892
ACUS02 KWNS 160600
SWODY2
SPC AC 160559

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Mon Sep 16 2024

Valid 171200Z - 181200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN THE CENTRAL
HIGH PLAINS AND EASTERN MT...

...SUMMARY...
Isolated to scattered severe gusts and hail are possible Tuesday
across a large swath of the High Plains region, mainly from late
afternoon into the evening. The greater concentrations of severe
storms may occur over the central High Plains and eastern Montana.

...High Plains...
A mid/upper-level shortwave trough initially over the eastern Great
Basin will take on a negative tilt as it advances towards the
northern High Plains. Deep lee cyclogenesis is expected over far
northeast WY/southeast MT, with a warm front arcing east across
parts of the Dakotas. This low will advance north then northwestward
across eastern MT through 12Z Wednesday.

Large-scale ascent will be pronounced within this synoptic regime,
with favorable upper-level difluence, mid-level height falls, and
low-level convergence. However, weak buoyancy and modest mid-level
lapse rates will characterize much of the environment to the south
of the surface cyclone and warm front. Aided by a subtropical
moisture plume over the Southwest, morning convection near the Four
Corners region should move across the higher terrain and expand in
coverage into the afternoon.

High-based storms over the central and southern High Plains will
progress into a well-mixed boundary layer that may initially be
devoid of appreciable CAPE. This lack of greater buoyancy during the
late afternoon to early evening (outside of areas north of the warm
front) yields some uncertainty regarding the degree of storm
intensity into the lower elevations. But with scattered to
eventually widespread convection expected with time, extensive
outflows are expected to push east. The most likely corridor for
severe gusts appears to be over the central High Plains where the
most pronounced 700-500 mb flow should advance ahead of the
negative-tilt shortwave trough. Farther south, a few supercells may
initially develop from parts of NM into southeast CO. Modest
mid-level lapse rates should temper updraft vigor, but marginally
severe hail along with isolated severe gusts will be possible.

More favorable low-level moisture with steep mid-level lapse rates
will reside near/north of the warm front, supporting moderate
buoyancy from northeast MT into ND. While stronger ascent and
deep-layer flow may not impinge upon areas north of the front until
near sunset, organized storms should develop over the higher terrain
by late afternoon and spread north within a backed mid-level flow
regime. A few supercells along with an organized cluster or two may
impinge on the greater downstream buoyancy plume, maintaining
threats for large hail and severe gusts into Tuesday night.

...Eastern NC and southeast VA...
While confidence is modest with the probable inland evolution of PTC
8, the bulk signal across guidance is for a weakening low-level wind
field by Tuesday morning across the NC/VA coastal plain. The
potential for low-topped supercells capable of brief tornadoes
appears too low beyond 12Z Tuesday to warrant a risk highlight.

..Grams.. 09/16/2024

$$