SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1231 PM CDT Sat May 06 2023
Valid 071200Z - 081200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF EASTERN NEBRASKA...IOWA...NORTHERN MISSOURI...EXTREME WESTERN
ILLINOIS...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
NORTHWEST TEXAS INTO FAR SOUTHWESTERN OKLAHOMA...
...SUMMARY...
Severe storms with very large hail, hurricane force gusts, and
isolated tornadoes will be possible across parts of the Mid Missouri
Valley on Sunday. Severe wind/hail producing storms will also be
possible in parts of the central and southern Plains, perhaps
extending into parts of the southern Great Lakes and Ohio Valley
into the Tennessee Valley and central Appalachians.
...Synopsis...
A relatively complex convective scenario is in store for
tomorrow/Sunday. An upper ridge will become established over the
Mid-MS Valley and OH Valley regions while a mid-level trough will
meander over the Interior West. Multiple mid-level impulses are
expected to crest the ridge through tomorrow, potentially supporting
multiple rounds of storms (including possible MCSs), some of which
may be capable of supporting severe hazards. Meanwhile, a surface
low and trailing dryline will become established across the Central
and Southern Plains. Despite relatively weak shear in the presence
of capping, some storms may develop across the southern Plains,
supporting a severe threat.
...Central Plains into the Midwest...
Multiple intense thunderstorms are expected to develop along a warm
frontal zone across eastern NE into IA by late afternoon. Upper 60s
to low 70s F dewpoints beneath 8+ C/km mid-level lapse rates will
support over 4000 J/kg SBCAPE in spots amid elongated, slightly
curved low to mid-level hodographs. Initial development should be
supercellular with very large hail possible and perhaps a couple of
tornadoes possible. However, overall modest shear profiles support
supercell mergers into an intense MCS somewhere from far eastern NE
into the southern half of IA by evening. Should this occur, a
bow-echo MCS may manifest and produce several instances of severe
gusts, a few of which may exceed 65 kts.
...Southern Plains...
Isolated to potentially scattered thunderstorms should rapidly
develop ahead of the dryline by afternoon peak heating. Upper
60s/lower 70s F surface dewpoints beneath 8-9 C/km mid-level lapse
rates will support up to 4000 J/kg MLCAPE wherever low-level
moisture does not mix out. Some guidance suggests that the
development of a well-mixed boundary layer may result in only 2500
J/kg MLCAPE. Nonetheless, very high amounts of buoyancy amid steep
tropospheric lapse rates should support intense thunderstorm
development. With somewhat elongated hodographs, initial updrafts
may be transient supercellular, with the risk of large hail.
However, weak low-level shear should support outflow dominant storms
with a severe wind threat.
...Mid MS Valley, TN/OH Valleys, Central Appalachians...
Multiple MCSs may occur through the day, with an MCS expected to be
traversing the mid-MS Valley into the OH/TN Valley areas at the
start of the period (Sunday morning). This MCS should be in the
weakening stages due to the stabilizing of the boundary layer.
However, the MCS will move southeast along the eastern periphery of
the upper ridge and 7+ C/km mid-level lapse rate plume, where at
least some deep-layer and low-level shear will be present. As such,
a few damaging gusts may still occur, including over portions of the
central Appalachians, where increased diurnal heating may support a
brief re-invigoration of convection along the leading line. It is
possible that the intense MCS moving across the Midwest during the
evening may approach the Mid MS, OH and TN Valleys overnight. Should
this MCS endure, isolated damaging gusts will again be a concern.
...Portions of the northern High Plains...
Scattered thunderstorms may develop along the higher terrain of the
Black Hills by afternoon peak heating in the presence of surface lee
troughing. A warm, but dry boundary layer is expected to materialize
by late afternoon in advance of the storms, with up to 9 C/km
low-level lapse rates expected. Modest strengthening of the vertical
wind profile will contribute to elongated hodographs, fostering the
potential for storm organization. As such, short line segments may
produce isolated severe gusts during the late afternoon hours.
..Squitieri.. 05/06/2023
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