SPC AC 211946

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0246 PM CDT Thu Apr 21 2022

   Valid 212000Z - 221200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHWEST
   OKLAHOMA AND SOUTH-CENTRAL KANSAS AND NORTHERN KANSAS INTO FAR
   SOUTHEAST NEBRASKA...

   ...SUMMARY...
   Large, damaging hail, severe gusts, and perhaps a tornado are
   possible with any thunderstorms that can develop over parts of
   northwestern Oklahoma to south-central Kansas. Large hail is also
   possible across parts of north-central Kansas into far southeast
   Nebraska this evening into tonight.

   ...20Z Update...
   Surface analysis reveals a sharp warm front extending from southeast
   KS across southwest MO. Thunderstorms have initiated to the north of
   this boundary and these isolated thunderstorms may pose a threat for
   mainly hail over the next couple of hours. Hail probabilities were
   extending southeastward to cover this threat.

   Otherwise, the forecast remains on track with afternoon/evening
   initiation possible near the triple point over the central OK/KS
   border vicinity. 

   Additional elevated thunderstorm development is still expected
   tonight across northern KS and southeast NE, with some hail
   possible.

   ..Mosier.. 04/21/2022

   .PREV DISCUSSION... /ISSUED 1129 AM CDT Thu Apr 21 2022/

   ...Synopsis...
   Latest water-vapor imagery continues to show an upper-level trough
   beginning to deepen across the eastern Pacific off the West Coast.
   Broad height rises are noted across the central CONUS, leading to a
   general amplification of the synoptic upper-level regime. At the
   surface, a weakening low is analyzed over the TX Panhandle with a
   warm front draped to the east/northeast across northern OK into
   northwest AR. This warm front is expected to lift to the north into
   the central Plains by 12 UTC Friday in response to a deepening low
   over the northern Rockies. A dryline currently draped southward from
   the TX Panhandle low will largely remain in place this afternoon
   before retreating west overnight as moisture advection continues.
   Thunderstorm chances this afternoon and overnight will primarily be
   focused along the dryline and warm front. 

   ...Northwest OK/southern KS...
   Despite clearing across western OK, the inversion noted in the 12
   UTC OUN sounding remains apparent in visible imagery across the
   region. This inhibition is expected to linger through the late
   afternoon as the warm front lifts north. The dryline across western
   OK and the eastern TX Panhandle will likely extend northward into
   the afternoon in tandem with the weakening surface low. Convective
   initiation is possible late this afternoon in the vicinity of the
   surface low and the dryline/warm front intersection where lift will
   be locally maximized. The probability of initiation remains somewhat
   low given the lack of stronger synoptic ascent (which is supported
   by recent CAM solutions), but if convection can occur it will mature
   in a favorable supercell environment. Storms will initially support
   a large hail/damaging wind threat with an increasing tornado threat
   after 00 UTC as the nocturnal low-level jet strengthens. Open
   warm-sector convection and/or surface-based convection along the
   warm front appears possible given weak capping by late afternoon and
   would develop in a similar supercell environment, but this threat is
   highly conditional and probability appears low. 

   ...Northern KS/southeast NE...
   Isentropic ascent over the warm frontal boundary is expected to
   intensify through the day and into the overnight hours in response
   to the deepening low across the northern Rockies/northern High
   Plains. Elevated thunderstorms developing within the warm frontal
   zone this evening/tonight will become increasingly displaced to the
   cool side of the boundary overnight given storm motions to the
   northeast. However, strong shear within the MUCAPE layer will
   maintain the potential for organized cells with an attendant hail
   threat. This threat appears most likely across northern KS into
   southern NE where the potential for discrete storm modes is highest.

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