Weather discussion outlook

[WeatherWheeler35]

  SPC AC 201948
  Day 1 Convective Outlook NWS Storm Prediction Center Norman OK  0248 PM CDT Sat May 20 2023
  Valid 202000Z - 211200Z
  ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS  OF THE NORTHWEST...THE RIO GRANDE VALLEY AND THE DEEP SOUTH...
  ...SUMMARY...  Isolated and marginally severe thunderstorms are possible through  this evening across parts of the Deep South, the Northwest, and the  Rio Grande Valley.
  ...20z Update...
  Only minor adjustments have been made to the Marginal risk (level 1  of 5) across Deep South Texas and MS/AL. These changes are based on  currently location of ongoing convection and the position of the  surface cold front. Otherwise, the previous forecast is on track.  For more details, see the 1630z Day 1 discussion below.
  ..Leitman.. 05/20/2023
  .PREV DISCUSSION... /ISSUED 1126 AM CDT Sat May 20 2023/
  ...Deep South...  A low-amplitude shortwave trough over the Mid-MS Valley will move  southeast towards the southern Appalachians, and will be preceded by  an MCV currently centered on middle TN. Abundant cloud coverage  across northern portions of AL/GA will limit boundary-layer  destabilization to the immediate southeast of lingering stratiform  rain attendant to the MCV. Amid poor mid-level lapse rates (5-5.5  C/km between 700-500 mb) sampled by the 12Z BMX/BNA soundings, the  lack of more robust boundary-layer heating will likely mitigate  appreciable severe potential with north/east extent.
  With more robust insolation underway farther south-southwest and  richer boundary-layer moisture, a plume of moderate MLCAPE from  1500-2000 J/kg is anticipated across southern MS to central AL. This  should support convective development trailing southwestward  along/ahead of a southeast-moving cold front in the next few hours.  With a predominant westerly deep-layer wind profile, effective bulk  shear should be limited to around 20-25 kts where buoyancy is  greater. Given the poor mid-level lapse rates upstream, hail sizes  will probably remain small to marginally severe. A threat for  isolated damaging winds should be the main hazard with multicell  clusters that spread east-southeast and largely weaken after sunset.
  ...OR/WA...  Somewhat greater convective coverage is anticipated relative to  yesterday during the late afternoon and evening within a modest  south-southwesterly deep-layer flow regime. The most likely corridor  for scattered storm development is off the higher terrain in  southern OR east of the Cascades, with more isolated activity  possible across central WA. Where adequate effective bulk shear is  present, largely close to the Cascades, marginally severe hail will  be possible. Otherwise, isolated strong gusts will be possible in  eastern OR given deeper mixed thermodynamic profiles with eastern  extent. 
  ...Southwest NM vicinity...  A minor upper low persists near the northwest Sonora/southeast AZ  border area and will drift north-northeast today. With low 50s  surface dew points having spread west of the Rio Grande following a  recent cold front intrusion, a pocket of weak buoyancy should  develop with MLCAPE of 500-1000 J/kg. Effective bulk shear will  likely remain weak, from only 20-25 kts as stronger speed shear is  confined to the very upper portion of the buoyancy profile. Small to  marginally severe hail and a few locally strong gusts cannot be  ruled out.   ...Deep South TX...  A few strong storms remain possible later this afternoon as a cold  front continues to move slowly southward. Buoyancy should remain  moderate owing to broken cloud coverage ahead of the front. 0-6 km  winds will remain unremarkable with moderate southwesterlies above  that. In addition, mid-level lapse rates peaked this morning and are  consistently progged to weaken through the day. Small to marginally  severe hail and a few locally strong gusts cannot be ruled out.
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  NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z