732
ACUS03 KWNS 151930
SWODY3
SPC AC 151929

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 PM CDT Sun Sep 15 2024

Valid 171200Z - 181200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE HIGH
PLAINS...

...SUMMARY...
Strong to locally severe thunderstorms will be possible Tuesday
across a large swath of the High Plains region, mainly from late
afternoon into the evening. Severe gusts should be the primary
hazard, though some hail may also be possible.

...High Plains...
A mid/upper-level shortwave trough initially over the eastern Great
Basin should take on a negative tilt as it advances towards the
northern High Plains. Deep lee cyclogenesis is expected over
northeast WY/southeast MT, with a warm front extending
east-northeast of the low somewhere from eastern MT into the Dakotas
during the afternoon and evening. This low will advance north
towards the MT/SK border area by 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 low and warm front. Aided by the subtropical moisture
plume over the Southwest, morning convection near the Four Corners
region may move across the higher terrain toward the High Plains,
with additional terrain-driven development possible during the
afternoon.

High-based storms 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 substantial uncertainty
regarding the degree of storm organization into the lower
elevations. But with scattered to widespread convection and
increasingly extensive outflow expected with time, sporadic severe
gusts may occur during the afternoon and evening.

Somewhat more favorable low-level moisture and buoyancy may reside
near/north of the warm front, from eastern MT into the western
Dakotas. While stronger ascent and deep-layer flow may not impinge
upon areas north of the front later in the forecast period, there
will be some potential for organized convection to develop during
the evening as the shortwave trough ejects northeastward. A couple
of supercells and/or stronger clusters will be possible within this
regime, with a threat of hail and isolated severe gusts.

...Four Corners region...
Despite the unfavorable time of day, a few strong storms cannot be
ruled out Tuesday morning across the Four Corners region into
western CO/NM, in close proximity to the ejecting shortwave trough.
Wind profiles will be quite favorable for organized convection,
though it remains uncertain if sufficient buoyancy will be present
to support any severe threat during the early part of the day.

...Eastern NC/VA...
With uncertainty already relatively high regarding evolution of the
currently developing offshore low into D2/Monday, confidence remains
too low to delineate severe probabilities for D3/Tuesday. Slower and
more aggressive ensemble members continue to suggest an adequate
SRH/buoyancy combination for low-topped supercells may linger over
eastern NC early in the period and shift into parts of eastern VA.
However, the bulk of guidance still indicates a general weakening of
the low-level wind field during the day.

..Dean.. 09/15/2024

$$