Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 141739
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1239 PM CDT Sat Apr 14 2018

.SHORT TERM...(Today and Tonight)
Issued at 358 AM CDT Sat Apr 14 2018

...Blizzard Conditions Expected Across the Region Today...

As of 08Z Saturday, the WV satellite imagery shows the impressive
strong 500 mb low positioned over central Nebraska, with the warm
conveyor belt continuing to transport moisture over the region. At
the surface, the closed low is located close to the NE/IA/MO/KS
border. This strong system is moving very slowly eastward, therefore
delaying the arrival of heavy snow for areas east of the James
River. The potential for moderate to heavy snow across the entire FA
remains, but have shifted the heaviest snow accumulations a bit to
the east.

Early this morning, moderate to heavy snow began to fall across
south central and east central South Dakota behind of the 700 mb
front. Current radar shows that most of the precipitation located
east of the James River has already mixed with or changed to snow.
Elevated convection associated to favorable dynamics and theta-e
advection continues through early this morning. Therefore, cannot
ruled out isolated thunderstorms and some sleet mixed in, mainly
east of the James River. In fact, thermal profiles suggest some
sleet potential continuing through mid-morning, mainly along and
east of a line from Sioux City to Worthington to Windom area.

Hi-res models suggest moderate to heavy snow spreading across most
of the area by around daybreak, and continue through the day. A
secondary band of snow could develop along and east of a line
from Yankton to Sioux Falls to Marshall by late morning/early
afternoon. With strong DivQ above the frontogenesis and deep
dendritic layer, these areas could see the heaviest snow amounts.

Mid-level frontogenetic forcing and instability/EPV* above will
slowly weaken through the evening from northwest to southeast. Snow
will become light in intensity by late Saturday evening, but light
snow may linger into Sunday.

Strong northerly winds of 25 to 35 mph, gusting as high as 55 mph
continues today. The momentum transfer from modeled soundings
continue to indicate the potential for strong wind gusts of 45-55
mph through Saturday evening. Winds are expected to decrease
Saturday night as the upper wave moves out of the region and
pressure gradient weakens/relaxes. Breezy conditions remains with
sustained winds of 15-20 mph out of the north.

Currently headlines highlight snow and potential blowing snow well
through early Sunday morning. Blizzard warning continues today with
potential of 4 to 8+ inches of snow across the region, higher
amounts to over a foot, possible east of I-29. Snowfall rates of 1-2
inches/hour are expected.

In terms of impacts, snow-covered and slippery roads are expected.
Travel will become difficult if not impossible due to limited
visibility/whiteout conditions throughout the day. Despite
decreasing snowfall rates late in the evening, blowing/drifting snow
could still cause difficult driving conditions through Sunday.

.LONG TERM...(Sunday through Friday)
Issued at 358 AM CDT Sat Apr 14 2018

Did not spend a lot of time on the extended due to ongoing weather.
Behind the strong upper low, cold air pushes south of the CWA
bringing well below normal temperatures for Sunday. A very cold
Sunday morning is anticipated with lows in the teens and low 20s.
Skies will gradually clear from west to east, but with the recent
snowpack and northerly winds highs will only reach the lower 30s.

Dry conditions will persist Sunday into Tuesday as an upper ridge
builds across the Plains ahead of the next system arriving by the
middle of the week. At the moment, it looks to be a shortwave
producing rain and snow, but it does not look to be as strong as
the system that is currently over the region.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1237 PM CDT Sat Apr 14 2018

Very poor conditions expected through the day and into this
evening, with snow and blowing snow due to frequent wind gusts in
excess of 35-40kt. Gradual improvement this afternoon toward the
James River Valley, and after 00Z-03Z along I-29. IFR conditions
will likely persist into Sunday morning for parts of southwest
Minnesota, with MVFR ceilings dominant elsewhere around the area.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Blizzard Warning until 10 PM CDT this evening for SDZ039-040-
     054>056-060>062-065>071.

     Blizzard Warning until 7 PM CDT this evening for SDZ038-050-052-
     053-057>059-063-064.

MN...Blizzard Warning until 10 PM CDT this evening for MNZ071-072-080-
     097-098.

     Blizzard Warning until 1 AM CDT Sunday for MNZ081-089-090.

IA...Blizzard Warning until 10 PM CDT this evening for IAZ001-012-020.

     Blizzard Warning until 1 AM CDT Sunday for IAZ002-003-013-014-
     021-022-031-032.

NE...Blizzard Warning until 10 PM CDT this evening for NEZ013-014.

&&

$$

SHORT TERM...05
LONG TERM...05
AVIATION...JH



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