Day 4-8 Outlook

Day 4-8 Outlook Image

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0544 AM CST Sun Jan 24 2021

Valid 271200Z - 011200Z

Latest runs of the medium-range models show fair model-to-model
agreement with respect to large-scale features into Day 6 (Friday
Jan. 29), though even larger-scale similarities between models fade
further into the second half of the period.  This increasing
large-scale disagreement centers around timing of the ejection of a
short-wave trough across the southwestern U.S. Day 6, and then
into/across the central U.S. Day 7.  Depending upon evolution of
this feature, convective potential could increase over the south
central and later the southeastern U.S. during the second half of
the period.  However, predictability concerns in this time frame
preclude any further assessment of convective potential.

Prior to this, through the first half of the period, a short-wave
trough is forecast to move from the central/southern Plains region
at the beginning of the period (Wednesday Jan. 27), to the East
Coast states by the start of Day 5.  Slight differences in the
strength of this feature between the GFS and ECMWF result in more
notable deviations in depiction of associated surface low intensity,
with the GFS more aggressive in terms of surface cyclone development
over the southern Appalachians area, and thus more bullish with
respect to convective potential.  With the ECMWF showing a much more
muted frontal wave much farther south -- shifting from the Gulf
Coast to the southeast Georgia coast -- confidence remains too low
to render a more thorough assessment.  

As this upper feature moves offshore Day 5, strong cyclogenesis is
progged over the Gulf Stream/western Atlantic, with cold high
pressure building southward in its wake, across the eastern half of
the country -- in tandem with large-scale ridging/anticyclonic flow
across most of the CONUS.

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