- Moderator
- #1
Forecast Discussion
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 260845
SPC AC 260845
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0245 AM CST Mon Nov 26 2018
Valid 291200Z - 041200Z
...DISCUSSION...
Models depict a shortwave trough digging across the southwestern
states on Thur/D4, though solutions vary as far as how amplified it
will be, with the GFS less so than the ECMWF. Low-level moisture
will begin returning north across eastern TX into the lower MS
Valley by this time, but in either scenario instability will be too
weak for any severe weather threat.
On Fri/D5, this wave will move into the southern Plains, with
aforementioned model tendencies holding. It does appear that the GFS
is becoming a bit more amplified with time, which is closer to the
ECMWF guidance. In either case, low pressure is likely to form over
the southern High Plains during the day, with dewpoints into the mid
60s F across most of eastern TX and LA, and perhaps as far north as
central AR Friday night if the more amplified ECMWF solution
verifies. Rapid height falls and a low-level jet increasing to 50 kt
will favor severe thunderstorms mainly Friday evening and overnight
from eastern TX into LA and AR. Strong shear profiles will favor
supercells and/or QLCS structures, depending on upper trough
geometry. The less amplified GFS solution would result in a more
focused area of potential, and perhaps more favorable for
supercells, while the more meridional ECMWF solution would support
more of a linear storm mode. Regardless, the threat level is great
enough to depict a 15% area for Fri/D5 for damaging winds and
tornadoes.
Some manner of severe threat will likely persist into Sat/D6 across
MS, AL, GA and TN, but predictability is too low to depict the
greatest threat area given the likelihood of widespread
precipitation and model differences in how the upper trough will
eject.
..Jewell.. 11/26/2018