Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 190333

National Weather Service Sioux Falls SD
1033 PM CDT Thu Apr 18 2019

.SHORT TERM...(This Evening through Friday)
Issued at 242 PM CDT Thu Apr 18 2019

Subtle wave sliding down the back side of departing trough, along
with weak backdoor cool front, keeping spotty showers going across
the region this afternoon. This activity expected to diminish by
shortly after sunset, with mostly clear skies and decreasing winds
through the overnight as surface ridge moves into eastern South
Dakota. Could be some valley fog again in areas which recently lost
or are still working on reducing their snow pack, but do not expect
it to become widespread, as temperatures fall into the lower-mid
30s most areas.

Friday will be the start of our brief warm-up, with plentiful
sunshine and fairly light winds as the surface ridge continues to
drift east into Minnesota and Iowa. Afternoon temperatures will be
close to seasonal normals, with readings topping out in the upper
50s to mid 60s.

.LONG TERM...(Friday Night through Thursday)
Issued at 242 PM CDT Thu Apr 18 2019

First half of the weekend will bring a taste of early summer, with
modest southwesterly flow bringing a wedge of warmer air into the
region for Friday night and Saturday. After a mild night in the 40s,
temperatures on Saturday will warm quickly to our warmest readings
of this young Spring season. Models are consistent showing a strong
thermal ridge ahead of an approaching cool front, with 850mb temps
of 15-20C and 925mb readings 20-25C, or perhaps a touch warmer in
south central South Dakota. With a favorable south-southwest flow in
the mixed layer, these temperatures are conservatively supportive of
highs in the upper 70s-lower 80s, possibly even some mid 80s in our
far southwest. Given some solid agreement among the models, and an
recent cold bias in our highs over those areas which were lacking
snow cover, have bumped blended highs up a few degrees toward the
warmer end of available guidance.

Aforementioned cool front sags southward through the forecast area
Saturday night/Sunday, but without a strong upper wave to push the
cool front south, model consensus hangs the low level boundary up
across northwest Iowa with a mid level boundary a little farther
north. This will allow for a chance of light showers for the latter
half of the Easter weekend as various weak waves slide along these
boundaries. Not looking at full-day washouts or heavy rainfall, but
some spotty light rain showers or sprinkles at times throughout the

Unsettled pattern continues into the first part of the upcoming work
week, though seeing less agreement among the models in the handling
of a trough which digs into the southern Rockies by 12Z Monday. GFS
is by far the wetter of the deterministic model solutions, and has
support from some of its ensemble members. However, just as many
members favor the weaker/dry pattern seen in the CMC/ECMWF models.
With low confidence in the evolution of this feature, did not alter
the low precip chances produced by blended guidance Sunday night
through early Wednesday. Greater confidence that temperatures will
cool off from the warmth of Saturday, with daytime highs generally
within a few degrees either side of normal through the middle of
next week.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1031 PM CDT Thu Apr 18 2019

VFR conditions will dominate through the TAF period. There are
some indications that patchy fog may develop around KHON late
tonight into mid morning on Friday.




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