540
ACUS01 KWNS 180545
SWODY1
SPC AC 180544

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1244 AM CDT Tue Jun 18 2024

Valid 181200Z - 191200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE UPPER
MISSISSIPPI VALLEY TO THE CENTRAL HIGH PLAINS...

...SUMMARY...
Scattered strong to severe storms will be possible this afternoon
over parts of the Upper Mississippi Valley southwestward into the
central High Plains.

...Upper Mississippi Valley to the central High Plains...

A pronounced upper trough is currently evident over the northern
Rockies. This feature is forecast to eject into the northern High
Plains by 19/00z, then across MB/upper Red River region by the end
of the period. While weak mid-level height falls will extend along
this corridor early, much of the CONUS will actually experience
neutral-weak height rises as the eastern US anticyclone dominates
and builds west into the OH Valley. This evolution will result in a
notable surface low tracking from eastern SD, across northern MN
into western ON by mid afternoon. Building surface pressures over
the Plains will force a cold front southeast and this boundary will
serve as the focus for potentially strong/severe convection later in
the day.

Early in the period, strong low-level warm advection will prove
instrumental in a zone of robust convection across the upper Red
River Valley into western ON. As the LLJ lifts northeast in response
to the short wave, the majority of elevated convection will progress
north of the international border. Of more significance will be
convection that develops later in the afternoon along/ahead of the
cold front. Latest model guidance suggests modest boundary-layer
heating will occur ahead of the wind shift and this should aid
buoyancy for potential robust updrafts. Strongest mid-level flow and
deep-layer shear will be noted across the upper MS Valley, but
adequate shear will extend the length of the front into the central
High Plains where a few supercells are expected to develop. The
primary risk for organized updrafts will be during the late
afternoon/evening hours when instability will be maximized. Large
hail and damaging winds are the primary risks.

...Upper Ohio Valley into upstate NY...

Water-vapor imagery depicts at least one significant disturbance
rotating northeast around the anticyclone. This feature is currently
located over IL and should contribute to diurnally-enhanced
convection later today. Current trends/model guidance suggest this
disturbance will advect into lower MI by 18z, then into southern ON
by early evening. Surface heating should contribute to
destabilization across the upper OH Valley into upstate NY and
isolated-scattered thunderstorms will once again develop. Gusty
winds are the primary concern with this weak-modestly sheared
activity.

..Darrow/Thornton.. 06/18/2024

$$