2024/04/15 - Early Morning Look At Today's Severe Risk

8:00 AM CDT - A complex forecast is unfolding across the Plains today as a strong storm system approaches the region. I wanted to share my thoughts on the situation. A strong capping inversion will likely suppress severe storm development for much of the day, despite a favorable environment. The exception appears to be Northwest Texas where several high resolution models show a couple supercells developing by late afternoon. Stronger surface heating is expected across this area compared to areas farther north. Any storms that develop would have the potential to produce Quarter to Baseball-size Hail, Damaging Winds of 60-75 mph, and a couple Tornadoes. Activity would begin to wane by early evening as it encounters a less favorable environment to the east. Attention then turns back toward the west, near the dryline.

With an increasing low-level jet this evening, the environment will become even more favorable for supercells into the overnight hours. The main uncertainty/limiting factor is the capping inversion. My current thinking is that increasing lift and forcing from the west will be enough to erode the cap for at least widely scattered severe storms. I drew up three graphics this morning to better illustrate my thoughts. The green line depicts a Marginal Risk, the yellow line depicts a Slight Risk, and the orange line depicts an Enhanced Risk.

I have an Enhanced Risk from Northwest Texas into West Central Oklahoma this evening, shifting it northeastward overnight and into the early morning hours on Tuesday. This is based on the thinking that the cap will erode enough for development this evening. Any storms that develop will be capable of Quarter to Baseball-size Hail, Damaging Winds of 60-75 mph, and Tornadoes. The environment will be supportive of a Strong Tornado with any intense supercell. That said, the overall risk appears low/very conditional at this time. This could change in later updates today.

Lastly, I have attached this morning's official SPC Outlook below, along with their discussion copied straight from their website. I will post additional updates later today, so stay tuned.

SPC AC 151245

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0745 AM CDT Mon Apr 15 2024

   Valid 151300Z - 161200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE CENTRAL PLAINS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHERN MID-ATLANTIC...

   ...SUMMARY...
   Scattered severe thunderstorms are likely across parts of the Great
   Plains, beginning mainly this evening and continuing overnight.
   Several tornadoes, large to very large hail, and damaging wind gusts
   all appear possible. Strong tornadoes may occur this evening across
   parts of Kansas and Nebraska.

   ...Synopsis...
   A large, closed upper cyclone is present over the Great Basin this
   morning. This feature will track eastward across the central
   Rockies, eventually ejecting over the southern/central Plains
   tonight. A strong mid/upper-level jet attendant to this upper
   cyclone will overspread much of the southern/central Plains through
   this evening. Pronounced large-scale ascent preceding the
   upper-level trough/low will encourage additional deepening of a
   surface low over the central High Plains though the day. Moisture
   will continue streaming northward through the period in tandem with
   a warm front and persistent low-level warm/moist advection. This
   warm front should be located across NE and perhaps into far southern
   SD by late this evening, as the primary surface low consolidates
   over the NE Panhandle. A dryline is forecast to mix eastward across
   the southern/central High Plains through peak afternoon heating,
   before retreating westward this evening across parts of the TX/OK
   Panhandles and western KS.

   ...Northern/Central Plains (Kansas/Nebraska/South Dakota)...
   A cap and the late timing of large-scale ascent associated with the
   ejecting upper cyclone will likely inhibit convective development
   across the northern/central Plains through at least late afternoon.
   Still, low-level moisture will gradually increase through the day,
   with surface dewpoints of at least upper 50s to low 60s becoming
   common by early this evening across the warm sector. Steep mid-level
   lapse rates and cooling thermal profiles aloft are expected to
   contribute to substantial MLCAPE by the peak of the diurnal heating
   cycle, with values likely ranging around 2000-3000 J/kg. With
   gradually strengthening mid/upper-level flow anticipated, deep-layer
   shear should also become sufficiently strong to support a mix of
   supercells and multicells across this region.

   Convective initiation should be delayed across much of KS/NE/SD
   until around 00Z as a southerly low-level jet rapidly strengthens to
   50-60 kt. Very large hail (around 2-3 inches in diameter) will be a
   threat with any supercells that can form along/near the warm front,
   or southward along the length of the dryline into western KS.
   Low-level hodographs are forecast to become enlarged/curved in the
   00-06Z time frame tonight, and the threat for tornadoes is likewise
   expected to increase with any supercells that can persist and remain
   at least semi-discrete. Confidence has increased in a more
   concentrated corridor of tornado potential across parts of
   western/central KS into central NE, where supercells appear most
   likely in very favorable thermodynamic and kinematic parameter
   space. Given the forecast strength of the low-level shear, strong
   tornadoes appear possible this evening/tonight across this area.
   Severe/damaging winds will also be possible as convection attempts
   to grow upscale into one or more clusters overnight. Even with
   nocturnal cooling, these severe/damaging winds may persist given the
   ample reservoir of buoyancy available.

   ...Southern Plains (Oklahoma/Texas)...
   The overall coverage and severity of convection across the southern
   Plains is somewhat more uncertain compared to locations farther
   north across the central Plains. This uncertainty is largely tied to
   the influence of a sub-tropical mid/upper-level jet that will move
   over the southern Plains through the period, along with associated
   mid/upper-level cloudiness. These clouds may tend to limit daytime
   heating to some extent along the length of the dryline. Even so,
   attempts at robust convective development will probably occur across
   parts of northwest TX by late this afternoon. If this activity can
   be sustained, then supercells appear likely given ample (50-60 kt)
   deep-layer shear. Isolated large to very large hail will probably be
   the main threat with this convection as it moves towards
   north-central TX. But, occasional severe/damaging winds and perhaps
   a couple of tornadoes may also occur through the early evening. Most
   guidance indicates any supercells which develop will weaken with
   eastward extent as they encounter increasing MLCIN, and become
   increasingly displaced from the better large-scale ascent with the
   upper trough/low ejecting over the central Plains. A highly
   conditional severe threat remains apparent across OK late this
   afternoon and evening, with a favorable parameter space to support
   supercells capable of producing all severe hazards. But, much of OK
   may have a relative minimum in convective activity until late
   tonight as a Pacific cold front overtakes the dryline.

   ...Mid-Atlantic to the Mid Mississippi Valley...
   The glancing influence and modest ascent with an upper trough across
   the Northeast and eastern Canada will overspread parts of the
   Mid-Atlantic by early afternoon. Weak low-level convergence along a
   sagging cold front should be sufficient to support isolated to
   scattered thunderstorm development through the afternoon and evening
   from parts of the mid MS Valley into the OH Valley, central
   Appalachians, and southern Mid-Atlantic. Ahead of the front across
   the Mid-Atlantic, generally low 50s surface dewpoints and steepened
   mid-level lapse rates will foster around 1000-1500 J/kg of MLCAPE
   with moderately enhanced westerly mid/upper-level flow. Deep-layer
   shear across this region appears strong enough to support supercells
   with an associated threat for large hail. Damaging wind gusts may
   also occur with multicell clusters that attempt to form as they
   track generally east-southeastward through the evening hours. With
   weaker deep-layer shear across the mid MS and OH Valleys, convection
   should be somewhat less organized while still posing an isolated
   threat for hail/wind. The overall severe threat should gradually
   diminish through late evening with the loss of diurnal heating.

   ..Gleason/Grams.. 04/15/2024