983
ACUS48 KWNS 210854
SWOD48
SPC AC 210853

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0353 AM CDT Mon Jul 21 2025

Valid 241200Z - 291200Z

...DISCUSSION...
Medium-range models indicate that mid-level ridging, initially
centered over the Ohio Valley, will weaken late this work week
through next weekend, as flow undergoes substantive amplification
upstream.  This appears likely to include a significant short wave
trough digging southeast of the Aleutians, accompanied by
lower/mid-tropospheric cyclogenesis across the northeastern Pacific.
 Part of a higher latitude blocking pattern, little subsequent
movement of this cyclone is forecast through early next week, as an
expansive, prominent mid-level ridge also evolves in the downstream
lower latitudes, across much of the Intermountain West, Rockies and
Great Plains into mid and lower Mississippi Valley.

However, as a notable mid-level low continues slowly east of Hudson
Bay, across northern Quebec and Newfoundland and Labrador, a belt of
seasonably strong westerly mid/upper flow may be maintained across
Ontario and Quebec this Thursday through Friday.  Along the
favorably sheared southern fringe of this regime, seasonably moist
low-level air advecting ahead of a stalled to southward advancing
frontal zone may contribute to sufficient destabilization for the
evolution of organizing thunderstorm clusters capable of producing
swaths of damaging wind gusts.  The extent to which this may impact
U.S. portions of the Great Lakes into New England remains unclear.

It might not be out of the question that a similar type regime could
evolve beneath developing northwesterly mid-level flow, from the
North Dakota/Minnesota international border area into the Upper
Midwest/Great Lakes late next weekend into early next week.  Current
guidance is still suggestive that this is a lower probability, but
this could be due to the low predictability of the pertinent
features at this extended range.

..Kerr.. 07/21/2025