Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 231739

Area Forecast Discussion
National Weather Service Sioux Falls SD
1239 PM CDT Tue May 23 2017

.SHORT TERM...(Today and Tonight)
Issued at 411 AM CDT Tue May 23 2017

Large upper low will move southward today along the eastern edge of
the forecast area, with an attendant short wave in an east to west
orientation moving through this morning. At the surface, the winds
will be rather stirred up with a well mixed lowest kilometer, with
mixed layer winds suggesting 15 to 30 mph for the balance of the
day. Scattered showers will be moving southward along the wave,
driven mainly by PVA and a slightly unstable 0-6km lapse rate near
6C/km due to cold air aloft. However, took the mention of thunder
out of the forecast in that it looks not overly unstable enough
anymore to mention it. 0-1km ML cape is very minimal, and MU cape is
all bottled up in the lowest kilometer with virtually none about
900mb. Highs today will be much below seasonal normals, with
readings in the 50s.

The shower activity will wane rapidly this evening as the daytime
heating subsides. Clouds should slowly erode however they could be
stubborn to totally leave along and east of I 29. With a bit of
gradient producing modest wind speeds, lows should stay in the lower
to mid 40s.

.LONG TERM...(Wednesday through Monday)
Issued at 411 AM CDT Tue May 23 2017

Wednesday into Thursday looks to be warmer and mainly dry as surface
high pressure moves through the region and southerly flow returns.
Southerly winds appear to be fairly strong Thursday. There appears
to be a strong elevated mixed layer in the 800-600 mb layer
effectively capping the atmosphere. A weak boundary is expected to
shift through the region late on Thursday and could produce an
outside chance of a storm or two.  Low level moisture and
instability appear to be lacking, along with organized wind shear so
anything that would develop would likely not be severe.

Although a bit breezy north of I-90, Friday looks to be fairly
pleasant with near seasonal highs with variable clouds.

Northwest flow develops through the holiday weekend as slow moving
trough moves into the Great Lakes region.  Each model hits that
there could be a few disturbances roaming through the region through
the weekend, but would be more of a passing shower than a sustained
rain event.  Seasonal temperatures continue through the weekend.

Models really differ by early next week as the EC suggests cooler
air spilling into the Upper Midwest, while the GFS is nearly 10 C
warmer at 850 mb.  GFS ensemble is mainly clustering around the
operational run, so hard to tell at this point which solution is
correct.  Have left the blend for now, which is hedging towards the
warmer GFS solution.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1235 PM CDT Tue May 23 2017

Scattered rain showers will continue this afternoon and evening,
bringing low end VFR to MVFR ceilings. Showers will gradually
diminish tonight, but low clouds/stratus are expected to prevail
into Wednesday morning. This will result in MVFR ceilings through
late Wednesday morning.




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