- Moderator
- #1
ACUS48 KWNS 020959
SWOD48
SPC AC 020958
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0358 AM CST Tue Jan 02 2024
Valid 051200Z - 101200Z
...DISCUSSION...
An upper trough over the central CONUS, with multiple embedded
mid-level shortwave troughs over the southern Plains, is forecast to
move eastward across the Southeast and TN/OH Valleys on Day
4/Friday. Similar to prior systems, low-level mass response should
encourage the northward advance of low-level moisture across the
northern Gulf of Mexico and immediate coastal areas of TX/LA/MS/AL.
While both low-level and deep-layer shear appear strong with this
system, current expectations are that appreciable surface-based
instability should struggle to reach very far inland. This will
probably tend to limit the spatial extent of any severe risk over
land Friday afternoon through Friday night from parts of coastal TX
to the central Gulf Coast states. Still, a marginal/isolated severe
risk may exist across these areas, and low severe probabilities may
need to be included in a future outlook. Some severe threat may
persist into Day 5/Saturday across parts of the Southeast as the
upper trough and related surface low/cold front continue quickly
east-northeastward. But, uncertainty regarding sufficient
instability given poor lapse rates and modest low-level moisture
precludes introduction of a severe area at this time.
In the wake of this system, minimal severe potential is evident
across the CONUS for Day 6/Sunday. Medium-range deterministic and
ensemble guidance show remarkably good agreement that another upper
trough will both strengthen and amplify as it ejects across the
southern Plains and Southeast early next week. Impressive wind
fields at low/mid levels should easily support severe thunderstorms
wherever sufficient low-level moisture can advance inland of a
deepening surface low. There is still some uncertainty with both how
quickly rich low-level moisture will be able to return northward
from the Gulf of Mexico into parts of TX and the lower MS Valley,
and how far north it will reach. Regardless, it appears probable
that enough boundary-layer instability will be present/develop on
Day 7/Monday and Monday night over parts of coastal/east TX into LA,
southern MS/AL, and the western FL Panhandle to justify introducing
a 15% severe area. Adjustments to this area will likely be needed in
the coming days as confidence increases in the northward extent of
appreciable low-level moisture. But, given the very strong forecast
shear, supercells and line segments capable of producing both
tornadoes and damaging winds appear possible. This severe threat may
continue farther east into Day 8/Tuesday from parts of FL/GA into
the Carolinas, but too much uncertainty regarding destabilization
currently exists to include a severe delineation across this region.
..Gleason.. 01/02/2024
