ACUS48 KWNS 200844
SWOD48
SPC AC 200842

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0342 AM CDT Fri Jun 20 2025

Valid 231200Z - 281200Z

...DISCUSSION...
...D4/Monday...
A mid/upper-level shortwave trough initially over the northern
Plains and upper Midwest is forecast to move into Ontario on Monday,
along the northern periphery of an amplified upper ridge over the
eastern CONUS. A cold front will move through parts of the Great
Lakes, Upper Midwest and central Plains. The strongest deep-layer
flow may tend to lag behind the front, but moderate to strong
instability could support strong to potentially severe storms along
the front during the afternoon and evening. 

Farther east, strong instability is generally forecast to develop
across parts of the Mid Atlantic into New England. However, due to
the influence of the upper ridge, there is currently little signal
for diurnal storm development across this region on Monday. 

...D5/Tuesday...
Extended-range guidance is in reasonably good agreement that a cold
front will move southward across the lower Great Lakes into New
England on Tuesday. Favorable low-level moisture and strong
instability could support severe-storm potential along the front
during the afternoon and evening. However, coverage of storms is
currently uncertain, due to the lingering influence of the upper
ridge, and a tendency for stronger large-scale ascent to be
displaced well north of the front. 

The western upper trough is forecast to deamplify on Tuesday, with
most guidance suggesting that mid/upper-level flow will tend to
weaken downstream across the Great Plains and upper Midwest.
However, strong to locally severe storms could again be possible
near the front, which may begin to move northward across the central
Plains as a warm front through the day.

...D6/Wednesday - D8/Friday...
Predictability begins to wane by the middle of next week regarding
the evolution of synoptic features across the CONUS, though the same
general pattern of a weak upper trough in the West and an upper
ridge over the East may continue through at least Wednesday. In the
absence of any apparent strong forcing mechanisms, organized severe
potential (if any) may tend be focused near a convectively
influenced front across parts of the Plains into the Midwest and
Great Lakes.

..Dean.. 06/20/2025