LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Tue May 16 2023
Valid 161200Z - 171200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN AND CENTRAL APPALACHIANS...
...SUMMARY...
Strong to severe thunderstorms, associated with wind damage,
isolated large hail and a few tornadoes are expected to develop
across parts of the southern and central Appalachians this afternoon
into early evening.
...Southern and Central Appalachians...
An upper-level trough will dig southeastward today across the Ohio
Valley, as a 45 to 55 knot mid-level jet develops and translates
eastward through the central Appalachians. At the surface, a low
will move eastward across Kentucky today, with moisture advection
occurring ahead of the track of the low. Surface dewpoints are
expected to increase into the lower to mid 60s F across much of the
southern and central Appalachians, where moderate instability will
likely develop by early afternoon. A line segment is expected to
move eastward across southern Kentucky this morning. This line could
be associated with a wind-damage threat. Low-level convergence is
forecast to increase near the surface low. This, along with surface
heating should result in scattered convective initiation around
midday. Several clusters or short line segments are expected to
develop and move eastward across the southern and central
Appalachians this afternoon.
The mid-level jet associated with the approaching upper-level
trough, will steadily increase in strength over the region around
midday. In response, moderate deep-layer shear will develop over
much of the warm sector. Forecast soundings suggest that winds will
be mostly unidirectional from the west-southwest above 850 mb. Also,
0-3 km lapse rates will steepen to near 7.5 C/km. This combination
will be favorable for damaging wind gusts, along the leading edge of
intense multicell line segments. Cells that remain discrete will
have potential to become supercells. Supercells could produce
isolated large hail, and perhaps a few tornadoes. The greatest
tornado threat is forecast to develop during the mid to late
afternoon from southeast Kentucky and northeast Tennessee eastward
into western Virginia and far northwestern North Carolina. The
wind-damage threat is expected to continue into the early evening as
additional cells form in the higher terrain and move eastward into
the foothills of the Appalachians.
...Central High Plains...
An upper-level trough will move southeastward across the central
High Plains today. As surface temperatures warm along a lee trough,
convective initiation is expected in the higher terrain of eastern
Wyoming. Thunderstorms will move south-southeastward along an axis
of instability from western Nebraska into far northwestern Kansas.
RAP forecast soundings at 21Z along the instability axis have MLCAPE
around 1000 J/kg, 0-6 km shear near 36 knots, and 700-500 mb lapse
rates above 8 C/km in a few locations. This should support a threat
for isolated large hail with rotating storms that form during the
late afternoon.
..Broyles/Weinman.. 05/16/2023
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