LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 AM CDT Thu Apr 20 2023
Valid 201200Z - 211200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL TX
INTO THE MID MS VALLEY...
...SUMMARY...
Scattered severe thunderstorms capable of hail and severe gusts are
possible from parts of mid Mississippi Valley southwestward into the
Ark-La-Tex and central Texas this afternoon and tonight.
...Synopsis...
A longwave upper trough will deepen over the central CONUS today.
Within the larger-scale trough, one shortwave will move from the
central Plains toward the upper Great Lakes, while another will move
into the southern Plains tonight. A surface low will propagate
east-northeastward toward the upper Midwest, as a cold front sweeps
through the Plains and eventually the Ozarks.
...Southern Plains into the ArkLaTex...
Widely scattered thunderstorm development is expected this afternoon
along a southeastward-moving cold front from parts of Texas toward
the Ozark Plateau. Moderate to locally strong buoyancy will support
intense updrafts, especially along the Texas portion of the front,
though deep-layer shear may be somewhat marginal for much of the
day. Very large hail will be the initial threat, with some potential
for upscale growth this evening and a corresponding risk of
severe/damaging gusts. Low-level flow/shear across TX is expected to
remain rather modest, but may be sufficient for a threat of a
tornado or two with any sustained supercells.
Prefrontal diurnal development will be possible from east-central
into southeast TX within a weakly capped environment, with the
strongest cells in this region capable of hail, locally damaging
gusts, and possibly a tornado. Later tonight, one or more
thunderstorm clusters may move toward the upper TX Gulf Coast, with
a risk of damaging gusts, isolated hail, and possibly a brief
tornado or two.
Uncertainty remains regarding the timing of the cold front across
Texas, and the magnitude of the severe threat late tonight with any
upscale growth toward the Gulf Coast. Depending on shorter-term
observational and guidance trends, higher hail and/or wind
probabilities may eventually be needed.
...Upper Midwest into the Ozarks...
Substantial early-day convection is expected across parts of
IA/MO/WI/IL. Some threat of isolated hail and/or strong/damaging
gusts may accompany the morning storms. In the wake of the early
storms, renewed development is expected along the front from the mid
MS Valley into the Ozark Plateau. Front-parallel flow from AR into
MO will likely result in a messy convective mode, but instability
and deep-layer shear will be sufficient for a hail and wind threat
with the strongest storms.
Farther north into eastern IA and northern IL, there is greater
uncertainty regarding the recovery of instability in the wake of
morning storms, and guidance is generally more muted regarding the
intensity of frontal convection in this area. However, wind profiles
will be favorable for supercells in this region, and a conditional
all-hazard risk will develop if any supercells can be sustained
during the afternoon/early evening.
..Dean/Bentley.. 04/20/2023
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