Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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611
FXUS63 KFSD 182049
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
349 PM CDT Wed Apr 18 2018

.SHORT TERM...(This evening through Thursday)
Issued at 348 PM CDT Wed Apr 18 2018

Vigorous upper low will continue to exit eastward this evening
through northern Illinois and northern Indiana. On the backside of
this low through the early evening hours, trowaling does exist
across our eastern zones which moves slowly southward. This could
linger some light snow across these areas, with a few flurries,
sprinkles, or even areas of drizzle dotted elsewhere. But overall,
the vast majority of the accumulating snow is over as the mid levels
rapidly dry out ending our deep saturation. Clouds should be on the
decrease overnight tonight. And with winds decreasing and becoming
very light west of I 29, decided to add a mention of fog for those
locations. For lows, blended a lot of bias corrected readings into
the temperatures to give colder values. Looking at a widespread 20
to 25 degrees, again, banking on clearing later tonight. If for some
reason this does not happen, temperatures will be a little warmer.

High pressure will slowly nudge off to the east on Thursday which
will give this area very light winds. With April sunshine, this will
put a serious dent in snow cover due to melting and compaction
despite having highs only in the 40s.

.LONG TERM...(Thursday night through Wednesday)
Issued at 348 PM CDT Wed Apr 18 2018

Thursday night and Friday, closed upper low pressure moves toward
the four corners area with a downstream ridge dominating the plains.
This scenario creates a very large area of high pressure extending
through the MS valley and Great Lakes which will give our area a
persistent, dry easterly fetch of air. Low pops are still warranted
late Friday and Friday night as the upper low moves closer, but the
rainfall will have a hard time reaching locations along and east of
Interstate 29 due to the high to the east. Even in our western
zones, measurable rainfall of more than several hundredths will be
hard to find. The upper low will move through the central and
southern plains this weekend with minimal impact on our area.
Therefore anticipating a warming trend.

Early next week, large low pressure will be situated over central
Canada. Eventually it appears that a short wave will develop on the
southwest side of this low in the northern Rockies, then move across
the northern plains in the Monday night and Tuesday time frames with
the usual timing differences on the deterministic models. Rain is
possible with this wave passage but at least at this time it does
not appear to be snow. That said, we may be too warm on highs on
Tuesday which are projected to be close to normal, especially if
rain does move through.


&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1223 PM CDT Wed Apr 18 2018

MVFR and IFR conditions will gradually improve from northwest to
southeast this afternoon into the evening. Fog will be possible
in the James Valley and points nearby from about 08z through 15z.
Some of this fog could be IFR.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...Winter Weather Advisory until 7 PM CDT this evening for MNZ080-
     081-097-098.

     Winter Storm Warning until 7 PM CDT this evening for MNZ089-090.

IA...Winter Weather Advisory until 7 PM CDT this evening for IAZ001-
     012.

     Winter Storm Warning until 7 PM CDT this evening for IAZ002-003-
     013-014-021-022.

NE...None.
&&

$$

SHORT TERM...MJ
LONG TERM...MJ
AVIATION...08



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