Day 4-8 Outlook

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0300 AM CST Wed Dec 16 2020

Valid 191200Z - 241200Z

...DISCUSSION...
Based on the latest model output, low pattern predictability appears
an increasing concern through this period.  Short wave developments,
within branching flow downstream of a strong mid/upper jet across
the southern mid-latitude/subtropical Pacific, are becoming more
unclear.  In general, though, guidance continues to suggest that
there will be increasing amplification within the flow, probably
including a prominent building mid-level ridge near the Pacific
coast by early next week.  It appears that this may be followed by
downstream large-scale upper trough amplification across the central
and eastern U.S., perhaps accompanied by strong surface cyclogenesis
east of the middle Missouri Valley through the Great Lakes region by
the middle of next week.  

If this occurs, large-scale forcing for ascent and strengthening
deep-layer wind fields and shear within the evolving warm sector
probably will become at least conditionally supportive of increasing
severe weather potential, somewhere east of the Mississippi Valley
into the Appalachians.  It does still seem unlikely that there will
be opportunity for deep boundary-layer moistening over the Gulf of
Mexico, and substantive inland return flow to the warm sector, by
this time.  While this may tend to minimize severe weather potential
with vigorous, deep convective development, it is possible that the
environment could still become conducive to damaging surface gust
potential enhanced by an evolving pre-cold frontal low-topped
convective line.

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