SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0251 PM CDT Thu Mar 17 2022
Valid 172000Z - 181200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH THIS
EVENING OVER PARTS OF OKLAHOMA AND NORTH TEXAS...AND LATE TONIGHT IN
PARTS OF LOUISIANA AND SOUTHERN MISSISSIPPI......
...SUMMARY...
Threats for severe thunderstorms are expected late this afternoon
into this evening over parts of Oklahoma and north Texas, and late
tonight in parts of Louisiana and southern Mississippi. Large hail,
damaging winds and a few tornadoes are possible.
...20z Update - Oklahoma...
The Marginal and Slight risk areas have been expanded a small amount
northward in central and north-central OK. Increasingly agitated CU
is evident in visible satellite imagery over the past hour or so
across western OK, to the northeast of the surface low (centered
near CDS in northwest TX). Convection is expected to develop in the
next 2-3 hours and spread north/northeast across parts of central
and northern OK, posing a threat for large hail, locally strong
gusts and perhaps a tornado. Other than this minor expansion of the
risk area, the forecast philosophy remains unchanged from the prior
outlook.
...LA/MS...
No changes have been made to the outlook for the overnight severe
threat across LA/MS. See previous discussion below for forecast
details.
..Leitman.. 03/17/2022
.PREV DISCUSSION... /ISSUED 1130 AM CDT Thu Mar 17 2022/
...OK/TX this afternoon/evening...
Upper-level trough will move east across the southern Plains through
tonight, with cold mid-level temperatures shifting east in tandem
with modestly increasing low-level moisture. This will result in a
relatively narrow axis of MLCAPE of 1500 to locally 2000 J/kg
developing in advance of a surface low and dryline. Thunderstorm
development is anticipated during the late afternoon/early evening
time frame as MLCIN diminishes and large-scale ascent increases with
the approach of the upper trough. Deep-layer shear will support some
risk for supercell storm structures, and very steep mid-level lapse
rates and substantial CAPE in the hail growth region support a risk
for significant severe hail in addition to damaging gusts. Enlarged
low-level hodographs and lowering LCLs early this evening will
support at least some risk for a tornado before the onset of
nocturnal cooling. Overall, the previous outlook reasoning remains
on track and have made no changes to the severe probabilities in
this area.
...LA/MS overnight...
Thunderstorm development is expected late tonight within an
increasing warm/moist advection regime as the upper trough shifts
east and the marine/warm front lifts north. Strong low-mid level
wind fields will result in effective shear values sufficient for
supercell storms with a risk for all severe hazards. An increase in
tornado probabilities was considered with this outlook over portions
of southwest MS and southeast/east-central LA for the potential for
surface-based storms near the warm front, where a conditional risk
for a significant tornado will exist. However, with concerns
regarding a tendency for veering 850 mb flow during the 08-12z time
frame have opted to maintain current categorical/probabilistic risk
levels and shift tornado probabilities north across portions of
southern MS/east-central LA. Additional adjustments to the risk in
this area may be needed in later outlooks.
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