SPC AC 031252

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0752 AM CDT Fri May 03 2024

   Valid 031300Z - 041200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NEAR THE
   WEST TEXAS CAPROCK ONTO ADJOINING LOW ROLLING PLAINS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   ENHANCED AREA...AND OVER PORTIONS OF THE CENTRAL PLAINS...

   ...SUMMARY...
   Large hail and damaging gusts are possible over parts of the
   central/southern Great Plains from southern Nebraska to west Texas,
   along with some tornado potential over parts of west Texas.

   ...Synopsis...
   Today's transitional mid/upper-level synoptic pattern is a tale of
   two cyclones -- one astride the Upper Midwest/Canadian border, and
   another digging southeastward out of the Gulf of Alaska.  The broad,
   complex leading cyclone will eject northeastward over MB and
   northwestern ON through the period.  A trailing shortwave trough --
   apparent in moisture-channel imagery over parts of southern ID and
   northern NV -- will move east-northeastward to eastern SD and
   central NE by 12Z tomorrow.  The strong, well-developed Pacific
   cyclone will proceed southeastward to just off the coast of OR by
   the end of the period.  Southwest flow aloft will be maintained with
   weak synoptic-scale height rises over most of the central/southern
   Plains.  Still, sufficient moisture, buoyancy, lift and shear are
   apparent for a couple relative maxima in severe potential as
   discussed below.

   At the surface, 11Z analysis showed a low attached to a cold front
   over south-central WY.  The front should proceed southeastward
   through the day, extending from southeastern SD to western NE an
   central CO by 00Z, with the low over northeastern CO.  By 12Z
   tomorrow, the front should extend from a low over IA to south-
   central KS, the northern TX Panhandle, and north-central NM.  This
   front will overtake a developing dryline over the central High
   Plains from north-south, with the dryline position at 00Z over
   eastern CO, the western TX Panhandle, and Permian Basin.  A weak/
   residual, nearly stationary front extended from a low near FST
   northeastward across northwest TX, eastern OK and the Ozarks, and
   should continue to lose definition amidst considerable convective
   outflow.  The southern rim of that outflow was evident from
   southeast TX (between GLS-BPT) across the HOU metro then west-
   northwestward to near SJT.  The western part will shift northward
   slowly through the day toward the front, which itself should drift
   northward up the Caprock.

   ...West/southwest TX...
   Widely scattered to scattered thunderstorms are expected to form
   this afternoon near the dryline and the residual outflow boundary
   over the South Plains to Low Rolling Plains/Concho Valley regions. 
   Isolated to widely scattered convection possible farther south off
   the dryline past the Rio Grande, and into strongly heated/CINH-
   minimized higher terrain of the Serranias del Burro range in
   northern Coahuila.  This activity should move eastward across areas
   below the Caprock and around the Big Country to Edwards Plateau,
   with potential for some of the Mexican convection to cross the Rio
   Grande this evening as well.  Supercells -- with large to very large
   hail and at least isolated potential for tornadoes -- will be more
   probable in and near the 30%/"enhanced" hail area.  Dryline and
   orographic activity to the south will be an early hail/wind threat. 
   Some of this activity may aggregate into clusters offering mainly
   strong-severe gusts, with one or two small MCSs possible this
   evening into the early overnight hours.

   Despite multiple days of MCS and smaller-scale convective activity
   to the east and southeast, a reservoir of rich low-level moisture
   remains not far upstream across south-central TX and into the
   southern Edwards Plateau, where upper 60s to low 70s F surface
   dewpoints and PW commonly 1-1.5 inches.  When advected northwestward
   amid diurnal heating and beneath steep midlevel lapse rates,
   3000-4000 J/kg MLCAPE should become common.  Though low-level flow
   should not be particularly strong, it will be backed, contributing
   to elongated hodographs ad around 30-40 kt effective-shear
   magnitudes.  Splitting storms may be common early, offering the
   greatest hail potential (size and coverage).  The damaging-wind
   threat will be maximized on the mesoscale where organized cold pools
   can develop, and should extend farther east at greater density than
   the hail potential this evening into tonight.  In the absence of
   substantial large-scale support, tornado potential will be locally
   maximized with any supercells that can interact favorably with
   outflow boundaries or each other.

   ...Central Plains...
   Large hail and severe gusts are possible from mid/late afternoon
   into tonight, from thunderstorms shifting eastward across portions
   of the central Plains.  Though nowhere nearly as moist as the TX
   outlook area, a diurnally destabilized plume of moist advection
   should support a secondary relative max in severe potential
   along/ahead of the cold front and dryline from parts of eastern CO
   to western/northern KS and southern NE.  Convection should develop
   by mid/late afternoon in a regional convergence maximum near and
   northeast of the surface low, with MLCINH weakened by favorable
   diurnal heating.  Surface dewpoints in the 40s to low 50s F should
   be common, with steep surface-500-mb lapse rates, 500-1000 J/kg
   MLCAPE and well-mixed subcloud layers.  Effective-shear magnitudes
   around 40-50 kt indicate potential for organized convection -- both
   in quasi-linear form near the front and initially discrete (but
   later merging upscale) off the dryline.  Though activity will
   encounter a more-stable boundary layer with time and eastward extent
   across KS/NE, at least marginal severe-gust potential may last
   overnight as far eastward as parts of the Missouri Valley region.

   ..Edwards/Broyles.. 05/03/2024

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