SPC AC 200630

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0130 AM CDT Sun May 20 2018

   Valid 221200Z - 231200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN
   NM AND WEST TX...

   ...SUMMARY...
   Isolated strong thunderstorms are expected across eastern New Mexico
   and west Texas Tuesday afternoon.

   ...Eastern NM/Western TX...

   Upper low that is expected to drift into the lower CO River Valley
   is forecast to weaken and lift northeast into the Great Basin during
   the latter half of the period. As a result, weak height rises are
   expected across the southern High Plains as primary corridor of
   stronger mid-level flow extends across southern AZ into central CO.
   Model guidance suggest strong boundary-layer heating will be noted
   across eastern NM/west TX such that convective temperatures should
   easily be breached by late afternoon. Favorable low-level
   trajectories will maintain adequate moisture across this region for
   ample instability required for robust updrafts. Even so, deep-layer
   shear will be seasonally weak but likely sufficient for isolated
   severe thunderstorms capable of generating hail/wind. This activity
   will be strongly diurnal in nature.

   ...Elsewhere...

   Unusually weak steering currents for mid may are expected to persist
   across much of the CONUS outside of the northeastern US. This flow
   regime leads to low predictability regarding organized severe
   thunderstorms despite the likelihood for isolated severe in various
   locations across the country, primarily east of the Rockies. Late
   evening guidance suggest low-level warm advection may induce deep
   convection across the northern Plains late and conceivably this
   activity could generate some hail.

   Another region where a few severe thunderstorms could evolve will be
   across portions of the OH Valley along the southwestern flank of
   stronger flow associated with a short-wave trough. If adequate
   instability can develop across portions of OH/western PA/western NY
   there is some concern for robust convection. However, predictability
   is just too low at this time to issue severe probabilities.

   ..Darrow.. 05/20/2018

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