[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 201617
SWOMCD
SPC MCD 201617
KYZ000-TNZ000-INZ000-201715-

Mesoscale Discussion 1098
NWS Storm Prediction Center Norman OK
1117 AM CDT Fri Jul 20 2018

Areas affected...Western KY...Far Southern IN...Far Northern Middle
TN

Concerning...Severe potential...Watch unlikely

Valid 201617Z - 201715Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated damaging wind gusts and hail possible during the
next few hours. Watch in the near-term seems unlikely but additional
thunderstorms are anticipated later this afternoon which will likely
merit watch issuance.

DISCUSSION...A discrete thunderstorms has developed quickly about 30
mi east of PAH in western KY. With the stronger forcing for ascent
still farther west, forcing for the development of this storm is
hard to determine but remnant outflow from earlier weak convection
amidst the broadly confluent low-level flow may have provided enough
lift within the recently uncapped airmass. Low-level airmass across
the region is very moist (i.e. dewpoints in the mid 70s and 100mb
mean mixing ratios over 18 g/kg) and unstable (i.e. MLCAPE over 3000
J/kg per the latest mesoanalysis) and is therefore supportive of
rapid and strong updraft development. Vertical shear is also strong
(i.e. effective shear over 50 kt) and is expected to remain strong
throughout the day. Both of this factor support storm organization
and persistence. One negative factor the warm low to mid-level
temperatures and the somewhat drier airmass above 850mb. Entrainment
of this air could weaken updrafts, especially in the absence of
greater forcing for ascent and related cooling/moistening of the low
to mid-levels. As such, expectation for this early development is
for it to be generally unorganized and sub-severe, largely as a
result of the relative short updraft duration. Even so, given the
strength of the shear and instability, observational trends will be
monitored closely. Additional thunderstorms development is
anticipated later this afternoon.

..Mosier/Hart.. 07/20/2018

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

ATTN...WFO...LMK...OHX...PAH...MEG...

LAT...LON   37038843 37758779 37828696 37408631 36848646 36488692
            36418789 36568835 37038843
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