Moderate Risk For All of Tennessee Valley
NWS Storm Prediction Center Norman OK
0952 AM CDT Mon Mar 19 2018
Areas affected...north-central and northern AL...northwest GA...far
southern middle TN
Valid 191452Z - 191615Z
SUMMARY...An upgrade to a Moderate Risk categorical outlook (driven
by a 15% significant tornado risk) is planned for the 1630Z outlook (10:30am CT).
DISCUSSION...It appears increasingly probable the risk for several
tornadic supercells will traverse across northern portions of AL
late this afternoon and through the early evening. Thunderstorm
activity will be largely void across a large part of this area
(north-central AL) prior to peak heating and a moderately unstable
airmass is expected to develop by mid afternoon. The arrival of a
speed max in the mid-levels will correspondingly lead to a marked
strengthening in low-level flow and increasing hodograph size, which
will be more favorable for supercells and low-level mesocyclones.
Given these factors, confidence has increased such that a 15%
significant tornado risk and the potential for longer lived
supercells and damaging tornadoes will focus across north-central
and northern AL, far southern middle TN beginning during the late
afternoon/early evening, then moving east into northeast AL and far
northwest GA later this evening.