[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 211937
SWOMCD
SPC MCD 211937
NCZ000-SCZ000-TNZ000-GAZ000-ALZ000-212200-

Mesoscale Discussion 1122
NWS Storm Prediction Center Norman OK
0237 PM CDT Sat Jul 21 2018

Areas affected...northeast Alabama...east Tennessee...northern
Georgia...western North Carolina and western South Carolina

Concerning...Severe potential...Watch possible

Valid 211937Z - 212200Z

Probability of Watch Issuance...40 percent

SUMMARY...Isolated to widely scattered storms are expected to
develop this afternoon over a portion of the southern Appalachian
region. Some of the storms will become capable of producing
downbursts winds and possibly some hail. Though a severe
thunderstorm watch issuance is possible, it remains uncertain
whether storm coverage will become sufficient.

DISCUSSION...This afternoon isolated storms are in the process of
developing along an old modifying outflow boundary from northeast AL
into middle and east TN. Other storms are expected to initiate over
the higher terrain of east TN and the western Carolinas. The surface
layer in vicinity of the outflow boundary continues to destabilize
with diabatic warming boosting MLCAPE to 1500-2000 J/kg based on
latest objective analysis. WV imagery shows a band of deeper ascent
accompanying a vorticity maximum spreading southeast through east
TN, along with a mid-level jet that is contributing to 35-45 kt
effective bulk shear. The greater storm coverage will likely remain
confined to eastern KY into northeast TN where vertical wind shear
and instability are weaker. Storms developing farther south across
much of the mesoscale discussion area will probably remain more
isolated to widely scattered, but some of the storms could acquire
mid-level updraft rotation, and a few instances of downburst wind
and hail will be possible. In addition to expected isolated storm
coverage, another potential limiting factor for a more robust severe
threat is weak mid-level lapse rates. Nevertheless, convective
trends will continue to be monitored next couple hours for a
possible WW issuance over a portion of this region.

..Dial/Hart.. 07/21/2018

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...GSP...MRX...FFC...OHX...BMX...HUN...

LAT...LON   35858216 35178190 34648253 33768365 32598476 33088552
            34508591 35798518 36248346 35858216
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