Mesoscale Discussion 0636
NWS Storm Prediction Center Norman OK
1204 PM CDT Tue May 19 2020
Areas affected...Portions of southern North Carolina...northern
South Carolina
Concerning...Severe potential...Watch unlikely
Valid 191704Z - 192030Z
Probability of Watch Issuance...20 percent
SUMMARY...
A damaging gust or brief tornado cannot be ruled out
through the afternoon hours. The localized and brief nature of the
severe threat precludes a WW issuance at this time.
DISCUSSION...Cloud breaks south of an effective warm front have
allowed for adequate diurnal heating and steepening low-level lapse
rates in a richly moist boundary layer. The heating will both serve
as a source of low-level lift for increasing convective coverage, as
well as increasing buoyancy, with up to MLCAPE likely exceeding 1000
J/kg along the warm front. While poor mid-level lapse rates will
limit instability and associated updraft intensity somewhat, ample
sfc-700 mb veering will promote relatively strong low-level shear
(0-1 km SRH of around 100 m2/s2 and 0-3 km SRH around 150 m2/s2 per
latest RAP forecast soundings) in close proximity to the warm front.
Given the strong low-level shear,
the stronger storms crossing the
warm front may produce a damaging gust or perhaps a brief tornado.
Deep-layer shear will be somewhat meager (35 knots of effective bulk
shear) given weaker flow fields below 500 mb, suggesting that
any
supercellular organization would likely be brief. In addition,
relatively limited buoyancy will temporally limit the effective
ingesting of favorable low-level SRH.
