SPC AC 190600

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CDT Sun Jul 19 2020

   Valid 201200Z - 211200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE DAKOTAS...

   ...SUMMARY...
   At least isolated severe storms capable of producing both large hail
   and damaging winds appear possible Monday across parts of the
   Dakotas. Other strong to severe storms may occur over portions of
   New England into the Mid-Atlantic, and from the mid Mississippi
   Valley into the central Plains.

   ...Northern Plains...
   A shortwave trough embedded within quasi-zonal flow across the
   northern tier of the CONUS should move east-southeastward across the
   northern Plains on Monday. Low-level moisture is forecast to remain
   fairly limited by mid July standards across this region, with
   surface dewpoints generally expected to increase only into the upper
   50s to lower 60s F. A weak surface low may accompany the shortwave
   trough, and storms are expected to form by Monday afternoon across
   the western Dakotas along a surface trough/weak front. Mid-level
   west-northwesterly flow of 30-40 kt should support similar values of
   effective bulk shear. A mix of multicells and supercells may occur
   in this regime, with weak to locally moderate instability (MLCAPE
   1000-2000 J/kg) adequate for maintenance of strong to severe storms.
   Isolated large hail and damaging wind gusts should be the main
   threats through at least early Monday evening. The overall risk
   should gradually lessen with eastward extent across the Dakotas
   Monday night. Eventual evolution of storms into a bowing complex
   appears possible into parts of western/central NE Monday night, but
   this potential still appears very uncertain. 

   ...Mid Mississippi Valley into the Central Plains...
   Convection will likely be ongoing at the start of the period in a
   weak low-level warm advection regime across parts of the central
   Plains (most likely eastern KS/western MO and vicinity). It appears
   possible that modest enhancement to the mid-level flow due to an MCV
   emanating from these morning storms may encourage some storm
   organization across the mid MS Valley later in the day. There is
   substantial spread in the location of this possible redevelopment.
   Still, both isolated damaging winds and marginally severe hail may
   occur given the moderate to locally strong instability and modest
   deep-layer shear that should be present. This severe risk should
   quickly wane Monday evening with the loss of daytime heating.
   Farther west over the central High Plains, storms that initially
   form over the higher terrain of central WY and north-central CO
   should spread eastward and eventually encounter greater instability.
   An isolated severe risk may occur with this activity as well.

   ...New England into the Mid-Atlantic...
   An upper trough will move east-northeastward across eastern Canada
   and the Northeast on Monday. A surface cold front is likewise
   forecast to shift east-southeastward across the Northeast and
   Mid-Atlantic through the day. Diurnal heating of a moist low-level
   airmass ahead of the front should steepen low-level lapse rates, and
   support the development of generally 1000-2000 J/kg of MLCAPE by
   Monday afternoon. Modestly enhanced mid-level flow will foster
   around 20-30 kt of effective bulk shear, sufficient for mainly
   multicells and small clusters. There is some concern that with the
   stronger large-scale forcing remaining displaced to the north of the
   warm sector, convection may struggle to initiate along the trailing
   cold front. Still, there remains enough of a convective
   precipitation signal in global guidance to support the continuation
   of the Marginal Risk for strong to locally damaging wind gusts. Any
   storms that form should move offshore by early Monday evening,
   ending the severe risk.

   ..Gleason.. 07/19/2020

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