Day 4-8 Outlook

Day 4-8 Outlook Image

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0359 AM CDT Thu Oct 08 2020

Valid 111200Z - 161200Z

Medium-range guidance indicates that the westerlies will undergo
considerable further amplification during this period.  It appears
most certain that mid-level ridging will build along a sharpening
axis just west of the U.S. Pacific coast into British Columbia. 
Downstream, ensemble output depicts broad mean troughing east of the
Rockies through the Atlantic Seaboard by late next week, but
solutions are rather dispersive concerning embedded short wave

Greatest certainty exists concerning mid/upper trough amplification
along a negatively tilted axis east of the Rockies through the upper
Mississippi Valley late this weekend into early next week.  This is
forecast to be accompanied by significant surface cyclogenesis
across Saskatchewan into the vicinity of Hudson Bay, with a trailing
cold front surging across and east of the U.S. Great Plains.

The most appreciable severe weather potential with this system still
appears to exist on Sunday, across eastern portions of the northern
Great Plains into the upper Mississippi Valley.  The extent of
northward moisture return in the wake of Delta remains uncertain,
and could remain fairly marginal for vigorous convective
development.  However, a plume of initially steep lapse rates
associated with elevated mixed-layer air may still contribute to a
pre-frontal corridor of sufficient conditional and convective
instability to support severe thunderstorm development.  Aided by
40-50+ kt mean lower/mid tropospheric flow, severe wind gusts may be
the primary hazard across the eastern Dakotas into Minnesota and
parts of the middle Missouri Valley.

With the suppression of the elevated mixed layer, severe weather
potential east-northeastward into the upper Great Lakes region on
Monday still looks more marginal due to less favorable thermodynamic
profiles.  Through the remainder of the period, pattern
predictability remains problematic, but severe weather potential
still appears generally low at this time.

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