SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0653 AM CST Thu Feb 24 2022
Valid 241300Z - 251200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
Thunderstorms are possible today and tonight from the western Gulf
Coast across the lower/mid Mississippi and Ohio Valley regions.
...Synopsis...
Positively tilted, large-scale troughing will persist over the
western CONUS, with a series of lower-end synoptic to small
shortwave troughs traversing the associated cyclonic flow. The
leading perturbation -- evident in moisture-channel imagery from
central WY across western CO, AZ and northern Baja -- should eject
northeastward to the central Plains and southern High Plains by 00Z.
By the end of the period, this feature should reach Lower MI and
the OH/IN border area, in substantially deamplified form. An
upstream shortwave trough -- now over southeastern BC and WA -- will
dig southeastward across the interior Northwest to the northern
Great Basin and southern ID today, before merging with an initially
separate perturbation now over east-central SK tonight. The
resultant trough should be positioned from ND across western WY to
central NV by 12Z tomorrow.
At the surface, 11Z analysis showed a mostly quasistationary frontal
zone from southern NC to a weak, frontal-wave low over eastern TN,
southwestward across central AL and southern portions of MS/LA.
With the oblique approach of the ejecting western trough, a
separate, discrete low should develop along a retreated version of
the frontal wave by 00Z, most likely over western/central KY near
the Ohio River. By that time, the trailing boundary should extend
across western TN, central MS, southwestern LA, and the northwestern
Gulf to south of BRO, again becoming a cold front. By 12Z, the low
should deepen and move to northwestern PA, with cold front across
eastern WV, the Appalachians of VA/NC/GA, eastern/southern AL, to
near the Mississippi River mouth, and slightly farther southeastward
over the northwestern Gulf than 12 hours prior.
...Southeastern LA to northwestern AL this evening/overnight...
Isolated to widely scattered thunderstorms are possible on either
side of the front through the period, with postfrontal convection
dominant before 00Z, and frontal/warm-sector activity more likely
this evening through overnight. The latter may access a favorably
moist warm sector, characterized by surface dew points in the
mid/upper 60s F. Deep-layer lapse rates will be weak:
1. In the low levels, without the benefit of strong diurnal
heating, and
2. In midlevels, with neutral to stable thermal layers (basal EML
remnants that remain evident in upstream 12Z LIX/SHV/JAN/LCH/CRP
RAOBs) lingering in forecast soundings until very near to after
cold-frontal passage.
DCVA-related large-scale ascent with the ejecting mid/upper trough
will remain well behind the surface front. Still, warm advection
may be sufficient to lift/cool the remnant EML base enough to permit
deeper convection near the front. This regime is possible amidst
35-45-kt effective-shear magnitudes, and hodograph somewhat enlarged
on the eastern rim of a departing LLJ whose axis also should be
behind the surface cold front. An isolated, briefly strong
thunderstorm may mature before being undercut by the front, while
embedded within (and training along the axis of) a southwest/
northeast-aligned convective band. However, given a marginal (at
best) kinematic/thermodynamic parameter space expected, and the
anafrontal regime, severe potential remains too conditional/
uncertain to reintroduce a risk area at this time.
..Edwards/Gleason.. 02/24/2022
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