Severe Weather outlook

• SPC Sep 18, 2024 2000 UTC Day 1 Convective Outlook

  SPC 2000Z Day 1 Outlook
  

  Day 1 Convective Outlook  
  NWS Storm Prediction Center Norman OK
  0254 PM CDT Wed Sep 18 2024
  
  Valid 182000Z - 191200Z
  
  ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
  NORTHEAST NEBRASKA INTO FAR NORTHWEST IOWA...EASTERN SOUTH
  DAKOTA...AND WESTERN MINNESOTA...
  
  ...SUMMARY...
  Thunderstorms capable of producing severe wind gusts and large hail
  are possible today across parts of the eastern Dakotas and Minnesota
  into the mid Missouri Valley. A marginal severe threat will also
  extend southward into parts of the central and southern Plains.
  
  ...20Z Update...
  No changes were made to the ongoing forecast. For mesoscale details
  concerning eastern South Dakota and vicinity, see MCD 2083.
  Additional details can be found in the previous discussion below.
  
  ..Wendt.. 09/18/2024
  
  .PREV DISCUSSION... /ISSUED 1118 AM CDT Wed Sep 18 2024/
  
  ...Northern Plains/Upper Midwest to the Southern High Plains...
  A closed upper low centered over eastern MT will continue
  northeastward during the period, reaching southeast SK by early
  Thursday morning. Upper-level ridging extending northward from the
  northwest Gulf Coast into the upper MS Valley will slowly shift
  eastward to the Upper Great Lakes. A belt of enhanced southwesterly
  mid-level flow will extend from southern CA through the central High
  Plains, while also wrapping cyclonically through the eastern Dakotas
  and into southern Canada. At the surface, a trough/front extends
  southward from central ND into SD and western NE, before continuing
  southwestward over the central/southern High Plains. This boundary
  may serve as a focus for renewed thunderstorm development later
  today.
  
  A band of elevated convection has generally moved northward from
  northeast ND and northwest MN into southern MB. In the wake of this
  activity, cloud cover remains prevalent across much of the warm
  sector across the northern Plains/Upper Midwest. Still, filtered
  daytime heating of an adequately moist boundary layer should aid in
  the development of around 1500-2000 J/kg of MLCAPE by late
  afternoon. Isolated to scattered thunderstorms may form along/east
  of the surface trough/front within a favorable zone of 30-40 kt of
  effective bulk shear. But, better large-scale forcing associated
  with the upper low over the northern High Plains will tend to remain
  displaced north and west (in southern Canada). Accordingly, 12Z
  high-resolution guidance continues to vary regarding storm coverage
  across the Slight Risk (isolated versus scattered) given the weaker
  forcing aloft. Even with this continued uncertainty, various NAM/RAP
  forecast soundings still suggest a somewhat conditional risk for
  organized storms (mix of multicells and supercells). Severe
  hail/wind may accompany the stronger storms from late afternoon
  through early evening, before this activity eventually weakens.
  
  Further south into the central/southern Plains, low-levels are
  forecast to be somewhat drier near the surface trough, with surface
  dewpoints expected to mostly range in the upper 50s to low 60s by
  late afternoon with pronounced boundary-layer mixing. Warmer
  mid-level temperatures and limited large-scale ascent across these
  regions should temper the overall intensity of any updrafts that can
  form and be sustained, and resultant intensity/coverage of this
  convection. Still, some guidance shows locally greater thunderstorm
  coverage and resulting isolated severe wind threat from the eastern
  TX Panhandle into far northwest OK and southern KS during the late
  afternoon/early evening, where low-level lapse rates should be
  maximized with robust daytime heating.
  
  

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