ACUS02 KWNS 301709
SWODY2
SPC AC 301707

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1207 PM CDT Thu Jun 30 2022

Valid 011200Z - 021200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHEAST
WYOMING...SOUTHWEST SOUTH DAKOTA AND NORTHWEST NEBRASKA...

...SUMMARY...
Severe thunderstorms producing damaging gusts and hail will be
possible across northeast Wyoming, southwest South Dakota and
northwest Nebraska on Friday. Additional isolated strong
thunderstorms are possible across the central High Plains, the
Mid-Mississippi Valley vicinity, and upper Ohio Valley to central
New York.

...Synopsis...

An upper trough will pivot eastward over the Great Lakes and
Northeast while an upper ridge persists over the central/northern
Rockies vicinity. Stronger mid/upper westerlies will remain confined
to the Great Lakes vicinity around the upper trough. However, a
midlevel shortwave impulse is forecast to eject from WY/CO toward
the central Plains, resulting in some moderate midlevel
northwesterly flow across the northern/central High Plains vicinity.
At the surface, a cold front will progress east/southeast across
portions of the Upper Midwest/Great Lakes. Western portions of this
boundary across KS will stall as it intersects weak lee troughing
near the KS/CO border. The surface cold front and lee trough will
both focus thunderstorm development during the afternoon and
evening, and some severe risk is possible from the High Plains into
the Mid-MS Valley northeast toward the lower Great Lakes.

...Northern/Central Plains Vicinity...

Deep layer flow will remain relatively weak across the region,
however, vertically veering profiles will contribute to effective
shear magnitudes around 30-40 kt (higher across WY/SD).
Southeasterly low-level flow will transport mid 50s to low 60s
surface dewpoints westward along the lee trough from eastern WY/CO
into western SD/NE/KS. While modest boundary-layer moisture will
limit stronger destabilization, MLCAPE values around 1000-2000 J/kg
amid sufficient shear should support organized cells/clusters. Very
steep low-level lapse rates with inverted-v sub-cloud thermodynamic
profiles suggest strong gusts will be the primary hazard. Closer to
the midlevel shortwave impulse and somewhat stronger mid/upper flow
across eastern WY into southwest SD and northwest NE, potential
exists for organized clusters capable of damaging gusts by late
afternoon/evening. Some hail may also accompany stronger cells.

...Eastern KS to IN...

A seasonally moist and strongly unstable airmass will reside ahead
of the southward-sagging surface front. In the absence of stronger
large-scale ascent, modest low-level convergence should be
sufficient for thunderstorm development by afternoon. Vertically
veering wind profiles on the southern fringes of stronger mid/upper
level westerlies will provide adequate shear for widely scattered
loosely-organized convection. Midlevel lapse rates will remain
modest, but strong heating will result in steep low-level lapse
rates, and sporadic strong gusts and possibly some hail will be
possible into early evening. 

...Upper Ohio Valley into south-central NY...

The surface cold front will remain north of the international border
for much of the day. However,southwesterly low-level flow will
transport low/mid 60s F surface dewpoints northward, aiding in a
corridor of moderate destabilization beneath strengthening midlevel
flow (35-45 kt around 700-500 mb). Thunderstorm clusters producing
sporadic strong gusts and marginal hail will be possible into the
evening hours.

..Leitman.. 06/30/2022

$$