686
ACUS01 KWNS 111958
SWODY1
SPC AC 111957

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0257 PM CDT Thu Jul 11 2024

Valid 112000Z - 121200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
SOUTHERN ARIZONA...

...SUMMARY...
Severe thunderstorm wind gusts are possible over parts of southern
Arizona from mid-afternoon through early/mid-evening.

Little change was necessary for the 20Z update.

The primary of severe risk continues to be over parts of southern
AZ, downstream of storms now developing along the Rim. The air mass
is destabilizing with heating with 500-1000 J/kg MUCAPE currently.
Modest northeast winds in the midlevels and the unstable surface air
mass should foster west/southwestward propagation later today, with
strong to locally severe gusts possible.

For more information see mesoscale discussion 1579.

..Jewell.. 07/11/2024

.PREV DISCUSSION... /ISSUED 1145 AM CDT Thu Jul 11 2024/

...Arizona...
Widely scattered to scattered thunderstorms are expected to develop
this afternoon over the Mogollon Rim, and smaller mountain ranges to
the south. That will occur as strong insolation at those higher
elevations preferentially removes MLCINH, in the presence of
generally greater low-level moisture than previous days. Some
strengthening of flow aloft is expected over this region on the
southeast periphery of the upper anticyclone. This will support
convective motion off the Rim (and small mountain ranges to its
south), into strongly heated/deeply mixed boundary layers of the
desert floor. Isolated strong-severe gusts are possible from the
relatively early, more-discrete activity, and swaths of
strong-severe gusts are possible as convection moves southwestward
toward the international border.

...Northern High Plains...
Isolated to widely scattered, high-based thunderstorms are expected
to form near the lee trough, where both relatively maximized
convergence and strong surface heating should contribute to enough
lift for convective initiation. The main concern should be damaging
to severe gusts, given the deeply mixed subcloud layer. Isolated
severe hail also may occur, amidst enough deep-layer shear for some
organized thunderstorms (effective-shear magnitudes of 30-40 kt).
Lack of greater moisture and buoyancy will be a limiting factor for
coverage and intensity of convection, which should diminish rapidly
after sunset.

...Southeast Kansas/Southern Missouri...
A few severe storms could develop today to the east-northeast of a
surface wave near the Oklahoma/Kansas border in vicinity of front
that extends into Missouri, which may be somewhat effectively
augmented by lingering early day convection. Moderate to locally
strong buoyancy will exist within a moist environment, with MLCAPE
likely to reach 2500-3000 J/kg. A considerable vertical veering of
winds will exist through the lower/middle troposphere, with around
30 kt effective shear. Instances of severe hail and/or wind gusts
could occur.

...Southern Maine...
Clouds have lingered much of the morning with rather weak lapse
rates noted in the 12z KGYX/Gray Maine observed sounding, but
clearing is occurring from the west and a narrow zone of modest
destabilization should occur this afternoon, within a very moist
environment (lower/middle 70s F surface dewpoints) ahead of a cold
front. Pending sufficient destabilization, a locally severe storm or
two could occur, potentially with an absence of lightning, in the
presence of long/semi-straight hodographs (highlighted by 45-50 kt
winds 3-6 km AGL).

...Central/south-central portions of Illinois and Indiana...
Ample low-level CAPE (100+ J/kg 0-km AGL) near the
southward-shifting boundary could lead to some potential for funnels
or perhaps even a brief non-supercell tornado this afternoon. Some
of the storms could otherwise pose a risk for gusty winds, but the
overall potential for organized severe storms is currently expected
to remain low.

$$