Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Jul 08 2023 08:58:12

ACUS48 KWNS 080858
SWOD48
SPC AC 080856

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CDT Sat Jul 08 2023

Valid 111200Z - 161200Z

....DISCUSSION...
General large-scale/synoptic agreement exist in most recent runs of
the global models through about the middle of the medium-range
period, though subtle difference evident even early in the period
have fairly large implications with respect to locations of greatest
severe potential.

Early in the period, a northward wobble of the Canadian upper vortex
will allow some northward expansion of flat southwestern U.S.
ridging.  This will likewise result in some northward retreat of the
belt of stronger west-northwesterly flow aloft across the central
CONUS.  However, the degree to which these early-period
synoptic-scale tendencies occur differs subtly, which also then
manifests as differences in the southward advance of a surface
baroclinic zone across the northern and central Plains/Great Lakes.

Where this boundary resides, will be a substantial factor in terms
of the zone of primary severe risk Days 4-6, and therefore the
positional differences depicted in the models casts uncertainty with
respect to highlighting risk areas, even as early as Day 4.

With time, as the front sags southward across the Plains, the zone
of greater severe risk will do likewise.  In addition, as the
northern extent of this boundary crosses eastern Canada and
eventually shifts into the northeastern CONUS, some severe risk will
likely evolve from New England southwestward across the Ohio Valley
and into the Plains.  Again though, differences with respect to
timing/location of the frontal advance preclude highlighting
specific risk areas through the medium-range period.

...Goss.. 07/08/2023

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