Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 261939

National Weather Service Sioux Falls SD
239 PM CDT Tue May 26 2020

.SHORT TERM...(This Evening through Wednesday)
Issued at 236 PM CDT Tue May 26 2020

Vorticity maxima lifting northward out of southwestern Iowa has
assisted in developing convection across much of central Iowa at
mid- afternoon. Further northwest, light rain persists along I-29
and areas further east into Minnesota and Iowa. We`ll be keeping a
close eye on an inverted trough beginning to form just southeast
of the forecast area. Latest observations support this trough
residing just east of Storm Lake, with model guidance indicating
this front may stall along the far eastern tier of counties by
mid-late afternoon. MLCAPE values east of this boundary may climb
up towards 1000 J/KG, with enhancement in 0-1 helicity along the
boundary. While shortwave energy will favor pushing convection
further more north and east during the afternoon, it`s not
inconceivable to have a storm to two drift further west and
interact with this boundary. While the overall severe weather
risks remains on the lower end, the greatest threat would come
from a brief tornado and marginal hail. The greatest risk
timeframe would be from 3pm to 5pm.

Tonight: Most of the area remains dry tonight, outside of a narrow
corridor where lingering showers may persist along a Storm Lake
to Spencer line into the overnight hours. Light winds may lead to
minor fog development further west, but this may be tempered by
increasing cirrus.

Wednesday: Wednesday again should remain dry as the forecast area
remains stuck between in the weak flow between a stronger northern
stream jet over the Canadian border and the upper low across
Arkansas.   Latest guidance continues to hint that weak surface
convergence will stay southeast of the forecast area and this should
keep any meaning shower chance out of the forecast area.

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 236 PM CDT Tue May 26 2020

Thursday: More dominate northerly flow aloft will nudge southward
early Thursday morning. A few lingering showers may move into the
Missouri River valley Thursday morning but are expected to weaken
and diminish after daybreak. Temperatures Thursday will climb into
the lower 70s.

Friday: High pressure moving through the region, along with a
prevailing northwesterly flow at the low and mid-lvls will keep dry
conditions around for Friday. Temperatures remain in the 70s.

Saturday: GFS/EC both rather consistent on a subtle shortwave moving
southeast early Saturday morning.  Warm advection induced by this
shortwave will produce showers and perhaps even isolated
thunderstorms through the Missouri River valley. Northerly winds
through the day will keep high temperatures on the cool side again,
with highs stuck in the 60s.

Sunday-Tuesday: Mid-lvl heights begin to rise quickly on Sunday and
into next week, which should signal a rise to above normal
temperatures for much of the region as we finish May and start June.
Confidence increased for this pattern shift, as no strong blocking
is expected to develop to prevent heights from rising further east
in the CONUS. Highs will rise into the 80s into the middle of next


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1207 PM CDT Tue May 26 2020

MVFR to locally IFR conditions will persist into the afternoon
hours along and east of I-29. Further west towards the James and
Missouri River valley regions, VFR conditions have broken out.

Scattered showers and isolated thunderstorms develop this
afternoon along and east of I-29. The greatest risk of any
concentrated thunderstorm activity will be along and east of
Highway 60. We should see ceiling improvement across the area into
this evening. Light winds could result in minor fog development.




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