SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1221 PM CDT Mon May 15 2023
Valid 161200Z - 171200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TUESDAY AFTERNOON
AND EVENING ACROSS PARTS OF CENTRAL AND EASTERN KENTUCKY...EASTERN
TENNESSEE...SOUTHWESTERN INTO SOUTH CENTRAL VIRGINIA...WESTERN AND
CENTRAL NORTH CAROLINA....UPSTATE SOUTH CAROLINA AND ADJACENT
NORTHEASTERN GEORGIA...
...SUMMARY...
Clusters of thunderstorms may form and gradually consolidate across
parts of the Tennessee Valley and Cumberland Plateau through the
Appalachian Piedmont Tuesday afternoon and evening. Some of these
storms may initially be accompanied by a risk for severe hail,
before strong wind gusts become the more prominent potential severe
hazard.
...Synopsis...
A vigorous short wave impulse digging around the western through
southwestern periphery of a mid-level low, now digging into northern
Quebec, may contribute to elongation of the low and/or amplification
of larger-scale, positively tilted mid-level troughing across much
of the Northeast during this period. As this occurs, it appears
likely to be accompanied by a significant surface cold front, which
is forecast to surge south of the St. Lawrence Valley and upper
Great Lakes region, into the northern Mid Atlantic coast, upper Ohio
and Mississippi Valleys by 12Z Wednesday. A stalled, or slower
moving, and weaker preceding front, initially extending across the
Mid Atlantic coast into the lower Ohio Valley and southern Great
Plains, may advance southward into the Tennessee Valley and through
the southern Mid Atlantic coast, in response to the progression of a
weak frontal wave.
Upstream of the broadly confluent mid-level regime evolving east of
the Mississippi Valley, models indicate that mid-level ridging will
build across British Columbia, with an embedded high evolving, in
the wake of a significant short wave perturbation digging into the
Canadian Prairies. It appears that the latter feature will be
accompanied by lower/mid-tropospheric cyclogenesis, and another cold
front which may advance across the international border to the east
of the northern Rockies by 12Z Wednesday.
...Lower Ohio/Tennessee Valleys into Mid Atlantic...
Along and ahead of the initially stalled or slow moving surface
front, a seasonably moist boundary-layer across the lower Ohio and
Tennessee Valleys is forecast to destabilize with daytime heating,
while also advecting across the Appalachians, toward the Mid
Atlantic, during the day. Despite the presence of only modestly
cool mid-level temperatures, with generally weak lapse rates, this
moisture may become supportive of mixed-layer CAPE on the order of
1000-2000 J/kg (with larger CAPE remaining west of the Appalachians)
along the frontal zone.
Beneath a corridor of strengthening westerly flow in the 850-500 mb
layer (on the order of 30-50 kt), it appears that the environment
will become potentially supportive of organized convective
development. Initiation of storms may be aided by a couple of
perturbations progressing through the evolving and amplifying
larger-scale cyclonic mid-level flow, with convection tending to
grow upscale and perhaps gradually consolidate into one
east-southeastward propagating cluster and associated surface cold
pool, accompanied by potentially damaging wind gusts.
..Kerr.. 05/15/2023
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