Day 4-8 Outlook

Day 4-8 Outlook Image

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0244 AM CST Wed Dec 09 2020

Valid 121200Z - 171200Z

A low-amplitude shortwave trough embedded within a broader,
large-scale trough centered over the Plains will eject northeast
from the Midwest to the northeastern U.S. on Day 4/Saturday. At the
surface, a low near the mid-MS Valley Saturday morning will develop
northeast to the lower Great Lakes by Day 5/Sunday morning. A cold
front attendant to the low will spread east/southeast across the
Midwest and south-central U.S., extending from western NY/PA
southwestward along the central and western Gulf coast vicinity.
Showers and thunderstorms are expected across parts of the mid/lower
MS Valley into the Mid-South and central Gulf coast on Saturday.
While modest Gulf moisture will return northward ahead of the front,
the boundary layer will remain shallow and meager instability is
forecast, precluding severe thunderstorm concerns. 

By Day 5/Sunday, medium range guidance begins to vary considerably
in the evolution of the larger-scale upper trough over the Plains,
and the associated surface pattern. The aforementioned cold front
will likely continue to push offshore the Atlantic coast and Florida
through early Day 6/Monday morning, but severe potential will remain
low. Beyond Sunday, predictability is low given model variability,
but in the mean, a progressive pattern with a series of short
wavelength troughs appears to be likely. This should limit severe
potential as any deep, higher-quality Gulf moisture return would be

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