SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0237 PM CDT Tue Mar 22 2022
Valid 222000Z - 231200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS
LOUISIANA...MISSISSIPPI..AND WESTERN ALABAMA...
...SUMMARY...
A regional severe weather outbreak is expected across the Lower
Mississippi Valley and middle Gulf Coast States today, with some
threat continuing into tonight. Tornadoes, some of which are
expected to be strong, and potentially widespread damaging winds can
be expected.
...20Z Update...
...Portions of the Southeast and Central Gulf Coast...
Line of thunderstorms currently extending from central MS
southwestward into south-central LA continues to progress eastward.
Northern portion of this line over MS has exhibited slightly faster
eastward/northeastward motion than the portion farther south over
south-central LA. The KDGX VAD did not sample a descending
rear-inflow jet, suggesting that any surges within the northern
portion of the line are a result of local downdrafts. This matches
the overall reflectivity evolution noted thus far. This portion of
the line is quickly moving into a less favorable thermodynamic.
Recent mesoanalysis shows MLCAPE generally around 500 J/kg across
east-central MS into west-central AL. This limited buoyancy and lack
of larger scale organization suggests a somewhat limited severe
potential with northeastern extent into more of northern AL. This
matches previous forecast expectations with no changes needed.
Farther south, the environment remains favorable for intense storms,
but the convective mode has limited discrete storms thus far. 18Z
LIX sounding sampled a very impressive wind profile amid
thermodynamics that easily support deep convection. Any storms ahead
of the line that can mature and organize should become supercells
capable of all severe hazards, including tornadoes. Strong wind
gusts and embedded tornadoes may also occur within the line as it
moves through the area, particularly in any sections where
updrafts/downdrafts cause forward surges.
..Mosier.. 03/22/2022
.PREV DISCUSSION... /ISSUED 1137 AM CDT Tue Mar 22 2022/
...Lower Mississippi Valley/Middle Gulf Coast...
A regional outbreak with tornadoes and widespread damaging winds is
still expected to unfold across the region this afternoon.
A composite quasi-linear convective system with embedded bow/LEWP
structures continues an east-northeastward progression into
west-central/southwest Mississippi and south-central Louisiana late
this morning. This QLCS intercepts a northward-developing warm front
that extends southeastward from west-central Mississippi into
southeast Mississippi at this time. East of the QLCS, some increase
in showers/thunderstorms has been noted across southeast Mississippi
near the warm front.
Expectations are that semi-discrete storms, at least on an isolated
basis, are likely to develop ahead of the QLCS, such as the
late-morning showers/few storms across southeast Mississippi,
although the overall meridional pattern and warm sector cloud cover
imply some lingering uncertainty in terms of the extent of free
warm-sector development. Nonetheless, localized cloud breaks and
minimal convective inhibition will support an increasing warm-sector
risk, and with a further strengthening of low/mid-level winds and
elongating hodographs, tornado potential is expected to further
increase through the afternoon, which includes the potential for a
few strong/intense (EF2+) tornadoes as well. A mesovortex or
embedded supercell tornado risk, along with potentially widespread
damaging winds, will otherwise readily exist with the QLCS and any
development immediately preceding it.
The overall severe threat should diminish during the evening through
a combination of the northern portion of the QLCS outpacing
surface-based instability and waning of large-scale ascent near the
central Gulf Coast as the shortwave impulse ejects away from the
region to the north-northeast. Nevertheless, a still strong
low-level jet and presence of rich boundary-layer moisture will
foster a persistent but probably spatially diminishing threat
tonight across parts of Alabama and the western Florida Panhandle.
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