From Birmingham NWS morning discussion:
From a synoptic perspective, there are several bullish factors
pointing toward a potentially significant severe weather event
across the MS/AL region. In fact, the shape of the 500mb trough on
the global models is classic and suggestive of a tornado outbreak
across the Deep South. Of course there are other ingredients that
need to fall into place for that potential to be realized, but we
are seeing trends in that direction. Moisture quality and
instability has improved when looking at the trend of 850-925 mb
dewpoints, but models are very likely not handling the lowest part
of the boundary layer correctly during the overnight hours.
Temperatures on Friday will reach the 80s across the region, and
there is no good reason why temperatures should fall into the mid
to upper 60s during the evening in the midst of southerly winds
and an increasing low-level jet, as shown by some models.
Correcting for this bias suggests that temperatures will be in the
70-73F range as dewpoints increase into the mid to upper 60s.
This should yield more instability than currently depicted by the
GFS and ECMWF. Additionally, cold advection at 500mb is being
indicated, and the leading edge of this appears to be paired with
the expected corridor of severe storms. This should help maintain
or enhance mid-level lapse rates through the event, while
tempering the effects of latent heat release and not allowing the
atmosphere to turn over.