Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS03 KWNS 170808
SPC AC 170807
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0207 AM CST Tue Jan 17 2017
Valid 191200Z - 201200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE LOWER MISSISSIPPI VALLEY AND CENTRAL GULF COAST STATES...
A marginal severe threat will be possible across parts of the lower
Mississippi Valley and central Gulf Coast States on Thursday.
...Lower Mississippi Valley/Central Gulf Coast States...
An upper-level trough is forecast to move eastward across the
southern Plains on Thursday and approach the lower Mississippi
Valley by late afternoon. At the surface, a trough and associated
gradient of low-level moisture is forecast to move into the lower
Mississippi Valley. A large area of rain may be ongoing at the start
of the period from southeast Texas eastward across much of
Louisiana. As large-scale ascent increases from the west upon the
approach of the upper-level trough, thunderstorm development will be
possible during the afternoon across parts of Louisiana and
Mississippi. NAM forecast soundings from Baton Rouge, Louisiana
northeastward to Jackson, Mississippi at 21Z on Thursday show SBCAPE
near 750 J/kg, 0-6 km shear of 55 kt and substantial speed shear in
the lowest 3 km AGL suggesting that the stronger updrafts could have
potential for hail and gusty winds. However, lapse rates below 7.0
C/km should keep any severe threat marginal.