ACUS48 KWNS 131001
SWOD48
SPC AC 130959
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CST Wed Nov 13 2024
Valid 161200Z - 211200Z
...DISCUSSION...
Some severe potential remains evident across parts of the
southern/central Plains (and potentially farther east) early next
week, though uncertainty remains regarding the most favored corridor
and the magnitude and sufficiency of low-level moisture/instability.
...D5/Sunday - D6/Monday...
On Saturday, a shortwave trough and attendant surface low are
forecast to move across the northern Great Plains. Low-level
southeasterly flow will result in early-stage moisture return into
the southern/central Plains, as a surface ridge shifts eastward
across the eastern CONUS. Meanwhile, a shortwave mid/upper-level
trough initially near the southern CA/Baja coast may evolve into a
closed upper-level low as it digs east-southeastward from late
Saturday into early Sunday. This trough/low is then forecast to
eject northeastward as a negatively tilted trough across parts of
the southern/central Plains from late Sunday into Monday,
accompanied by significant surface cyclogenesis.
The primary uncertainty regarding severe potential for D5/Sunday
into D6/Monday is the magnitude of low-level moisture return and destabilization across the warm sector of the developing surface
low. While low/mid 60s F dewpoints may return into parts of TX and
perhaps OK, with 50s F dewpoints farther north, limited heating and
relatively weak lapse rates will limit buoyancy, with the GFS/ECMWF
and their related ensembles suggesting MLCAPE of 500 J/kg or greater
may be confined to parts of central/south TX, with increasingly
limited buoyancy farther north.
Some severe potential could evolve on D5/Sunday, especially later in
the period when the ejecting shortwave trough may begin to impinge
on richer moisture from southwest into central TX. An intensifying
low-level jet may support development of widespread convection from
late on D5/Sunday into D6/Monday, with a strongly forced band of
convection potentially moving east-northeastward across a larger
portion of the southern/central Plains.
Despite the very limited instability that is currently anticipated
across much of the region, the intense wind fields and strong ascent
associated with the ejecting shortwave trough (as depicted by the
GFS/ECMWF and some ensemble members) could support an organized
severe threat within a low-CAPE/high-shear regime. Uncertainty
remains regarding the most favorable corridor, with the GFS/ECMWF
favoring parts of the southern/central Plains, while some ensemble
members favor a zone farther east from the ArkLaTex into the mid MS
Valley.
...D7/Tuesday - D8/Wednesday...
Some severe potential could continue into D7/Tuesday into parts of
the Midwest and Ohio Valley, though there may be a tendency for
stronger deep-layer flow and ascent to become increasingly displaced
from sufficient moisture and instability.
NHC is currently forecasting a high probability of tropical cyclone
formation late this week into the weekend across the central/western
Caribbean Sea. Predictability remains very low regarding the
possibility for this system to influence severe potential across the
Southeast toward the middle of next week.
..Dean.. 11/13/2024
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