LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0748 AM CDT Sat Apr 08 2023
Valid 081300Z - 091200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
A few strong thunderstorms are possible in the I-10 corridor across
northern Florida through early evening; however, organized severe
weather appears unlikely.
...Synopsis...
Overall, the mid/upper pattern across the CONUS will be fairly low
in amplitude through the period, with the possible exception of the
amplifying southern part of a synoptic ridge crossing the northern
Plains and Upper Midwest, ahead of a trough now over the northern
Rockies and Great Basin. Low-level theta-e ahead of that trough
will be too weak to support a severe threat. However, large-scale
lift preceding the trough, and weak moisture, will support isolated
thunder potential across parts of the central/southern Rockies, with
aid from low-level frontal forcing over parts of NE.
Farther southeast, a southern-stream shortwave trough was apparent
in moisture-channel imagery over parts of AR/LA, and is forecast to
move eastward across the southern Atlantic Coast late tonight. A
quasistationary surface front was analyzed at 11Z off the SC/NC
coastlines, between NOAA buoys 41013 and 41002, southwestward across
northern parts of the JAX area, then westward approximately along
I-10 to a low near PNS. A cold front was drawn from there
southwestward over extreme southeastern LA to the northwestern Gulf.
The low is expected to migrate erratically eastward along the
frontal zone and weaken through this evening. As the shortwave
trough aloft approaches, a second, ultimately stronger low will form
by late this evening over Atlantic waters off the Carolinas, leading
to cold frontal passage over the FL Panhandle and parts of northern
FL by 12Z tomorrow, with the front then extending southwestward
across the central Gulf.
...FL Panhandle to northern FL...
Widely scattered to scattered thunderstorms in clusters should
affect the area through this afternoon and perhaps into early
evening. Strong gusts are possible, and with some help from boundary
interactions, a brief supercell cannot be ruled out. Relative
thunderstorm concentrations most probable over two areas:
1. Immediately ahead of the surface low and near the front across
parts of the Panhandle, where both large-scale lift aloft and
frontal lift each will be maximized, and
2. Near the intersection of the diurnal, north/south-oriented
peninsular sea-breeze boundary with the front, roughly in the
JAX-Lake City corridor.
Weak mid/upper-level lapse rates will substantially limit buoyancy,
despite the rich boundary-layer moisture manifest in upper 60s to
low 70s F surface dewpoints. The modified JAX RAOB (TAE being
unavailable) and forecast soundings suggest peak MLCAPE in the
500-1000 J/kg range, with the greatest buoyancy somewhat less and in
a narrower corridor eastward from Apalachee Bay. Weak low-level
winds (generally 5 kt or less in the lowest km) will limit both
low-level and deep shear, even with strong mid/upper-level venting
flow. Effective-shear magnitudes of about 25-35 kt will be common,
but may spike higher locally around any favorably oriented
baroclinic (front, outflow, sea breeze) boundary processes. In
response to the aforementioned Atlantic frontal-wave cyclogenesis,
flow across northern Fl will veer from around 03-06Z onward,
reducing both vertical shear and lift. Contemporaneous with a
nocturnally stabilizing boundary layer, convective potential should
weaken considerably through late tonight.
..Edwards/Smith.. 04/08/2023
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