SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1106 AM CST Wed Nov 29 2023
Valid 301200Z - 011200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS
SOUTHEAST TEXAS...
...SUMMARY...
Scattered storms, some severe, will be possible during the day on
Thursday, mainly over southeast Texas. A conditional risk for a few
tornadoes will be possible during the day. Otherwise, marginal hail
will be possible extending northward into parts of Oklahoma.
...Discussion...
A rather conditional severe thunderstorm set up is expected on
Thursday, mainly during the morning and afternoon hours across
southeast Texas. A warm advection regime, resulting in widespread
cloudiness and ongoing showers/thunderstorms will be underway at the
beginning of the period as a shortwave trough tracks across the
central/southern Plains vicinity. Upper 60s F dewpoints will be
focused near the Middle and Upper Texas Coast with low to mid-60s F
dewpoints extending northward toward the Red River/ArkLaTex
vicinity. A surface low will develop and shift east/northeast across
OK/MO as a trailing cold front moves southeast across the southern
Plains after 00z.
Forecast vertical shear profiles are impressive with large, curved
low-level hodographs becoming elongated/straight near 3 km. Strong
low-level southerly flow, with around 40-50 kt at 850 mb, is
expected. Effective SRH values greater than 300 m2/s2 near and north
of a warm front across east TX are depicted in forecast guidance as
well. This shear space conditionally would support supercell
thunderstorms.
However, low-level thermodynamics appear problematic. Surface
temperatures and dewpoints may struggle to reach higher than 68-69 F
(except perhaps near the immediate coast). Furthermore, cloudiness
and morning convection will limit heating, and forecast soundings
indicate low-level lapse rates remaining quite poor and nearly moist
adiabatic. HREF members also continue to depict stronger negative UH
tracks than positive UH tracks, which is an indication that storms
may struggle to be rooted near the surface, limiting access to
better low-level vertical shear. Additionally, forecast guidance
shows modest warming through the day in the 850-500 mb layer, while
stronger large-scale ascent remains focused north of the region.
An outlook downgrade was considered. However, if boundary-layer
moisture is greater than forecast, or any stronger heating can
occur, low-level thermodynamics would improve and allow convection
to access better low-level shear, resulting in an increased risk for
a few tornadoes. As such, will maintain the Enhanced (level 3 of 5)
risk with only minor changes/eastward adjustments compared to the
previous outlook based on latest guidance.
Further north across north TX into OK, steeper midlevel lapse rates
are forecast closer to the midlevel speed max. Convection will
remain elevated, but sufficient elevated instability within a
favorable shear environment will support isolated hail in the
stronger cells through early evening.
..Leitman.. 11/29/2023
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