SPC AC 132017

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0317 PM CDT Mon Jun 13 2022

   Valid 132000Z - 141200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF FAR SOUTHERN LOWER MICHIGAN INTO NORTHEAST INDIANA AND WESTERN
   OHIO...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
   THE NORTHERN PLAINS...

   ...SUMMARY...
   Scattered severe thunderstorms are expected across parts of the
   northern Plains, and from portions of the Midwest into the Great
   Lakes and Ohio Valley. Large hail, damaging winds, and a few
   tornadoes are possible. Some of the winds could be significantly
   severe (75+ mph) across parts of the Midwest/Ohio Valley this
   afternoon and tonight.

   ...20Z Update...
   Portions of the Ohio Valley have been upgraded to a Moderate Risk
   for the anticipation of a highly organized MCS/possible Derecho
   developing from a supercell structure across southern WI. Despite
   the lack of agreement in high-resolution guidance, this supercell is
   traversing a strong buoyancy gradient (with extreme MLCAPE values
   exceeding 5000 J/kg noted in the OH Valley). In addition, 40+ kts of
   effective bulk shear are also present along the buoyancy gradient,
   which expands across a long west-east corridor over northern
   portions of the OH Valley. Expectations are for this supercell
   (which already shows an intense RFD surge per latest KMKX radar
   data) to eventually become more outflow dominant, generating a
   strong cold pool preceded by the extreme instability. Upscale growth
   with the cold pool would support an expanding MCS traversing a
   CAPE/shear parameter space typically associated with bow
   echoes/derechoes. In addition, multicells continue to percolate
   across central IN amid an extremely unstable environment (i.e. 5000+
   J/kg MLCAPE per 18Z mesoanalysis) and an appreciable severe wind
   threat could develop with this cluster as well should upscale growth
   occur.

   A significant wind area has been added to portions of the Slight
   Risk across portions of central into northern South Dakota. Here,
   the potential exists for an HP supercell/short bowing segment to
   manifest from earlier storms along or immediately behind the surface
   cold front somewhere within the 03-06Z period (especially in the
   12-18Z runs of the HRRR) and traverse an axis of high-end elevated
   buoyancy (i.e. 4000 J/kg MUCAPE driven by 9 C/km deep-layer lapse
   rates). Should this scenario unfold, 75+ mph gusts may occur in
   addition to 2+ inch hail. Consideration was considered for an
   upgrade to a Category 3/Enhanced. However, the localized
   nature/expected limited coverage of the higher-end severe threat
   precludes an upgrade. Please see MCD #1144 for short-term severe
   concerns across the northern Plains.

   ..Squitieri.. 06/13/2022

   .PREV DISCUSSION... /ISSUED 1204 PM CDT Mon Jun 13 2022/

   ...Midwest/Great Lakes...
   A consequential potential for impactful storms exists today into
   tonight across the region, potentially including long-lived/intense
   MCS development, owing to a high degree of moisture and extreme
   potential instability. However, short-term uncertainty remains high
   regarding spatial details exists owing to a strong capping
   inversion, along with guidance variability in terms of
   timing/spatial differences.

   Multiple MCVs, albeit generally weakening, are still readily
   apparent at late morning across portions of Iowa/southern Minnesota
   into western Wisconsin. Regional WSR-88D VWP data features notably
   enhanced mid-level winds, particularly by mid-June standards, within
   this same regional corridor (for example, 50-60 kt winds 3-6 km AGL
   recently noted at KDMX/Des Moines).

   12z upper-air analysis in conjunction with more contemporary GPS PW
   values reflects a moisture-rich corridor particularly from eastern
   Iowa and much of Illinois southeastward into southern Indiana. A
   considerable elevated mixed layer extends east-northeastward atop
   this moisture, highlighted by a 14.6 C temperature at 700 mb per 12z
   ILX/Lincoln, IL observed sounding. 

   Given the notable mid-level warmth, storm development later this
   afternoon into evening will tend to favor areas near/immediate cool
   side of a northward-shifting warm front across the region. This
   would favor development across southern Wisconsin into northern
   Indiana/Lower Michigan and Ohio. One potential exception could be
   across downstate areas of eastern Illinois into Indiana, where
   glancing MCV-related ascent (reference ongoing mid-level convection
   near/west of the Mississippi River this morning) could interact with
   a very moist/unstable and weakly inhibited boundary layer downstream
   highlighted by surface dewpoints generally in the upper 70s F. 

   Where storms do regionally develop, large hail and damaging winds
   can be expected, along with at least some potential for tornadoes
   with surface-based storms developing near/interacting with the warm
   front. 

   An upgrade to Moderate Risk may still be warranted across parts of
   the region (particularly Lower Michigan, northern Indiana and/or
   Ohio) pending subsequent observational trends and increased
   confidence in a preferred sub-regional corridor of intense storm
   development.

   ...Dakotas...
   Influenced by the approaching upstream upper trough, a surface low
   is forecast to deepen over eastern Wyoming this afternoon while a
   cold front moves across the northern Rockies and High Plains.
   Thunderstorms are expected to form along the front by early evening
   over western South Dakota/North Dakota and track northeastward.
   Vertical shear profiles will be favorable for supercell storms
   capable of all hazards, particularly along and on the immediate cool
   side of the boundary.

   ...Southern/central High Plains...
   Modest moisture and a hot/deeply mixed boundary layer could support
   a few severe-caliber wind gusts if/where storms develop late this
   afternoon/early evening.

   ...Maine...
   Influenced by modest buoyancy and moderately strong winds aloft on
   the periphery of an upper low over Quebec, a few strong to severe
   thunderstorms may occur this afternoon across the region.

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