SPC AC 151951

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0251 PM CDT Thu Aug 15 2019

   Valid 152000Z - 161200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER CENTRAL
   AND EASTERN KS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
   THE NORTHERN/CENTRAL GREAT PLAINS AND THE NORTHERN MID-ATLANTIC
   STATES INTO PA...

   ...SUMMARY...
   Severe thunderstorms are most likely to be centered on eastern
   Kansas during the late afternoon and evening. Severe hail and wind
   gusts may be significant with a few tornadoes also possible.

   ...20Z Update...

   Overall the forecast remains on track with little change needed.
   Highest severe thunderstorm coverage is still expected to be across
   central/eastern KS later this afternoon and evening. Primary change
   to the outlook is to extend the Slight Risk southeastward across
   eastern VA and into far northeast NC. Recent trends suggest higher
   severe coverage across this region.

   ..Mosier.. 08/15/2019

   .PREV DISCUSSION... /ISSUED 1130 AM CDT Thu Aug 15 2019/

   ...Central/eastern KS vicinity...
   An MCS is ongoing across eastern NE with a trailing composite
   outflow/cold front extending into far northwest KS. Waning low-level
   warm advection through the next few hours should inhibit substantial
   strengthening across the Lower MS Valley. The trailing outflow will
   be the primary focus for late afternoon to early evening
   redevelopment. Low-level convergence should support initial storms
   from north-central into northeast KS. A plume of upper 60s surface
   dew points at present across central KS will be maintained as richer
   boundary-layer moisture advects north from OK, beneath the eastern
   extent of the elevated mixed layer. Ample diabatic heating will
   yield large buoyancy with MLCAPE likely reaching 2500-3500 J/kg. A
   veering wind profile with height will support initial supercells,
   with hodograph enlargement occurring through the evening as a
   southwesterly low-level jet intensifies. The setup should foster a
   risk for very large hail and a few tornadoes. However, the overall
   mode may tend to grow upscale into clusters and an MCS relatively
   quickly given the strengthening forcing for ascent during the
   evening. This may result in the predominant threat becoming severe
   wind gusts (a few of which may be significant) as an MCS develops
   bowing structures across eastern KS towards western MO/northern OK.
   Overall severe threat should subside overnight with the most likely
   MCS track approaching the Ozark Plateau. 12Z non-HRRR HREF members
   are more consistent with this overall scenario than recent HRRR
   runs, with the parent RAP maintaining more pronounced MLCIN in much
   of the warm sector. Nevertheless, an Enhanced Slight Risk appears
   warranted given the potential for a higher-end intensity/coverage
   scenario.

   ...SD vicinity...
   A low-amplitude shortwave trough and attendant surface boundary will
   move east across the Dakotas. Ample diabatic heating is underway
   downstream across central to eastern SD north of the NE MCS.
   Presence of upper 50s to low 60s boundary-layer dew points will
   support MLCAPE of at least 1500-2000 J/kg. While low-level shear
   will be weak, robust speed shear from 700 mb on up will foster an
   elongated mid/upper-level hodograph favorable for mid-level rotation
   and an eventual eastward-progressing MCS with potential for a brief
   bow. Initial large hail transitioning to predominant severe wind
   gusts should be the main threats before activity weakens in western
   MN.

   ...Eastern WY and NE Panhandle...
   Residual low-level moisture (corridor of upper 50s surface dew
   points) within a weak upslope regime north of the trailing composite
   outflow/cold front over northeast CO will support a conditional
   supercell environment favorable for large hail. However, storm
   coverage appears likely to be rather isolated at peak heating in the
   wake of the shortwave trough crossing the Dakotas. Greater
   confidence in storms exists early Friday morning ahead of the next
   upstream shortwave impulse.

   ...Eastern OH and PA vicinity...
   A low-amplitude upper trough from eastern Lake Superior to western
   OH will gradually move east with an attendant weak surface cyclone 
   drifting across northern OH. Relatively cool temperatures aloft atop
   a plume of mid to upper 60s surface dew points should result in
   MLCAPE reaching 1500-2000 J/kg during the next few hours. Though
   low-level flow/shear will be weak, there will be sufficient
   deep-layer vertical shear for multiple mid-level rotating updrafts
   as scattered storms develop from the Upper OH Valley/Lower Great
   Lakes regions across the lee of the Appalachians. Convection should
   remain predominantly discrete, yielding a risk for both severe hail
   and damaging winds, with these threats waning after dusk.

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