Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue Jul 09 2024 09:00:42

ACUS48 KWNS 090900
SWOD48
SPC AC 090859

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CDT Tue Jul 09 2024

Valid 121200Z - 171200Z

....DISCUSSION...
Deterministic and ensemble guidance offers a strong consensus on a
general pattern shift involving deamplification of cyclonic flow
over the Great Lakes, Ohio Valley and northeast on day 4 (12th-13th)
through day 6 (14th-15th), but with a weaker version of the longwave
trough lingering in that region through the remainder of the outlook
period.  Meanwhile, the Great Basin anticyclone is progged to expand
and shift eastward toward the central Rockies day 4 through day 6,
then deamplify over the central Plains.  This process should
reinforce an EML over the western plateaus and expand it eastward
across the central Plains.  As that occurs, west-northwesterly flow
aloft should set up between the northern Plains and Great Lakes,
mostly (but not entirely) north of a mean low-level frontal zone
occupying a corridor from the north-central High Plains to the lower
Missouri/Ohio Valleys.

Strong lapse rates related to the EML, atop an enlarging area of
upper 60s to mid 70s F surface dewpoints (from both advection and
evapotranspiration), will yield a high-CAPE parameter space near the
front.  Provided it is not too far removed from that large buoyancy,
the northeastern rim of the stronger EML capping, aligned parallel
to the frontal instability gradient, may provide a favorable
corridor for development/propagation of organized,
severe-wind-producing MCS activity on at least one or two of those
days, from the weekend into early next week.  Activity may be
supported by subtle shortwave troughs embedded in the largely
front-parallel flow.  Confidence in shortwave details, and in which
day the cap is more likely to weaken enough to support suitable
initiation and upscale growth, currently is too low to assign
probabilities to a particular day in the series of somewhat similar
ones, pattern-wise.

...Edwards.. 07/09/2024

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