SPC AC 091955

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0255 PM CDT Tue May 09 2017

   Valid 092000Z - 101200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   SOUTHEAST NEW MEXICO AND WEST TEXAS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OUTSIDE OF THE
   ENHANCED RISK AREA ACROSS PARTS OF THE SOUTHERN AND CENTRAL HIGH
   PLAINS INTO THE SOUTHERN ROCKIES...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OUTSIDE OF THE
   SLIGHT RISK AREA ACROSS PARTS OF THE SOUTHERN AND CENTRAL
   PLAINS...SOUTHERN AND CENTRAL ROCKIES INTO THE FOUR CORNERS
   REGION...

   ...SUMMARY...
   Scattered severe thunderstorms with a threat for tornadoes, large
   hail and damaging winds are expected across parts of eastern New
   Mexico and west Texas late this afternoon through the overnight
   period. Other severe storms with large hail and wind damage could
   occur in parts of eastern Colorado late this afternoon into this
   evening.

   A significant change has been made to the outlook for this issuance.
   An enhanced risk area has been added for parts of southeast New
   Mexico and west Texas. The upgrade includes adding 30 percent hail
   and 10 percent tornado contours.  The latest HRRR run along with the
   deterministic solutions from the NAM and GFS appear reasonable.
   These solutions suggest that several supercells will be possible
   across the enhanced area early this evening. As the low-level jet
   strengthens and maximizes over west Texas this evening, conditions
   will become favorable for large hail and tornadoes. Hailstones of
   greater than 2 inches in diameter may also occur with the stronger
   supercells. For the mid to late evening, the models also suggest
   that a band of severe storms will develop along the western edge of
   the enhanced risk area and move eastward to the Texas state line by
   just after midnight. Because of this second round of severe storms,
   large hail coverage is expected to exceed 30 percent across the
   enhanced area. See MCD 670 for more details.

   ..Broyles.. 05/09/2017

   .PREV DISCUSSION... /ISSUED 1126 AM CDT Tue May 09 2017/

   ...Eastern NM/CO into western KS/TX...
   Only minor changes have been made to the ongoing forecast.  It
   appears two regimes of severe weather will occur today.  The first
   will be associated with thunderstorms that form over/near the
   mountains of north-central NM into southeast CO.  Steep mid level
   lapse rates and continued easterly/upslope flow will result in
   scattered storms beginning early this afternoon.  These storms will
   likely pose a risk of large hail (possibly very large hail) as they
   build northeastward into northeast NM and eastern CO.  An isolated
   tornado or two is also possible with the more intense storms in this
   regime today.  The northern extent of the severe risk will likely be
   delimited by the Denver convergence zone.  These storms may spread
   into western KS and the northern TX Panhandle this evening before
   weakening.

   Later this evening, 12Z guidance is in good agreement that a second
   round of severe storms will develop over parts of southeast NM and
   southwest TX.  These storms are more likely to maintain discrete
   character, with supercells likely.  The storms will track
   northeastward across eastern NM and into parts of west TX
   around/after dark posing a risk of very large hail, damaging winds,
   and a few tornadoes.

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