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542
FXUS63 KFSD 152338
AFDFSD

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
638 PM CDT Tue Jun 15 2021

.SHORT TERM...(This Evening through Wednesday)
Issued at 236 PM CDT Tue Jun 15 2021

Expect mostly clear skies overnight with a light east or southeast
wind persisting ahead of a sfc trough draped north to south through
the High Plains. As we remain in the drier air north of the front,
temperatures should fall into the 60s across much of the region
overnight. Aided by low level jet forcing along the the mid level
front, the 06z/12z GFS and 00z/12z Canadian support potential for
isolated elevated storms to develop in central or eastern SD after
midnight through Wednesday morning. Since these solutions appear to
be outliers given the weak lift and limited moisture available,
maintained a dry forecast for now. However, if isolated storms are
able to develop despite strong capping, strong to severe
thunderstorms with locally damaging winds or hail are possible
amidst a narrow axis of elevated instability and 0-6 km shear of 30-
50 kts.

Notably warmer weather develops Wednesday as the upper ridge builds
eastward and warm air advection ramps up in southerly flow ahead of
the approaching frontal boundary. In fact, 850mb temperatures rise
to the top 3% of the NAEFS climatology, and afternoon boundary layer
mixing will tap into this warmth. Wednesday will be the hottest day
of the week for much of central and eastern South Dakota, where
closer proximity to the approaching sfc boundary will cause
temperatures to peak near or above 100 degrees Wednesday afternoon.
With dew points in the 60s in this area, heat index values are
likely to reach 100-110 degrees. This supports a Heat Advisory for
afternoon through early evening. Further east, temperatures will be
slightly cooler but still peak near or above 90 degrees.

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 236 PM CDT Tue Jun 15 2021

On Wednesday night, most deterministic guidance supports a shortwave
transversing ridging aloft and prompting a slight chance of
thunderstorms for areas east of I-29. Despite the sfc boundary in
the area and favorable instability and shear profiles for severe
weather, capping and subsidence aloft will make the rain and storm
chances quite low again with guidance trending that shortwave
disturbance further and further east of the forecast area (lee of
the ridge aloft).

Thursday is poised to be the hottest day of the week where warmer
air still resides ahead of the sfc boundary. Across northwest Iowa,
temperatures and heat index values will peak well into the 90s to
near 100 degrees. A chance for showers and thunderstorms lingers
across much of the region on Thursday through the day and evening as
the boundary slowly progresses east. Of heightened interest will be
the afternoon and evening when ridging shifts a bit further east and
a shortwave is poised to spark storms in northern Iowa or
western/southern Minnesota. Big question is whether the better
forcing will slide east out of the forecast area before storms can
develop, but once again, shear and instability profiles are
favorable for severe weather if storms can develop along and east of
I-29.

For Friday through at least early Saturday, drier and slightly
cooler weather is favored behind the departing system as sfc high
pressure slides through. A shortwave trekking through sometime in
Saturday night through Sunday brings the next period of chances of
showers and storms. For those disliking the recent dry and unusually
hot weather, there is good agreement in a pattern shift toward
cooler and wetter weather as an upper trough digs into the Central
U.S.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 637 PM CDT Tue Jun 15 2021

VFR conditions throughout the overnight period into the afternoon
hours tomorrow. Breezy conditions are expected along and west of the
James River valley tonight, with gusts increasing in coverage
tomorrow morning. Widespread gusts will be ranging from 20-25 knots
tomorrow, with a chance for isolated late afternoon thunderstorms
generally along and east of I-29.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory from 1 PM to 8 PM CDT Wednesday for SDZ038-039-050-
     052>054-057>061-063>066-068-069.

MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...BP
LONG TERM...BP
AVIATION...APT