Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 122051

Area Forecast Discussion
National Weather Service Sioux Falls SD
351 PM CDT Mon Mar 12 2018

.SHORT TERM...(This evening through Tuesday)
Issued at 347 PM CDT Mon Mar 12 2018

A longwave upper-level ridge over the Western CONUS will keep active
weather out of the near term forecast period. Light north winds have
suppressed today`s high temperatures, as cool Canadian air
filters into the area. A surface high pressure will move in from
the Northwest overnight leading to mostly clear skies and
potential for fog formation. Due to the relatively dry north winds
the incoming airmass is not overly moist; however, the favorable
radiational set-up looks supportive for at least patchy fog for
much of the James River Valley and the Buffalo Ridge. Fog should
dissipate by mid-morning as sunshine helps mix the lowest layers
of the atmosphere.

Tuesday will be another cool day, as weak winds combine with a
shallow cool air mass keep most locations a few degrees shy of
seasonal average high temperatures.

.LONG TERM...(Tuesday night through Monday)
Issued at 347 PM CDT Mon Mar 12 2018

The upper-level ridge will migrate eastward over the high Plains
during the middle of the week, allowing temperatures to warm on
Wednesday. Most locations will be 5 to 10 degrees above average with
mild south and west winds. Places like Marshall, MN on the leeward
side of the Buffalo Ridge will be breezy with downslope enhancement
of southwest winds gusting around 20-30 mph. Thursday temperatures
will cool down slightly as the pressure gradient switches winds
to northerly and easterly, again bringing in cooler air.

Thursday night looks like the next chance for precipitation as the
pattern becomes more active. A shortwave trough could break off from
the larger amplitude Western U.S. trough and migrate beneath the
ridge. This would cause a rain and snow mix along the Missouri
River, but chances at this time look low given model spread. It`s
also worth noting that previous forecast runs looked noticeably
different, further lowering confidence. This low confidence trend
continues into Friday, as the ECMWF shows a more consolidated low
move south of the region, while the GFS builds another ridge with
dry conditions. Model differences compound over the weekend, so
the current forecast is an equal blend of guidance, showing only
slight chances for precipitation.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1259 PM CDT Mon Mar 12 2018

Light winds and mostly clear skies are expected over the next 24
hours. During the early morning hours Tuesday, patchy fog
development is likely, and in the James River Valley including
KHON, fog could become more widespread. Where fog does become
established, light winds tomorrow morning will cause it to linger
through mid-morning, before enhanced daytime mixing is able to
dry out the lower atmosphere.




SHORT TERM...VandenBoogart
LONG TERM...VandenBoogart
AVIATION...VandenBoogart is the U.S. government's official web portal to all federal, state and local government web resources and services.