Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri May 30 2025 09:01:23

ACUS48 KWNS 300901
SWOD48
SPC AC 300859

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0359 AM CDT Fri May 30 2025

Valid 021200Z - 071200Z

....DISCUSSION...
As mentioned in WPC's Extended Forecast Discussion, an amplified
split-flow pattern across the CONUS renders below-average
predictability through the period. Will maintain inherited
severe-weather areas for D4-5, with mesoscale severe potential
evident in D6 and beyond but with poor synoptic predictability.

....D4/Monday...
A positive-tilt mid/upper trough should shift east as an embedded
shortwave impulse over the northern Rockies tracks near the
international border over the northern Great Plains. A
northeast/southwest-oriented cold front should accelerate southward
into the central High Plains while a weak frontal wave temporarily
stalls the front over the Red River Valley of the North. There are
pronounced signals for afternoon to evening convection along the
front. Initially steep mid-level lapse rates will be supportive of
scattered severe potential. But it appears that stronger mid-level
flow may lag to the cool side of the front, which may limit a
greater threat.

....D5/Tuesday...
Complex severe potential is expected across the central states.
Low-amplitude shortwave impulses should be progressing across parts
of the northern Upper Midwest to the central High Plains on Tuesday
morning. Some guidance suggests extensive overnight convection may
be ongoing within a favorably diffluent upper-flow regime,
characterized by a coupled southern-stream left-exit and
northern-stream right-entrance regime. This renders substantial
uncertainty on where more robust boundary-layer destabilization
should occur. Warm mid-level temperatures in the southern stream
should yield modest mid-level lapse rates, which further lowers
confidence. Nevertheless, a broad and rich moist sector and adequate
deep-layer shear, along with widespread convection during the
afternoon/evening, indicate scattered severe storms remain possible.

...Grams.. 05/30/2025

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