SPC Dec 9, 2023 1630 UTC Day 1 Convective Outlook

[NorthGeorgiaWX]

SPC 1630Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1036 AM CST Sat Dec 09 2023

Valid 091630Z - 101200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE LOWER
MISSISSIPPI VALLEY...GULF COAST...TENNESSEE VALLEY...

...SUMMARY...
A few tornadoes, damaging thunderstorm wind gusts, and isolated
severe hail are possible today and tonight from portions of the Ohio
Valley southward to the Lower Mississippi Valley and middle Gulf
Coast.

...Gulf Coast/Lower Mississippi Valley/Tennessee Valley...
Region is being increasingly influenced by height falls but
otherwise resides between larger scale influences of an upper trough
over the Upper Midwest and a positive-tilt trough over the southern
High Plains. Increasing warm-sector moisture (generally lower to
some middle 60s F surface dewpoints) ahead of a southeastward-moving
cold front, along with considerable deep-layer/low-level shear, will
be favorable factors for a long-duration severe risk through the
afternoon into tonight. However, the likelihood of a complex/mixed
quasi-linear convective mode casts uncertainty regarding the
magnitude of the severe risk, particularly regarding a
supercell-related sustained/focused tornado risk. It is also noted
that some guidance suggests that 1-3km AGL winds may somewhat weaken
by late afternoon/early evening within the warm sector, while noting
SRH will still remain favorable for rotating/severe storms.

Storms should continue to increase in coverage through early
afternoon, initially near the front across Arkansas northeastward
into western portions of Tennessee/Kentucky. Sufficiently steep
mid-level lapse rates will support some hail potential, especially
the first part of the day, but the tendency for storm clustering
will otherwise limit this overall potential, as well as limiting
prospects for more consequential hail magnitudes. As the boundary
layer warms this afternoon, the potential for initially
semi-discrete supercells will increase along with related damaging
wind risk as well as tornado potential, which will persist through
the afternoon/evening even with a quasi-linear convective mode. 

As warm-sector inhibition further weakens later this afternoon,
additional deepening convection may develop within weak pre-frontal
convergence/confluence regime, mainly across Mississippi into
Alabama, with this development eventually merging with or taking
over as the main convective band this evening. Similarly,
pre-frontal confluence may support isolated supercellular
development along the Gulf Coast/Florida Panhandle vicinity through
late night hours/early Sunday, within a somewhat separate regime
capable of a few severe storms.

..Guyer/Weinman.. 12/09/2023

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