SPC AC 310558

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1258 AM CDT Fri Jul 31 2020

   Valid 311200Z - 011200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHERN PLAINS...ARKLATEX...LOWER TO MID MISSISSIPPI VALLEY AND
   MID-ATLANTIC...

   ...SUMMARY...
   Thunderstorms associated with marginally severe wind gusts and hail
   will be possible across the southern Plains. Other storms with
   strong wind gusts will be possible from the Arklatex into the
   Tennessee Valley and across the Mid-Atlantic.

   ...Southern Plains/Arklatex/Lower to Mid Mississippi Valley...
   An upper-level trough will move southeastward into the Arklatex
   today. At the surface, a low will move across the Mid Mississippi
   Valley as an attendant cold front advances southeastward into the
   Arklatex and Texas Hill Country. Along and south of the front, a
   very moist airmass will be in place with dewpoints generally in the
   lower to mid 70s F. In response to surface heating, moderate
   instability is expected by afternoon across much of the moist
   sector. Thunderstorms appear likely to first develop around midday
   just ahead of the upper-level trough from east Texas across southern
   Arkansas, northern Louisiana and into northern Mississippi. This
   activity could have a wind-damage threat due the moderate
   instability and steep low-level lapse rates. Deep-layer shear
   generally below 30 kt should keep the severe threat marginal.

   Further to the southwest, across the Texas Hill country, moderate
   instability should also be in place along and ahead of the front by
   early afternoon. Although large-scale ascent is forecast to be weak,
   low-level convergence along the front could be strong enough for
   isolated convective initiation. The instability combined with steep
   mid-level lapse rates could be enough for hail and strong wind gusts
   during the mid to late afternoon.

   ...East-central New Mexico...
   North-northwest mid-level flow will be in place today across the
   Rockies and High Plains. At the surface, a post-frontal airmass
   across much of the southern High Plains and southern Rockies will
   become moderately unstable by afternoon. Convection will first
   initiate in the higher elevations of north-central New Mexico during
   the early afternoon with this convection gradually spreading
   southward across east-central New Mexico. In addition to moderate
   instability (MLCAPE of 1000 to 2000 J/kg), model forecasts have 0-6
   km shear generally in the 25 to 35 kt range across much of
   east-central New Mexico today. This combined with steep mid-level
   lapse rates will support a risk for hail and marginally severe wind
   gusts with the stronger storms.

   ...Mid-Atlantic...
   West-southwest mid-level flow will be in place today from the
   southern Appalachians northeastward into the Mid-Atlantic. At the
   surface, a low near Delaware will move offshore as a cold front
   advances southward across Virginia. Surface dewpoints to the south
   of the front will be in the mid to upper 70s F, resulting in the
   development of moderate instability by afternoon. Thunderstorms are
   expected to initiate during the afternoon along the front and move
   eastward across central and eastern Virginia. In addition to
   moderate instability, veered wind profiles and steep low-level lapse
   rates may enable the stronger cells to have a marginal wind-damage
   threat during the afternoon.

   ...Northern High Plains...
   Northwest mid-level flow will be in place across the northern High
   Plains today. A subtle shortwave trough is forecast to move
   southeastward into eastern Montana this afternoon. At the surface, a
   corridor of low-level moisture will be located from northern Montana
   extending east-southeastward into far western North Dakota. A pocket
   of moderate instability may develop along this corridor by early to
   mid afternoon. Some model solutions have thunderstorms forming along
   the northern edge of the stronger instability and moving
   southeastward into eastern Montana by mid to late afternoon. If this
   scenario unfolds, then deep-layer shear should be strong enough for
   a marginal hail and wind-damage threat.

   ..Broyles/Wendt.. 07/31/2020

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