
warm air and ground temperatures.

Latest model trends point to a pair of weaker trailing waves
diving through the northern Plains this evening into Wednesday.
The first will pass to our west as it weakens late this
afternoon/early evening, while a second shortwave dives across
east central SD into south central MN late tonight into midday
Wednesday. Neither of these waves should bring much of an impact
to our area with main forcing avoiding the forecast area. Given
the shallow nature of the low level moisture and drier air
arriving at the mid levels, have removed mention of drizzle or
freezing drizzle this evening and tonight.

Stratus will be slow to exit the region, however some
clearing should arrive by midday Wednesday along and west of the
James River, but will likely hold off elsewhere until later
Wednesday afternoon. With low level moisture hanging on tonight,
there will likely be some patchy fog development with ceilings
lowering, especially in the higher terrain. Lows tonight won`t budge
much from current temperatures, with lows in the mid 20s to near 30.
Southerly return flow arrives on Wednesday, which will bring warmer
temperatures to the area. There will be a large gradient across the
area, with the lower 50s near the Missouri Valley where sunshine
will be more ample, while the upper 30s are expected near the
Buffalo ridge where it is likely to be cloudy most of the day.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 344 PM CDT Tue Mar 20 2018

Upper level ridge tracks east across the Great Plains mid week,
with mild temperatures continuing into Thursday. Highs will be in
the 40s and 50s, with near 60 possible near Sioux City.

The active weather pattern makes a return late this week as a pair
of system track into the region. A broad wave lifts across the area
late Thursday night into Friday, with light precipitation spreading
across the area after midnight Friday into Friday morning.
Temperature profiles remain quite tricky overnight, however it looks
like most areas will see primarily a cold rain, however elevated
areas in southwest MN and east central SD could be cold enough for
some light snow. At this time, it looks like the best potential for
precipitation will be south central into east central SD.

A second wave digs across the Four Corners Friday, tracking through
the central Plains on Friday night, with faster timing than seen 24
hours prior. The GFS is the fast of the long range models, bringing
a brief return to upper level ridging by midday Saturday, while the
CMC and ECMWF lag by about 6 hours. Again, temperatures will play a
big role in precipitation type with this system, but similarly to
Thursday night`s wave, the Friday/Friday night system looks to bring
mainly rain, perhaps changing to snow Friday night or Saturday
morning as it exits. Any slight change in track or temperature
profile of course could change the expected precipitation type.

The active weather continues into the start of next week, however
models diverge pretty significantly. Not much confidence in any one
solution, but the pattern supports some chance pops in the forecast
Sunday into Tuesday. Temperatures remain near or just below normals
in the extended forecast.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1210 PM CDT Tue Mar 20 2018

Back edge of the light snow is right along the the I-29 corridor
as of 17z and will continue to taper off from west to east thru
the early afternoon hours across SW MN and NW IA. Chance of some
patchy light drizzle or freezing drizzle mainly to the north and
east of KFSD this evening. Could also see some patchy fog early
Wednesday, but confidence in its extent or impact on a specific
TAF site is too low to include as of now. Otherwise, look for
IFR/MVFR stratus to continue through the overnight hours before
conditions improve through the day on Wednesday.




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