Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 192028

Area Forecast Discussion
National Weather Service Sioux Falls SD
328 PM CDT Mon Mar 19 2018

.SHORT TERM...(This evening through Tuesday)
Issued at 327 PM CDT Mon Mar 19 2018

Light precipitation in south central SD will slowly spread eastward
this afternoon and evening, as a minor trough digs eastward across
the northern Plains. Patchy drizzle this afternoon will changing
over to light rainfall this evening, however as temperatures fall
into the lower to mid 30s, rain will change over to light snow. This
change over will occur quickest in south central SD into the highway
14 corridor, including the Buffalo Ridge area. The entire forecast
area will switch to primarily snowfall by late this evening or the
early morning hours. Light snow will continue to slowly track east
across the region into Tuesday, exiting areas west of I-29 by
midday, and northwest Iowa and southwest Minnesota by late

Without a great deal of lift or forcing seen with this system,
precipitation will remain on the light side, however the relatively
long duration of this event will lead to a widespread 1 to 3 inches
of accumulations. With temperatures falling into upper 20s to lower
30s, snow ratios will not be particularly high. The highest amounts
are expected in the higher terrain of the Buffalo Ridge, where
around 3 or locally 4 inches will be possible. Fortunately, forecast
soundings do not support freezing rain or sleet, so icing concerns
are minimal. Northerly winds will also be light for the duration for
this event.

.LONG TERM...(Tuesday night through Monday)
Issued at 327 PM CDT Mon Mar 19 2018

A weak trailing shortwave follows closely behind, diving across east
central SD and southwest MN Tuesday night. This wave weakens as it
arrives, with the lower level moisture holding on. Not seeing much
of any saturation in the dendritic growth zone, so expect
precipitation to be drizzle or freezing drizzle for areas mainly
north of I-90. This activity will be light and very spotty, so do
not expect any icing concerns.

Stratus begins clearing from southwest to northeast Wednesday and
Wednesday evening as upper level ridging builds across the Plains.
Temperatures will once again be on warming trend Wednesday and
Thursday, reaching the mid 40s to mid 50s Thursday.

The active weather pattern makes a return late this week. An initial
wave lifts across the area late Thursday night into Friday, bringing
primarily a cold rain to region. Temperatures are a little more
questionable in southwest MN and east central SD, where there will
be a greater potential for seeing snowfall, but this will be
dependent on the timing of the precipitation, and whether it will
hold off in this area until later Friday. Main wave digs across the
Four Corners region Friday night, tracking through the central
Plains on Saturday. Models are coming into somewhat better agreement
in this feature, with the ECMWF trending more similar to the GFS
with a colder pattern. With clouds and precipitation spreading
across the area, went ahead and lowered highs on Saturday into the
upper 30s to upper 40s, with temperatures likely to struggle to warm
through the day. Still a lot of uncertainty with this system, with
temperatures likely to be near freezing. Any slight change in
track and temperature profiles will result in a primarily rain
event or snow event.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1256 PM CDT Mon Mar 19 2018

Drier trajectory in the lower levels on northeast flow has pushed
the MVFR and IFR ceilings back to the James River valley and
westward at midday, but gradual encroachment of upper trough with
development of light precipitation will again lower ceilings from
the west, as well as some potential for diurnal redevelopment of
scattered to broken MVFR cloud heights. Will see band of mainly
snowfall by evening spreading eastward overnight, and will likely
get period of IFR or briefly lower ceilings and visibilities as
this band of snowfall works through the TAF sites. Lingering
inverted trough through midday Tuesday will keep winds light, but
ceilings largely in the IFR range east of the James River.




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