SPC AC 030559
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Tue Oct 03 2023
Valid 031200Z - 041200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN AND CENTRAL PLAINS...
Thunderstorms, associated with large hail, wind damage, and a few
tornadoes, will be possible this afternoon and evening across parts
of the Great Plains.
...Southern and Central Plains...
An upper-level trough will move into the High Plains today, as an
associated mid-level jet on the eastern side of the system moves
through the central Plains. At the surface, a low will deepen and
move across the northern Plains, as a cold front advances eastward
into the central and northern High Plains. Strong low-level moisture
advection in the central Plains will replenish low-level moisture
ahead of the front. Surface dewpoints will likely reach the lower to
mid 60s F by afternoon from northwest Texas northward into central
Kansas and southern Nebraska. As surface temperatures warm during
the day, moderate instability will develop along and near the moist
axis. MLCAPE is forecast to peak in the 2000 to 3000 J/kg range. As
low-level convergence increases ahead of the front, scattered
thunderstorms will form from west Texas north-northeastward into
west-central Kansas and central Nebraska. These storms will move
northeastward into the stronger instability during the late
afternoon and evening. MCS development will be possible.
RAP forecast soundings at 00Z/Wednesday along the moist axis from
northwest Texas to south-central Nebraska have 0-6 km shear
generally in the 45 to 55 knot range, with 700-500 mb lapse rates
near 7.5 C/km. This will support supercell development with large
hail and wind damage likely in and around the stronger cores.
Hailstones of greater than 2 inches will be possible in association
with the more intense supercell updrafts along this corridor during
the late afternoon. In addition, 0-3 km storm-relative helicity is
forecast to increase into the 200 to 300 m2/s2 range by early
evening, suggesting that tornadoes will be possible with the more
intense supercells as well. Wind damage will also be likely with
supercells and with short bowing line segments. The severe threat is
expected to continue into the mid to late evening, as the low-level
jet gradually strengthens across the region.
Further south-southwest into parts of west Texas, isolated to
scattered thunderstorm development will be likely late this
afternoon into the evening. The environment will favor supercell
development, with a potential for large hail and wind damage.
An upper-level trough will move into the northern Plains today, as
an associated belt of strong mid-level flow on the eastern side of
the system translates eastward. At the surface, a low will deepen
and move north-northeastward across North Dakota during the day, as
a cold front advances eastward in the northern High Plains. Surface
dewpoints will initially be in the 50s F over much of the northern
Plains, but a dry slot will cause drier air to advect into the
region from the southwest. Due to this, a corridor of maximized
low-level moisture will setup further east across eastern South
Dakota and west-central Minnesota. Moderate instability may develop
along the western edge of the moist corridor, where isolated to
scattered thunderstorms will be possible during the late afternoon
and early evening. In addition to the moderate instability, 0-6 km
shear is forecast to be in the 50 to 60 knot range near the
instability axis suggesting the environment will support supercells.
There is some question concerning which mode will be favored. If
supercell mode is favored, then large hail and wind damage can be
expected with the cells. If linear mode becomes favored, then the
wind-damage threat could be the greater of the two threats. The most
likely corridor for severe storms will be across eastern South
Dakota and far southwest Minnesota, where severe weather parameters
are forecast to become maximized.
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