Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS11 KWNS 221751
SPC MCD 221751
Mesoscale Discussion 0546
NWS Storm Prediction Center Norman OK
1251 PM CDT Sat Apr 22 2017
Areas affected...Central Louisiana northeastward to northwestern
Alabama and Middle Tennessee
Concerning...Severe potential...Watch possible
Valid 221751Z - 221945Z
Probability of Watch Issuance...40 percent
SUMMARY...Damaging wind gusts and hail approaching 1" in diameter
are all possible with storms developing across the region this
afternoon. A WW is being considered.
DISCUSSION...Scattered thunderstorms are continuing to increase
across the discussion area just ahead of a surface boundary
extending from Middle Tennessee, through the Mississippi Delta, and
southwestward into northern Louisiana. The airmass ahead of this
frontal boundary was weakly capped, with insolation/surface warming
and weak low-level warm advection fostering weak to moderate
instability in an axis from central Louisiana northeastward to
Middle Tennessee. Stronger instability was common in southwestern
portions of the discussion area (1500-2000 J/kg MUCAPE), with
gradually weaker instability (500 J/kg MUCAPE) area near Nashville.
Westerly deep shear (around 35 knots) was sufficient for storm
organization, and weak surface convergence combined with ascent
associated with a mid-level low north of the area should foster
gradually increasing convective coverage and intensity with
progression toward peak heating later this afternoon. Hail and
gusty winds will be the primary threats with this activity.
Given the aforementioned scenario, a WW issuance is being considered
for portions of the region.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 31389043 31229118 31219170 31519199 32139195 32759188
33239151 33579116 35228899 36058734 36158653 35978607
35548605 34718631 32958818 31389043