SPC AC 081723
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1123 AM CST Wed Feb 08 2023
Valid 091200Z - 101200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE SOUTHEAST AND THE GREAT LAKES/OHIO VALLEY...
...SUMMARY...
Isolated severe thunderstorms are possible on Thursday across the
Southeast including parts of Alabama, north Florida and Georgia, as
well as the Midwest including Indiana, Ohio, and southern Michigan.
...Synopsis...
A mid-level shortwave trough and attendant jet streak will move
across the Great Lakes/Ohio Valley region on Thursday. Meanwhile,
the larger-scale positively tilted trough will amplify across the
central CONUS and into the Southern Plains. A ~1000mb surface low is
expected to be located in the vicinity of central Illinois at 12Z
Thursday. This surface low is expected to maintain its intensity
around 1000 mb as it moves northeast into southern Ontario by
Thursday evening. A cold front will trail this surface low and could
be the focus for severe convective wind gusts across portions of the
Great Lakes/Ohio Valley during the day Thursday. Farther south along
the cold front, limited forcing should keep thunderstorm activity
minimal in eastern Tennessee/Kentucky. However, more robust
convection is expected across portions of the Southeast where
low-level Gulf moisture should provide ample instability for a few
strong to severe storms amid broad, weak ascent.
...Ohio Valley/Great Lakes...
An unseasonably moist low-level airmass will be present ahead of the
cold front Thursday morning with a HREF ensemble mean dewpoint in
the mid 50s across eastern Indiana. This will result in low-level
buoyancy along and ahead of the cold front Thursday morning. In
fact, convection will likely remain quite shallow with forecast
soundings showing an equilibrium below 3km. However, strong forcing
from frontal convergence and dCVA across the region should lead to a
fast moving broken line of convection during the day. Lightning is
unlikely with this activity due to its shallow nature, but
convection along the cold front could bring strong to potentially
severe winds to the surface given the 70-75 knot 1km flow across the
region. Extensive cloud cover and minimal boundary layer heating
should keep mixing depth shallow. However, if even brief clearing
can occur ahead of the front with some boundary layer heating, a
greater threat for severe wind gusts will likely occur. If this were
to occur, it would be most likely across portions of north-central
and northeast Ohio where some CAM guidance suggests some clearing
could occur during peak heating.
...Gulf Coast from far southeast Mississippi to southwest
Georgia/Florida Panhandle...
Remnant Gulf moisture with low to mid 60s dewpoints will remain
ahead of the cold front across southeast Mississippi on Thursday
morning. This best moisture will only extend around ~75 miles inland
and therefore the marginal severe weather threat will be confined to
areas in closer proximity to the coast. The cold front will move
slowly east across this region during the day before stalling by
Thursday afternoon across the central Florida Panhandle. Weak height
falls across the region and convergence along the front should be
sufficient for storm development during the day. A few strong to
severe storms are possible, including the potential for supercell
structures given 35-40 knots of effective shear. However, weak
instability (400-700 J/kg MLCAPE) and weak lapse rates (~ 6 C/km)
will foster a thermodynamic environment which is less than favorable
for a more widespread threat. The primary threats will be damaging
winds from any supercell structures or bowing segments which
develop. In addition, a tornado or two is possible given the
significant directional shear in the lowest 1km, but the relatively
weak flow in this layer (less than 25 knots) and the aforementioned
limited thermodynamic environment should mitigate the overall
tornadic threat.
..Bentley.. 02/08/2023
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