05/08/2024
Moderate risk issued for east central US 🚨🚨
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FOR
SOUTH-CENTRAL/SOUTHEAST MISSOURI...SOUTHERN ILLINOIS...NORTHWEST
INTO MIDDLE TENNESSEE...WESTERN KENTUCKY...
...SUMMARY...
Numerous severe thunderstorms appear likely Wednesday from parts of
the mid Mississippi, Ohio, and Tennessee Valleys into the southern
Plains. All severe hazards, including tornadoes, very large to giant
hail, and potentially significant damaging winds are possible. Some
of the tornadoes may be strong.
...Synopsis...
Within a seasonably deep upper-level trough, one embedded mid/upper
low is forecast to move eastward from the north-central Plains into
the upper MS Valley, while another mid/upper-level low is forecast
to develop within the trailing portion of the upper trough across
the Great Basin. To the south of the Great Plains midlevel low, an
embedded shortwave trough and attendant jet maximum will move from
the central Plains toward the mid Mississippi Valley. Farther
northeast, a shortwave trough and attendant surface low will move
from the upper Great Lakes region into the Northeast.
...ArkLaTex into the Mid-MS/OH/TN Valleys...
A complex but potentially significant severe weather episode still
appears possible over a broad region from the ArkLaTex vicinity into
parts of the mid MS/OH/TN Valleys. All severe hazards will be
possible, with some threat for strong tornadoes, very large to giant
hail, and swaths of damaging wind.
A very moist and unstable warm sector will already be in place this
morning across parts of OK/TX, and eastward along/south of a warm
front into the mid Mississippi, lower Ohio, and Tennessee Valleys.
Strong to extreme instability (aided by a plume of midlevel lapse
rates spreading eastward from the Plains) and moderate to strong
deep-layer shear will support a potentially volatile severe
thunderstorm environment through the day into the evening.
Initial storm development is expected near/north of the warm front
from southeast KS into southwest MO, which may already be underway
at 12Z with a threat of hail and localized severe gusts. The early
convection will play a major role in the evolution of downstream
severe potential through the day, with some potential for a MCS to
develop and move east-southeastward. Should this occur, a swath of
damaging wind could spread toward the TN and lower OH Valleys, along
with a threat for line-embedded tornadoes and some hail. If morning
convection does not evolve into an MCS, then there may be a somewhat
greater potential for supercell development during the afternoon,
though an eventual evolution into multiple intense storm clusters is
expected with time, with an attendant threat of large to very large
hail and damaging winds (with at least isolated gusts in excess of
75 mph possible).
Storm coverage southwestward into the ArkLaTex region and central TX
remains more uncertain, but the environment across this region will
be quite volatile, with extreme instability and sufficient
deep-layer shear for supercells. Very large to giant hail and
significant severe gusts could accompany any storms in this area
from late afternoon into the evening.
A Moderate Risk for hail and wind has been introduced in the
vicinity of the expected frontal zone position from southern MO into
northwest/middle TN, where multiple storm clusters with significant
severe potential appear possible. Some expansion of this Moderate
Risk to the south/west may be needed, depending on trends regarding
storm coverage into the ArkLaTex region.
The magnitude of the tornado threat will be dependent on storm mode,
with the coverage and longevity of discrete or clustered supercells
remaining highly uncertain at this time. However, any stronger
supercell moving through the warm sector or within modifying outflow
could pose a strong tornado threat, given the magnitude of
instability and sufficient low-level and deep-layer shear. A
corridor of higher tornado probabilities may be needed if confidence
increases in several persistent supercells across the region.
...Southern Appalachians into the Carolinas...
Convection will likely be ongoing this morning across the southern
Appalachians vicinity. Some intensification of this morning
convection, along with potential redevelopment, will be possible
into the afternoon. Diurnal heating of a warm and moist airmass will
support moderate to locally strong destabilization, with MLCAPE
increasing above 2000 J/kg. Moderate midlevel westerly flow will
support sufficient deep-layer shear for storm organization, and a
couple supercells and/or stronger clusters could evolve during the
afternoon and evening. Large hail and strong/damaging gusts are
expected to be the primary hazards, though a tornado cannot be ruled
out with any sustained supercell.
...Iowa and vicinity...
Modest low-level moisture will return to parts of Iowa and adjacent
areas of the Midwest/Plains during the day, though the quality of
this moisture may be affected by early convective development to the
south. Cool temperatures aloft will support MLCAPE potentially
increasing near/above 1000 J/kg, with sufficient deep-layer shear to
support organized convection. Guidance varies somewhat regarding the
placement and magnitude of the most favorable instability, but a
couple stronger cells/clusters will be possible with a threat of
hail, damaging wind, and possibly a tornado or two.
...Parts of New England and the Northeast...
A few strong storms will be possible this afternoon and evening
across parts of the Northeast and New England, in conjunction with
the eastward moving shortwave trough and attendant cold front. The
strongest ascent will likely remain displaced to the north of the
more favorable moisture and instability, but a few cells/clusters
may develop and pose a threat of isolated hail and strong/damaging
gusts.
..Dean/Wendt.. 05/08/2024
