SPC AC 190556

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1256 AM CDT Sun May 19 2024

   Valid 191200Z - 201200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS IN SOUTHWEST TO
   CENTRAL KS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SEPARATELY IN
   EAST-CENTRAL TO SOUTHEAST FL...

   ...SUMMARY...
   Severe thunderstorms are expected across parts of Kansas into
   northwest Oklahoma from late afternoon into mid-evening, including
   the potential for a derecho. Destructive wind swaths of 80-100 mph
   may occur, with localized extreme gusts exceeding 100 mph possible.
   Very large hail and a few tornadoes are also anticipated.

   ...KS/OK vicinity...
   An active severe-weather day is expected during the late afternoon
   to mid-evening. Primary changes this outlook are to increase wind
   and hail probabilities with above-average guidance agreement
   regarding the likelihood of supercells evolving into multiple linear
   bows. Significant severe, from both hail and especially wind,
   appears likely. How far downstream higher-end intensity threats will
   persist towards the lower plains is more uncertain. 

   General thunderstorm activity is expected to be ongoing within a
   low-level warm theta-e advection regime across parts of the central
   Great Plains. This will probably persist through much of the morning
   into the afternoon, becoming more centered on the Mid-MO Valley to
   Upper Midwest. Pronounced differential boundary-layer heating is
   expected between this early-day activity and full insolation that
   yields hot surface temperatures across the southern High Plains.
   With a plume of mid to upper 60s surface dew points overspreading
   much of western/central OK into central KS, beneath a plume of very
   steep mid-level lapse rates, a strongly unstable airmass will
   develop with MLCAPE of 2500-3500 J/kg becoming common.

   A strengthening upper-level jet across the Southwest, nosing over
   the southern Rockies, should aid in dryline sharpening by late
   afternoon. Initial very high-based thunderstorms should form off the
   Raton Mesa behind the dryline, while other storms form along the
   dryline near the TX Panhandle/western OK border, and in the
   north-central KS vicinity near the warm front. The far southern
   dryline storms in northwest OK and near the warm front in KS should
   remain semi-discrete longer, and will be most capable of producing
   very large hail and a couple tornadoes. Between these two corridors,
   CAM signals are fairly consistent that a mix of outflow-dominated
   clusters with embedded supercells will move east-northeast during
   the evening. This includes evolution into linear bowing segments
   with forecast soundings, indicating potential for intense
   rear-inflow jet development. Given the highly favorable
   thermodynamic environment, coupled with the impinging of a mid-level
   jetlet across the southern High Plains, this scenario appears
   probable. 

   The southern to central Great Plains low-level jet will strengthen
   during the evening, which should result in a large MCS with embedded
   bowing structures persisting after dusk. CAM guidance is fairly
   quick to indicate diminishing intensity as MLCIN rapidly increases
   across much of OK into at least southeast KS. But given the
   potential for prolific, organized severe wind swaths upstream, have
   increased severe probabilities downstream from the Mid-MO Valley and
   deeper into OK.

   ...Western NE to western/central SD...
   Scattered thunderstorm development is expected along the northern
   portion of the dryline during the late afternoon to early evening as
   a narrow plume of mid to upper 50s surface dew points spreads north.
   With a more confined and more modestly buoyant warm-moist sector
   relative to KS southward, overall threat should consist of isolated
   to scattered large hail and severe wind.

   ...FL...
   Scattered afternoon thunderstorms appear likely to develop ahead of
   a slow-moving, positive-tilt shortwave trough over the Southeast.
   Best potential for a few supercells should be focused along the
   Atlantic Coast sea breeze across parts the central to south
   peninsula. Favorable deep-layer shear, in conjunction with large
   buoyancy, should foster a predominant threat of large hail, with
   isolated damaging winds possible as well.

   ..Grams/Bentley.. 05/19/2024

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