SPC AC 112000

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0200 PM CST Sat Mar 11 2023

   Valid 112000Z - 121200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   EASTERN OKLAHOMA INTO NORTHERN MISSISSIPPI...

   ...SUMMARY...
   Scattered severe thunderstorms, capable of large to very large hail,
   will remain possible this evening and overnight across eastern
   Oklahoma into Arkansas.

   ...20Z Update...
   The primary change to this outlook was to expand the Slight Risk
   farther east into northern MS for tonight. Some of the latest
   high-resolution guidance have been trending upwards in intensity of
   a bowing segment of convection originating from earlier supercells
   across AR. After 06Z, this line of storms may progress across
   northern MS with a threat of damaging gusts.

   The severe hail threat remains on track across eastern OK into
   western AR for this evening. Multiple hail producing supercells are
   likely, and a few instances of up to baseball sized hail is
   possible. The primary limiting factor to a more widespread severe
   hail threat is the potential for a rapid upscale growth of storms,
   which may occur after storms achieve supercell status, hence
   limiting the coverage of significant-severe hail.

   Another change to the outlook was to add a Category 1/Marginal Risk
   for portions of the central valley region of CA. Current
   observations depict upper 50s to low 60s F surface dewpoints amid
   warming surface temperatures. Continued diurnal heating will foster
   a well-mixed but moist boundary layer and associated steep low-level
   lapse rates. Forecast soundings depict elongated, mostly straight
   hodographs, suggesting transient, low-topped supercells would be the
   primary mode of convection. Some guidance also hints at relatively
   high amounts of low-level vertically oriented vorticity co-located
   with the better surface-based buoyancy. As such, low-level
   stretching with the more persistent supercells may support a brief
   tornado threat. The best chance for severe will be in the 21-01Z
   time frame.

   ..Squitieri.. 03/11/2023

   .PREV DISCUSSION... /ISSUED 1030 AM CST Sat Mar 11 2023/

   ...OK-TX into the lower MS Valley...
   Located to the south of a more pronounced mid-level low over the
   northern Great Plains, a low-amplitude disturbance embedded within
   strong westerly flow, will move from the central High Plains to the
   Ozarks/OH Valley during the period.  Visible satellite imagery this
   morning shows an extensive stratus shield/moist sector over eastern
   OK/TX into AR/LA.  As a warm front advances north during the day
   into eastern OK/AR, a low will develop east across the Red River
   Valley while a cold front progresses southeast across OK and a
   dryline sharpens over north TX.  

   Steep 700-500 mb lapse rates were observed on 12z raobs over the
   southern Great Plains (7.9 deg C/km at Norman, OK).  Gradual cooling
   temperatures in the mid-levels will overspread a destabilizing warm
   sector this afternoon.  Forecast soundings show an initial capping
   inversion gradually weakening by late afternoon with temperatures
   warming into the 80s along the dryline portion of the overall risk
   area.  Ample deep-layer shear will favor supercells with the initial
   storms.  Model guidance continues to show scattered thunderstorms
   initially developing over eastern OK this evening and spreading east
   into AR during the evening and into the overnight.  Some upscale
   growth into a mix of supercells and linear structures is indicated
   by the models.  The predominant risk will be large to very large
   hail with the mostly elevated activity.  A gradual weakening is
   expected as storms eventually move into northern MS late tonight as
   buoyancy lessens with east extent.  

   Farther south along the dryline, convective initiation is still
   uncertain across north TX.  Models continue to show a limited
   probability for storm initiation across this corridor.  Nonetheless,
   if a storm or two were to develop and become sustained, a severe
   risk could materialize for a few hours. 

   ...Southwest States and CA...
   A belt of strong/low-amplitude westerlies coupled with steep lapse
   rates and modest moisture could yield a couple of stronger storms
   late this afternoon/early evening across the California San Joaquin
   Valley and/or across southern Nevada into southern Utah/far northern
   Arizona. However, organized severe storms are not currently
   expected.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z