Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Aug 31 2024 08:35:06

ACUS48 KWNS 310834
SWOD48
SPC AC 310833

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0333 AM CDT Sat Aug 31 2024

Valid 031200Z - 081200Z

....DISCUSSION...
Global models are in reasonable agreement with handling of
large-scale features through about Day 5/Wednesday, after which
divergent tendencies become apparent -- particularly with the
handling of a weak short-wave feature moving across the northwestern
U.S. early in the period.  Models depict this feature partially
phasing with a more substantial trough moving across western Canada
within the faster belt of westerlies to the north Day 4/Tuesday, and
then emerging into the north-central U.S. Day 5.  Afterward,
evolution of this trough begins to differ substantially amongst the
models.  The GFS depicts this trough evolving into cut-off low over
the Upper Mississippi Valley/Upper Great Lakes region Day
6/Thursday, which then lingers in place through Day 8 and beyond.
Meanwhile, the ECMWF remains slowly progressive with the trough into
eastern North America through the period.  Given these substantial
differences, convective/severe potential cannot be reasonably
assessed beyond Day 5.

In the Day 4-5 time frame, a cold-frontal advance out of the western
U.S. into the northern Plains -- and eventually the Great Lakes
region -- is expected, in tandem with the progression of the
aforementioned upper trough.  However, with a surface high still
firmly in place from the eastern U.S. westward into the
central/southern Plains, Gulf moisture will remain suppressed, and
thus the likelihood for only meager destabilization across the
pre-frontal warm sector.  Therefore, severe risk is expected to
remain limited, thus not requiring a 15% areal outline associated
with this system through Day 5.

...Goss.. 08/31/2024

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