[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 171901
SWOMCD
SPC MCD 171900
KYZ000-INZ000-TNZ000-ILZ000-MOZ000-ARZ000-172100-

Mesoscale Discussion 1890
NWS Storm Prediction Center Norman OK
0100 PM CST Sat Dec 17 2016

Areas affected...Northeastern AR...western and middle TN...western
and central KY

Concerning...Severe potential...Tornado Watch likely

Valid 171900Z - 172100Z

Probability of Watch Issuance...95 percent

SUMMARY...A tornado watch will likely be needed as buoyancy
continues to increase and sustained deep/convective initiation
occurs over the next few hours.

DISCUSSION...Visible-satellite imagery shows cloud breaks early this
afternoon across the AR/TN portion of the MS valley northeastward
into western KY.  Temperatures have warmed into the lower to middle
70s deg F over the MS valley and are warming into the middle 60s
over the Kentuckiana region.  Along with surface heating, increasing
low-level moisture is contributing to weak destabilization as SBCAPE
and MLCAPE range from 1250 J/kg near Memphis to around 250 J/kg near
Louisville.  Additional destabilization is expected over the next
couple of hours near the Louisville area.  Very strong deep-layer
wind profiles will support storm organization/rotation once
developing updrafts can become strong enough to become sustained.
Area WSR-88D VAD data show 0-1 km SRH in the 200-400 m2/s2 range.
Given weak capping and the continued warm-air-advection regime
aiding in moistening/lifting parcels to their LFC, gradual storm
development and intensification are expected.  The magnitude of
low-level shear will conditionally support an appreciable risk for
low-level mesocyclones capable perhaps of a few tornadoes, in
addition to isolated damaging wind and marginally severe hail with
the stronger storms.

..Smith/Hart.. 12/17/2016

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

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

LAT...LON   35409144 37038946 38648631 38648565 38278531 37568545
            35158878 34979063 35409144
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