SPC 1730Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1130 AM CST Tue Dec 22 2020

Valid 231200Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE LOWER
MISSISSIPPI VALLEY AND GULF COAST STATES...

...SUMMARY...
Isolated severe thunderstorms are possible Wednesday afternoon/night
from the middle/upper Texas Coast across much of Louisiana,
Mississippi, Alabama, and the Florida Panhandle.

...Synopsis...
A deep upper trough is expected to extend from the Canadian Prairie
Provinces southwestward into the Four Corners early Wednesday
morning. Several shortwave troughs will rotate through this parent
upper trough, contributing to both eastward progression and
continued deepening. Upper flow around the trough will also
strengthen significantly throughout the period, with a corridor of
100+ kt 500-mb winds expected from the Lower Mississippi Valley into
southern Ontario by early Thursday morning.

At the surface, low associated with the lead shortwave embedded
within the larger upper trough will begin the period centered over
east-central Minnesota/northwest Wisconsin. A strong cold front will
extend from this low southwestward through the Middle Missouri
Valley and Oklahoma into southwest Texas. Fast
eastward/southeastward progression of this front is expected
throughout the day, and the front will likely extend from eastern
Lower Michigan south-southwestward into the western Florida
Panhandle by 12Z Thursday.

...Lower Mississippi Valley/Gulf Coast States...
Low-level moisture will increase ahead of the southeastward-moving
cold front, with low/some middle 60s F surface dewpoints becoming
increasingly common by late afternoon/evening from the Texas coast
into Louisiana/southern Mississippi. Semi-prevalent cloud cover will
tend to limit heating with lapse rates remaining poor, resulting in
only modest buoyancy. Regardless, surface-based storms are likely to
develop near/just ahead of the front by late afternoon/early evening
across the middle/upper Texas coastal plain into Louisiana. 

Low to mid-level wind fields will be strong, supporting stronger
storms with any more persistent and deep updrafts. Although there
are some uncertainties regarding the overall magnitude of the severe
risk, damaging thunderstorm gusts will be possible and some tornado
risk may exist as well.

..Guyer.. 12/22/2020

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