431 
ACUS48 KWNS 090835
SWOD48
SPC AC 090833

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0333 AM CDT Sun Aug 09 2020

Valid 121200Z - 171200Z

...DISCUSSION...
...Wednesday/Day 4 and Thursday/Day 5...
The medium-range models move a shortwave trough across the northern
High Plains on Wednesday. A corridor of moderate instability is
forecast across the central and northern Plains Wednesday afternoon.
Some solutions suggest that thunderstorm development may occur along
the western edge of the stronger instability in the western and
central Dakotas late Wednesday afternoon. If this scenario plays
out, then a severe threat would be possible across the Dakotas
during the late afternoon and early evening.

On Thursday, the models are in decent agreement with cyclonic
west-southwest mid-level flow located in the northern Plains. An
axis of moderate instability is forecast in the eastern Dakotas by
afternoon. In spite of this, the models keep the airmass capped
suggesting that convective coverage would remain sparse. If the cap
is weaker than forecast and convection does develop, then an
isolated severe threat can not be ruled out for parts of the
northern Plains Thursday afternoon and evening.

...Friday/Day 6 to Sunday/Day 8...
An upper-level trough is forecast to move across the northern
Rockies on Friday as a mid-level jet moves into the northern High
Plains. Although the ECMWF and GFS differ on the timing of the
upper-level trough, both solutions suggest convection could develop
by evening in parts of eastern North Dakota and northwestern
Minnesota. Forecast instability and shear would be strong enough for
an isolated severe threat under this scenario.

On Saturday and Sunday, the models are in good agreement, moving a
cold front southeastward across the upper Mississippi Valley and
into the Great Lakes region. Isolated severe thunderstorms could
develop along parts of the front each day. But uncertainty is
substantial at this range concerning various factors including the
magnitude of instability and the timing of the front.

..Broyles.. 08/09/2020