SPC AC 130548

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1248 AM CDT Mon Jul 13 2020

   Valid 131200Z - 141200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EASTERN
   COLORADO AND NORTHWEST KANSAS INTO CENTRAL NEBRASKA...

   ...SUMMARY...
   Severe thunderstorms are possible from the central High Plains into
   parts of the Upper Midwest this afternoon into tonight.  Severe
   gusts, possibly significant, large hail and a couple of tornadoes
   are the threats with the stronger storms.

   ...Synopsis...
   A mid-level shortwave trough initially over WY/MT at daybreak will
   move through the base of a larger scale trough and reach the Red
   River Valley of the north by late afternoon and subsequently into
   northwest Ontario overnight.  Farther east, a mid-level ridge will
   move east into the Great Lakes while a larger scale trough moves
   from the East Coast into the western Atlantic during the period.  

   At the surface, a cool front will push east across much of the
   Dakotas during the day with the trialing portion of the boundary
   arcing southwestward into the central High Plains to an area of weak
   low pressure.  A lee trough/dryline will extend southward into the
   south-central High Plains.  

   ...Central High Plains...
   Strong heating will steepen low-level lapse rates and models are
   suggesting storm initiation by the early afternoon across southern
   WY and the high terrain of northern CO.  Isolated to scattered
   storms will develop/spread east into the central High Plains during
   the afternoon from the NE Panhandle southward into northeastern NM. 
   The southern fringe of strong mid-level flow will encompass areas
   generally near and north of I-70.  Forecast soundings show very
   steep surface to 500mb lapse rates on the western periphery of a
   moisture reservoir over KS/NE.  Supercells and severe multicells
   capable of large to very large hail will initially be the threat
   before additional storm development/upscale growth into several
   broken bands of storms. Large CAPE (2000-4000 J/kg MLCAPE), very
   steep tropospheric lapse rates, a wind profile for organized storms,
   and a linear mode evolving all suggest the potential for a swath of
   severe gusts (60-80 mph) potentially evolving across the central
   High Plains during the late afternoon/evening. 

   ...Eastern Dakotas into western Wisconsin...
   Strengthening southerly low-level flow will contribute to the
   advection of a moist boundary layer into the Upper Midwest during
   the day.  Scattered thunderstorms are forecast during the mid to
   late afternoon.  The strength of the low- to mid-level flow will
   favor supercell development with the stronger storms as they mature
   in the moist/unstable sector.  Appreciable low-level shear (200
   m2/s2 0-1 km SRH) and moist low levels imply a few tornadoes are
   possible with the more intense mesocyclones.  Models suggest a
   cluster or two will evolve with damaging gusts transitioning towards
   the primary hazard with time.

   ...Eastern OK into western LA...
   A remnant MCV owing to thunderstorm activity this morning across OK
   may focus a risk for thunderstorms this afternoon near residual
   outflow over eastern OK/Arklatex region.  Although predictability is
   low at this time, it appears some risk for a cluster or two may
   evolve from southeast OK into western LA during the day within a
   moist/unstable axis.  Isolated damaging gusts will be the main
   threat with these storms before this potential activity weakens by
   early evening.

   ...New England southward through the Carolinas...
   Scattered thunderstorms are forecast during the midday into the
   afternoon across southern New England.  Some multicellular storm
   organization may lead to a risk for damaging gusts.  Farther south,
   it appears storm coverage is in question across parts of the
   Mid-Atlantic states.  It appears another area of greater storm
   coverage and potential for isolated damaging gusts may evolve within
   a very moist airmass across parts of the eastern Carolinas during
   the afternoon with this activity diminishing by the early evening.

   ..Smith/Lyons.. 07/13/2020

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