563
ACUS48 KWNS 200830
SWOD48
SPC AC 200829

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0329 AM CDT Thu Aug 20 2026

Valid 231200Z - 281200Z

...DISCUSSION...
An upper trough will move slowly across the Northeast Sun/D4 into
Mon/D5, with thunderstorms likely ahead of a cold front. This front
will likely push offshore on Mon/D5 as a surface low ejects
northward across Quebec. A moist air mass will remain ahead of the
front across the Mid Atlantic and into New England, though ongoing
rain and thunderstorms reduce predictability as far as how unstable
it will become on Sun/D4. Also mitigating overall severe risk
appears to be relatively modest low-level wind speeds, with 10-20 kt
at 850 mb. These areas will be monitored for possible low severe
probabilities in the coming days.

To the west, low severe probabilities are possible over parts of the
northern High Plains, as a small but progressive shortwave trough
moves out of the Northwest and across the northern Rockies atop the
upper ridge. West to northwest winds across the northern High Plains
combined with a lee trough and ribbon of 2000 J/kg MUCAPE should
support at least isolated hail/wind activity, perhaps from eastern
MT into the Dakotas.

Additional storm potential, generally low-end, will be possible
Tue/D6 into Wed/D7 over much of the Midwest to Great Lakes, though
predictability is quite low in forecasting the track of the northern
wave, which may begin phasing with a developing upper low over
Ontario.

..Jewell.. 08/20/2026