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335
ACUS03 KWNS 260705
SWODY3
SPC AC 260704

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0204 AM CDT Mon Jun 26 2017

Valid 281200Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
KANSAS NORTHEASTWARD INTO SOUTHERN WISCONSIN...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
HIGH PLAINS NORTHEASTWARD INTO THE UPPER MS VALLEY...

...SUMMARY...
Scattered severe thunderstorms with large hail and damaging winds
are expected mainly from northern Kansas into Iowa, with more
isolated activity stretching from Wisconsin to Colorado. A couple
tornadoes are also possible mainly northeast of the Missouri river,
including Iowa and southern Wisconsin.

...Synopsis...
A progressive, low-amplitude shortwave trough will be located over
the upper MS Valley Wed morning, with a belt of 30-45 kt midlevel
flow extending westward across the Plains. This wave will continue
across the upper Great Lakes during the day, with increasing wind
fields to the west as an upper jet noses into the central High
Plains. At the surface, low pressure with trailing cold front will
move from the eastern Dakotas into MN during the day, and into
northern WI overnight, with front becoming quasi-stationary across
KS. Meanwhile, a warm front will cross the MS river during the
afternoon. To the south of these fronts, a plume of mid 60s F
dewpoints will exist, with perhaps near-70 F dewpoints across the MO
Valley by late afternoon. Aforementioned boundaries, and any outflow
boundaries that may exist, will all play a role in focusing
thunderstorm development.

...Southern MN and WI into KS...
Scattered showers and storms are likely to be ongoing across the
upper MS Valley Wed morning, ahead of the low and in a zone of
low-level warm air advection aided by a 40-50 kt low-level jet. This
activity may not be severe due to weak instability initially.
However, a reservoir of instability will grow to the southwest due
to heating, extending from eastern NE and KS into IA, with an
effective warm front near the MS river by afternoon. Rejuvenated
convection is expected to form near the warm front/outflow boundary,
possibly aided by outflows, with diurnally driven storms farther
west along the front where heating will be strongest. The greatest
severe threat will extend from the warm front southwestward into
northern KS, with very large hail and damaging wind possible in all
areas. A tornado or two appears most likely from IA into WI, where
low-level shear will be strongest and with the lowest boundary layer
Temperature/Dewpoint spreads. Storms are expected to increase in
coverage into Kansas along the cold front during the evening with a
more linear storm mode expected and damaging wind threat. Portions
of the area may be upgraded in subsequent outlooks.

Farther west, a narrow plume of 50s dewpoints will back into eastern
CO late in the day, where strong heating will lead to steep lapse
rates through a deep layer, with the possibility of a
localized/small MCS developing into western KS where warm
temperatures will exist.

..Jewell.. 06/26/2017

$$