879
ACUS48 KWNS 290859
SWOD48
SPC AC 290858

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0358 AM CDT Wed May 29 2024

Valid 011200Z - 061200Z

...DISCUSSION...
The potential evolution of the mid/upper flow by this weekend into
next week remains rather uncertain, based on the continuing
substantial spread evident in the medium-range model output.  It
currently appears most certain that the westerlies may undergo
substantial amplification across the mid-latitude Pacific into
western North America by the middle of next week, including broad
large-scale mid-level ridging building across the eastern Pacific
through much of the U.S. Intermountain West and Rockies.  This may
be preceded by a period of more zonal flow near the Canadian/U.S.
border area, with a couple of embedded, progressive short wave
troughs.

Models suggest that these waves may be accompanied by surface
cyclogenesis to the lee of the Canadian/northern U.S. Rockies.
Initial cyclogenesis to the lee of the northern U.S. Rockies,
through the middle Missouri and northern Great Plains Red River
Valley, on Sunday may be modest.  However, it appears possible that
increasing flow/vertical shear, and destabilization associated with
low-level moisture return, could become sufficient to support at
least some organized severe thunderstorm potential by Sunday
afternoon into Sunday night.

Guidance is suggestive that surface cyclogenesis with the trailing
wave next Tuesday may be stronger, but it remains unclear whether
this will be focused to the lee of the northern U.S. Rockies or to
the lee of the Canadian Rockies into the Canadian Prairies.

Due to the considerable uncertainties, severe probabilities are
being maintained at less than 15 percent through this period.
However, this could change in later outlook updates for this period,
particularly in the Sunday through Tuesday time frame.

..Kerr.. 05/29/2024