SPC AC 250558

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1258 AM CDT Sat May 25 2024

   Valid 251200Z - 261200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS IN PARTS OF
   KANSAS/OKLAHOMA AND FAR SOUTHWEST MISSOURI...

   ...SUMMARY...
   An outbreak of severe thunderstorms is forecast from late afternoon
   into tonight across parts of the central and southern Great Plains.
   A few long-lived supercells capable of intense tornadoes may occur.
   Giant hail and destructive wind gusts are also expected.

   ...Central and southern Great Plains...
   Much uncertainty plagues this outlook cycle, with the level
   4-Moderate risk left as-is. This evening's guidance has trended
   slower and more confined with the boundary-layer moisture return,
   with most CAMs also suggesting earlier afternoon initiation
   occurring along the periphery of the richer moisture in west TX.
   Level 5-High risk potential remains evident with the 00Z HRRR
   indicating a possible tornado outbreak scenario with long-lived
   strong to violent tornadoes. 

   Consensus of evening guidance suggests low-level moisture return
   will be within a confined swath emanating north from the
   south-central TX portion of the Rio Grande Valley into west TX. This
   will occur downstream of a modestly amplified mid-level trough,
   consisting of multiple embedded shortwave impulses, ejecting across
   the West into the central and southern High Plains. Surface
   temperatures west of the dryline will become hot, and most CAMs
   indicate early to mid-afternoon thunderstorm development in the TX
   Big Country/western north TX vicinity. It is probable that this will
   become the southern extent of the overall severe threat with
   slow-moving supercells persisting into the evening. 

   Across OK/KS, richer and deeper boundary-layer moisture ahead of the
   dryline should be confined to western OK through late afternoon. A
   more well-mixed boundary layer is expected farther north in
   western/central KS, while the rich moisture should be shallow in
   central OK before deepening later. Most guidance suggests high-based
   thunderstorms will develop in the late afternoon across southwest NE
   and northwest KS, where mid-level cooling will be greatest. 

   Very large hail and isolated severe wind gusts will be the primary
   threats during the afternoon with relatively elongated/straight
   hodographs supporting potential for left and right-splitting
   supercells. A strengthening low-level jet will aid in the tornado
   threat substantially increasing by early evening. The most volatile
   environment for long-lived, intense tornadic supercells should exist
   over the western half of OK. Primary uncertainty precluding an
   upgrade is the degree of impact earlier afternoon storms to the
   south may have on this setup with left-splits/outflows.

   The northern periphery of the richer/deeper moisture surge and
   robust low-level jet is eventually expected to reach at least into
   southern KS during the evening. Supercells in this region will
   strengthen as this occurs, and become capable of producing
   long-lived, intense tornadoes after dusk. But with time tonight,
   increasing large-scale ascent should support a supercell to bow echo
   to MCS evolution towards the Ozark Plateau vicinity. This should
   yield a swath of damaging winds, with embedded significant severe
   gusts and tornadoes possible as it tracks eastward along the MLCAPE
   gradient overnight. 

   ...Eastern States...
   Three areas of level 1-MRGL risk are forecast today with sporadic
   severe hail and locally damaging winds possible. 

   Remnant morning convection and attendant MCVs may aid in isolated
   severe across parts of the Deep South early, before
   spreading/developing east towards parts of the coastal Atlantic
   Southeast during the afternoon. Separately, a marginal supercell
   wind profile will also exist along the southeast FL sea breeze. 

   Across the Lower Great Lakes to central/northern Appalachians,
   initial mid-level ridging will evolve to a flatter, zonal flow
   regime. The trailing surface front attendant to a nearly stationary,
   occluded cyclone along the southeast MB/northwest ON border area
   should aid in isolated to scattered thunderstorms this afternoon,
   some of which should become strong.

   ..Grams/Moore.. 05/25/2024

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