Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Wed Mar 11 2020
Valid 121200Z - 131200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE OZARKS
TO THE LOWER OHIO VALLEY/MID-SOUTH VICINITY...
...SUMMARY...
Severe thunderstorms are possible across parts of the lower Ohio
Valley and Mid South into parts of the southeastern Plains Thursday
afternoon and evening.
...ArkLaTex Vicinity to the Ohio/Tennessee Valley Region...
A shortwave impulse embedded in larger-scale upper trough over the
central U.S. will deepen and eject eastward from the central Plains
to the Great Lakes on Thursday. The main surface low associated with
this system will track eastward across Ontario with a surface cold
front extending south/southwest from the Upper Midwest to western
portions of the southern Plains during the morning. A warm front
will extend eastward from a weak surface low over northern OK into
northern AR/western TN early Thursday, lifting northward toward the
Ohio River during the day. Strong warm advection ahead of the
east/southeastward progressing cold front will allow low-to-mid 60s
F dewpoints to overspread the south-central U.S. from eastern OK/TX
into parts of KY/TN.
Surface heating likely will be limited by cloud cover and areas of
ongoing showers, and strong warm advection between 850-700 mb will
result in pockets of stronger capping. However, a 40-50 kt
southwesterly low level jet will develop by late afternoon/early
evening and pockets of MLCAPE up to 1000 J/kg are forecast
along/just ahead of the cold front/triple point near the MO/AR
border southwestward into southeast OK, as well as eastward near the
warm front across KY/TN. Semi-discrete cells in the warm sector are
possible initially, but clusters are expected to grow upscale into
during the evening as vertical shear become aligned with the frontal
boundary. All severe hazards appear possible, with hail more likely
earlier in storm evolution where midlevel lapse rates are expected
to range from 7-7.5 C/km across western portions of the Slight risk
area. SRH values greater than 250 m2/s2, and enlarged low level
hodographs will support tornado potential in both discrete cells and
within any bowing line segments. Furthermore, intense low level wind
field will support damaging winds through the evening hours as
convection spreads eastward into the OH/TN Valley vicinity.
...Central/Southern Appalachians Vicinity...
Several forecast models indicate isolated storms may develop across
parts of northern GA into Upstate SC/western NC. Dewpoints in the
lower 60s will increase across the region, and backed southeasterly
surface winds are forecast as a surface trough develops near higher
terrain. There is indication that subtle impulses will eject across
the region ahead of the main upper trough, leading to weak upper
forcing and low level convergence along the surface trough. Stronger
heating is likely this far east, and MLCAPE could climb to near 1000
J/kg with marginal low-to-mid level lapse rates forecast withing an
adequately sheared environment. While conditional, any cells that
develop could pose a risk for marginal hail/gusty winds.
...Lower Colorado Valley Vicinity...
An upper low off the coast of southern CA will pivot eastward toward
the Lower CO Valley on Thursday. Surface dewpoints near 60F will
spread northward along the CA/AZ border beneath steep midlevel lapse
rates. Low level shear will be weak, but effective shear will
support some organized cells with strong flow expected in mid and
upper levels. Instability will be limited, but a couple of strong
cells are possible. If trends continue, probability may become
warranted in later outlooks, mainly for a marginal hail risk.
..Leitman.. 03/11/2020
