Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 190843

Area Forecast Discussion
National Weather Service Sioux Falls SD
343 AM CDT Thu Apr 19 2018

.SHORT TERM...(Today and Tonight)
Issued at 342 AM CDT Thu Apr 19 2018

Much less active forecast for today/tonight, as surface high
pressure and upper level ridge work across the region. Potential for
patchy fog is really the only concern for sensible weather, mainly
in the James Valley early this morning, and in far eastern portions
of the forecast area late tonight into early Friday. These areas are
most likely to see light winds within the surface ridge, along with
clear skies to optimize radiational cooling.

Temperatures today will be tricky due to lingering snow cover and
limited mixing within the surface ridge, though abundant sunshine
should eat away at widespread snow coverage from recent days. Will
maintain coolest readings for today in areas which received the
heaviest snow with the last couple of systems, but expect highs in
the 40s throughout the forecast area. Lows tonight will be coolest
in the far east, especially the favored low areas around the Iowa
Great Lakes. Readings here could locally dip into the upper teens,
but generally looking for lows around 20 east to near 30 in south
central South Dakota.

.LONG TERM...(Friday through Wednesday)
Issued at 342 AM CDT Thu Apr 19 2018

Strong upper low moves through the Four Corners region tonight into
Friday, then progresses slowly east into the southern/central Plains
and toward the lower Mississippi Valley through the weekend. Leading
wave lifting northward ahead of the upper low along with weak warm
advection should bring increasing clouds into central South Dakota
late tonight, spreading east across the forecast area on Friday. The
moisture increase is largely in the mid-upper levels, as southeast
low level flow out of dominant Great Lakes surface high maintains
fairly deep layer of dry air below 700-750mb, especially across the
eastern CWA. Will continue to carry a chance of light precipitation
into our western areas late Friday into Friday night, with just a
slight chance working into the I-29 corridor and parts of southwest
Minnesota. Influence from this system lessens as we move into the
weekend, with little if any precipitation expected, though clouds
will remain fairly abundant into Saturday. Despite the cloud cover,
high temperatures should gradually warm into the 50s as lingering
snow continues to disappear. More dramatic warming should take place
Sunday/Monday, with temperatures finally climbing to within a few
degrees of seasonal normals, as low level flow becomes more south-

Next system will impact the region early next week, as a northern
stream trough moves out of the Rockies and across the northern
Plains Monday night/Tuesday. Associated cool front will move across
the forecast area Monday night/early Tuesday. While not expected to
return to recent temperature levels, we will see readings drop back
below normal for the end of this forecast period, especially Tuesday
as a chance of light rain will accompany the system across the area.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1043 PM CDT Wed Apr 18 2018

Mainly VFR conditions through the TAF period. Patchy shallow fog
will be possible late tonight through 15z, mainly in low lying
areas along and west of the James River, including HON.




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