SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0300 PM CDT Fri Apr 28 2023
Valid 282000Z - 291200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL TO SOUTH-CENTRAL TEXAS...
...SUMMARY...
Destructive hail (some at least as large as baseballs), thunderstorm
gusts potentially exceeding 75 mph, and a couple tornadoes remain
possible this afternoon and evening from north Texas southwestward
into south-central Texas.
...20Z Update...
The northern extent of the Enhanced Risk (across north TX) has been
trimmed with this update. Intense convection, including a supercell,
has recently developed along/just south of the surface triple point
in central TX. Although a left-splitting supercell or two remains
possible, it appears that the greater concentration of severe
hail/wind will remain generally south of the Metroplex. Very large
hail and a tornado remain a possibility with any supercell that can
remain at least semi-discrete. The damaging wind threat will
increase as convection eventually grows upscale into an MCS later
this afternoon and evening, with some potential for isolated
significant severe gusts.
Otherwise, only minor changes have been made to the Marginal Risk
across NC, based on recent surface observations showing a stalled
wedge front draped east-west across much of the state. This area may
have a somewhat better chance for an organized thunderstorm or two
given a favorable combination of instability and deep-layer shear.
But, confidence in any more than an isolated severe hail/wind threat
remains too low to increase severe probabilities. See Mesoscale
Discussion 649 for more information on the short-term threat for
isolated wind/hail across the central Appalachians and vicinity, and
Mesoscale Discussion 650 for more details regarding the isolated
severe threat across NC.
..Gleason.. 04/28/2023
.PREV DISCUSSION... /ISSUED 1125 AM CDT Fri Apr 28 2023/
...TX this afternoon through tonight...
A midlevel shortwave trough over the southern High Plains will
continue eastward over central TX this afternoon/evening, as an
accompanying cold front likewise surges southeastward. Low-level
moisture return is underway from south into central and north TX,
with boundary-layer dewpoints in the 65-70 F range from Waco
southward as of 16z. Strong surface heating/mixing is expected
along the western fringe of the returning moisture, near a remnant
lee trough/dryline across the Edwards Plateau, prior to being
overtaken by the cold front later this afternoon/evening. The
surface heating, in combination with strengthening forcing for
ascent along the cold front (with the approach of the midlevel
trough) will support thunderstorm development by mid afternoon
across central/north TX.
The increasing low-level moisture and surface heating, beneath
midlevel lapse rates in excess of 8 C/km, will result in large
buoyancy in the warm sector this afternoon (MLCAPE greater than 2500
J/kg). Thermodynamic profiles will favor both strong updrafts and
strong downdrafts, while wind profiles will become favorable for
supercells as hodographs lengthen. There will be a window of
opportunity for a couple of tornadoes from about 20-22z near the
path of the surface wave along the cold front, where the stronger
low-level shear/hodograph curvature will coincide with the north
edge of the richer low-level moisture (a little south to southwest
of the DFW area). The initial convection will likely be supercells
with the aforementioned tornado potential, as well as very large
hail near 3 inches in diameter. Forcing for ascent along the front
will support upscale growth into more linear convection by this
evening into central/south central TX. Isolated very large hail
will be possible with any semi-discrete supercells, along with an
increase in the potential for damaging outflow gusts (a few of which
could reach or exceed 75 mph). The storms will continue
southeastward overnight to the middle and lower TX coasts.
...OH Valley to the Southeast this afternoon...
The trailing influence of a midlevel trough will move over OH/WV
this afternoon, along with weak surface reflections. A few cloud
breaks will allow modest surface heating, and destabilization could
become sufficient for isolated strong storms with some hail/wind
this afternoon. The trailing (southeast) influence of the midlevel
trough, and a slow-moving wedge front, could focus a few strong
storms this afternoon across NC. Farther south, the remnants of an
overnight MCS are moving over central FL. Lingering clouds have
slow surface heating in central FL, and the better chances for
isolated strong storms with wind/hail will be in the zones of
stronger surface heating across southeast FL with the sea breeze,
and closer to the FL/GA border.
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