SPC AC 241253

   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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