Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS11 KWNS 172340
SPC MCD 172340
Mesoscale Discussion 0296
NWS Storm Prediction Center Norman OK
0640 PM CDT Fri Mar 17 2017
Areas affected...Northern AR...Western TN...Far Northern MS...MO
Concerning...Severe potential...Watch unlikely
Valid 172340Z - 180145Z
Probability of Watch Issuance...5 percent
SUMMARY...A few strong storms are possible this evening with a
primary threat of marginally severe hail. The magnitude of the
threat appears too low for watch issuance.
DISCUSSION...At 2330Z, thunderstorms are increasing in coverage and
intensity across far northeast AR into the MO Bootheel. Storm motion
and the presence of widespread low cloudiness in the initiation zone
is strongly suggestive that this activity remains rooted above the
surface. The glancing influence of a shortwave trough moving across
the Ohio Valley and a weak cold front moving into northern AR will
support a continued increase in convective coverage into this
While deep-layer shear is rather strong for surface-based parcels,
activity is expected to remain largely elevated, given increasing
surface-based CIN with time, resulting in only marginal effective
shear for the elevated updrafts. However, steep midlevel lapse rates
noted on this mornings observed soundings and recent objective
mesoanalyses will support some hail risk with the strongest
semi-discrete storms for at least the next few hours.
The initial elevated activity is expected to move quickly into
portions of TN/KY and weaken with eastward extent, while some
development further west is possible along the advancing cold front,
though this activity will likely be rather weak and anafrontal given
weaker large-scale ascent and stronger capping with westward extent.
Overall, the severe threat appears too low for watch issuance.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 36339316 36399248 36399149 36349016 36468916 36598841
36338799 35958801 35438842 35038920 34849008 34699147
34799259 35449391 36329400 36339316