Day 4-8 Outlook

Day 4-8 Outlook Image

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0350 AM CDT Sun Apr 18 2021

Valid 211200Z - 261200Z

...DISCUSSION...
Low/mid-level winds will likely strengthen across the Mid-Atlantic
and Northeast on Day 4/Wednesday as an upper trough moves eastward
across these regions. There is still some uncertainty regarding how
much low-level moisture will be present ahead of a cold front. If
enough boundary-layer instability develops by Wednesday afternoon,
then strong/damaging winds appear possible with any storms that can
develop along or ahead of the quickly moving front. At this point,
confidence in organized severe convection producing a swath of
damaging winds remains too low to introduce 15% severe
probabilities. Still, some severe risk appears possible from roughly
eastern NC to southern NY, and this region may need to be included
in low severe probabilities in a subsequent outlook.

Low-level moisture return should begin to occur on Day 5/Thursday
across parts of the southern Plains as another upper trough develops
eastward across the Southwest and northern Mexico. There are still
substantial differences in medium-range guidance regarding the
evolution of this upper trough as it ejects over the southern Plains
on Day 6/Friday. Depending the on quality and northward extent of
the low-level moisture return, enough instability may be present to
the east of cold front and dryline to support organized severe
storms Friday across part of the southern Plains. If a more
progressive and amplified upper trough develops eastward as
indicated by some deterministic guidance, then a severe risk may
also occur across parts of the Southeast next weekend. Regardless,
far too much uncertainty remains regarding the timing/amplitude of
the upper trough and placement of related surface features to
include any severe probabilities at this extended time frame.

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