Valid 232000Z – 241200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE HIGH PLAINS REGION…AS WELL AS PARTS OF SOUTHERN VIRGINIA AND
NORTHEAST NORTH CAROLINA…
…SUMMARY…
Severe thunderstorm risk continues this afternoon into early tonight
for portions of North Carolina and Virginia, as well as the central
High Plains.
…Discussion…
Evolution of ongoing convection remains largely in line with the
most recent outlook reasoning and areal outlines. Storms are
increasing across parts of southern Virginia, within the SLGT risk
area, and where newly issued WW #612 is in effect. Farther west,
convection remains thus far subdued over the high Plains, but should
increase over the next couple of hours. For additional short-term
information across this area, please refer to recently issued MCD
#1839.
..Goss.. 08/23/2019
.PREV DISCUSSION… /ISSUED 1125 AM CDT Fri Aug 23 2019/
…VA/NC this afternoon/evening…
A surface cold front will continue to move slowly southward across
VA this afternoon into NC overnight, in the wake of a midlevel
trough crossing New England. The southern fringe of the westerlies
extends south to near the VA/NC border, where a series of subtle
speed maxima/embedded MCVs will translate eastward this afternoon.
Low-level convergence/ascent along the front and an accompanying
differential heating zone should support thunderstorm development by
early afternoon across central VA, and storms will spread
east-southeastward through the remainder of the afternoon/evening.
Though midlevel lapse rates will be rather modest, surface heating
will steepen low-level lapse rates and boost afternoon MLCAPE to
near 1500 J/kg. Given effective bulk shear in the 25-35 kt range,
and mix of organized multicell clusters and some low-end supercells
can be expected in a broken band along the front this afternoon.
Damaging winds should be the main severe threat.
…Central High Plains this afternoon into tonight…
A midlevel shortwave trough is moving slowly eastward over the
northern Rockies, as other subtle embedded waves progress eastward
over the central Rockies. Steep midlevel lapse rates, daytime
heating, and low-level upslope flow will promote an environment
favorable for afternoon thunderstorm development east of the Front
Range from northeast NM northward into eastern WY. Deep-layer
vertical shear will not be particularly strong over most of the High
Plains. The corridors of the somewhat stronger vertical shear will
be immediately east of the midlevel trough in WY, and in the
vicinity of southeast CO where low-level east-southeast flow will
reside beneath the more westerly flow aloft, contributing to
effective bulk shear of 30-35 kt. Thus, expect a mix of multicell
clusters and some low-end supercells capable of producing damaging
winds and large hail. A few clusters will likely persist into
tonight in association with warm advection and a modest low-level
jet.
$$