045
ACUS02 KWNS 141732
SWODY2
SPC AC 141730

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Sun Jul 14 2024

Valid 151200Z - 161200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PARTS OF
THE MIDWEST INTO THE OHIO VALLEY...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE CENTRAL HIGH PLAINS...

...SUMMARY...
Strong to severe thunderstorms are likely from the Upper Midwest
into the Mid Mississippi Valley and Upper Great Lakes region
tomorrow (Monday). A focused corridor of damaging winds is possible.
Isolated severe thunderstorms are also possible across the central
Plains as well as south-central/southeast Arizona.

...Synopsis...
A complex severe weather scenario is possible across portions of the
Midwest tomorrow (Monday). Upper ridging will prevail across the
western CONUS as broad cyclonic flow remains in place, centered over
the Upper MS Valley. Multiple mid-level impulses will pivot around
the cyclonic flow from the Midwest into the Northeast, with a
surface lee trough and associated cold front poised to sweep
southeastward into the Midwest and OH Valley regions. Multiple
areas/rounds of thunderstorm development are expected from the
Midwest to the Northeast, with preceding storms exhibiting potential
influence on the evolution of subsequent convective complexes.
Nonetheless, the latest high-resolution guidance consensus, general
synoptic pattern, and regional climatology, all suggest that at
least one focused round of organized severe thunderstorms should
occur across the Midwest at some point from the late morning to late
afternoon hours, perhaps accompanied by a focused corridor of strong
to severe wind gusts. Meanwhile, surface high pressure will dominate
the Intermountain west, with monsoonal mid-level moisture pivoting
around the upper ridge, fostering multiple areas of high-based
strong to isolated severe thunderstorms from the Desert Southwest to
the central High Plains.

...Midwest into the OH Valley...
Multiple convective scenarios may unfold across portions of the
Midwest tomorrow, including the possibility of a focused corridor or
of severe gusts produced by a bow-echo MCS. By late morning/early
afternoon, a pronounced mid-level impulse will quickly traverse the
region, overspreading a generally west-to-east oriented surface
baroclinic zone. Along this boundary, upper 70s F surface dewpoints
will be in place, that in tandem with surface heating, will boost
MLCAPE to at least 3500-4500 J/kg. Given strong mid-level westerly
flow accompanying the impulse, appreciable low-level shear and
modest deep-layer shear is expected, characterized by enlarged and
curved low-level hodographs, but short hodographs aloft. This
environment climatologically favors the development of a progressive
bow-echo capable of producing a focused corridor of severe gusts
(perhaps exceeding 75 mph in spots). Furthermore, some HREF members
also depict possible bow echo development. However, there are some
uncertainties regarding how the bow echo could form, with some
members showing a bow echo approaching from MN/IA from Day 1
convection, or from new convective development over central IA.
Since multiple rounds of preceding convection may also influence the
position of the baroclinic zone and associated gradient of strong to
extreme buoyancy, there is some uncertainty as to exactly where a
bow echo would materialize and track.

A Category 3/Enhanced risk has been introduced in the general region
where a bow echo may form, and these highlights may need some
adjustments during the Day 1 Outlook to account for baroclinic zone
placement, or impacts from preceding convection. 5 percent tornado
probabilities have also been added where a bow echo would most
likely reach mature stage, where line-end and
leading-line/system-scale mesovortices may foster leading-line QLCS
tornado potential. However, even in the event that a bow echo does
not materialize, a surface cold front will approach the Midwest
tomorrow, contributing to linear convective initiation amid
strong/extreme buoyancy, where severe gusts will still be of
concern.

...Portions of the Northeast...
The first in a series of mid-level impulses traversing the cyclonic
flow aloft will approach the northern Appalachians by late
morning/early afternoon, contributing to increasing thunderstorm
coverage during the day. Surface dewpoints exceeding 70 F in several
areas, along with modest mid-level lapse rates (perhaps approaching
7 C/km in spots), will result in widespread 1500-2500 J/kg MLCAPE.
Stronger flow aloft will likely remain west into the OH Valley
though, so vertical shear should be modest at best (i.e. bulk
effective shear values around 25 kts). Pulse cellular and occasional
multicell complexes are possible, accompanied by mainly a damaging
gust threat. Storms should gradually weaken around or after sunset.

...Portions of the Central High Plains...
Upslope low-level flow by late afternoon/early evening, in tandem
with peak afternoon heating, will encourage at least scattered
thunderstorm development along the lee of the Rocky Mountains. 30-40
kts of westerly 500 mb flow pivoting around the north side an
anticyclone will assist in thunderstorms quickly moving into the
central High Plains. Here, thunderstorms will be preceded by a well
mixed boundary layer extending up to 700 mb. Surface to 500 mb lapse
rates should be in the 8.5-9.5 C/km range, which favors deep-layer
convective mixing and associated potential for severe gusts. A
Category 2/Slight Risk has been added to portions of the central
High Plains where thunderstorm clustering is expected to be greatest
(based on the latest high-resolution guidance consensus), and where
cold-pool mergers are most likely to occur.

...Portions of southern into central Arizona...
Thunderstorms are expected to develop along the Mogollon Rim by
afternoon peak heating in central AZ. Easterly mid-level flow
pivoting around the south side of an anticyclone may assist the
storms in moving off of the higher terrain, amid a well-mixed
boundary layer. Surface temperatures approaching 100 F ahead of the
storms, beneath the monsoonal mid-level moisture, will support
MLCAPE exceeding 1000 J/kg in spots. Modest elongation of the
hodographs may result in effective bulk shear values approaching 30
kts, which may support sustained multicellular clusters by late
afternoon into early evening, accompanied by an isolated severe gust
threat.

..Squitieri.. 07/14/2024

$$