Day 4-8 Outlook

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0342 AM CST Sat Jan 23 2021

Valid 261200Z - 311200Z

...DISCUSSION...
Medium-range models are in reasonable agreement with respect to
evolution of large-scale features through Day 6, after which
divergence in solutions increases through the end of the period.

Even early on in the period, however, differences at smaller scales
-- particularly with an upper short-wave trough ejecting from the
Southwest across the southern tier of the U.S. during the first half
of the period -- complicate assessment of convective potential.

Models generally agree in the maintenance of persistent western U.S.
upper troughing, with the aforementioned short-wave feature progged
to eject eastward, crossing the Four Corners states and eventually
emerging into the central/southern Plains Day 4 (Tuesday).  By Day 5
(Wednesday), as the feature shifts across the Mid and lower
Mississippi Valley and then the Mid South and central Gulf Coast
states, surface cyclogenesis is expected to occur.  With the GFS
stronger/sharper with the upper feature, stronger surface
cyclogenesis is depicted, with a deepening low over the Tennessee
Valley area by Wednesday evening, while the weaker ECMWF solution
places a much weaker low over the southern Alabama/southern Georgia
vicinity.  In either case however, it appears likely that the
boundary layer will remain stable, as a strong baroclinic zone over
the northern Gulf of Mexico just ahead of this system will likely be
slow to retreat northward.  Thus, severe weather is not expected
with this system.

As the system moves offshore Day 6 (Thursday), large-scale ridging
will prevail over much of the country, ahead of re-establishment of
western U.S. troughing.  Therefore, severe weather is not expected
Thursday, and then beyond which pattern predictability diminishes
steadily through the end of the period.

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