SPC AC 131945

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0245 PM CDT Mon Oct 13 2025

   Valid 132000Z - 141200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   AND EVENING ACROSS CENTRAL AND SOUTHEAST AZ...AND LATE TONIGHT OVER
   SOUTH-CENTRAL COASTAL CA...

   ...SUMMARY...
   Isolated, marginally severe hail and wind may occur this afternoon
   and evening over parts of central and southeastern Arizona.  Locally
   damaging winds appear possible late tonight along parts of
   south-central coastal California.

   ...20Z Update...

   ...AZ...
   Southwesterly flow aloft will persist throughout the
   afternoon/evening and overnight. This flow, coupled with modest
   mid-level moisture and buoyancy will promote a continued threat for
   isolated strong thunderstorms, a few of which may be capable of hail
   and/or gusty winds. MCD #2144 was recently issued to address this
   isolated severe potential.

   ...Coastal Central/Southern CA...
   The deep upper low currently just off the northern CA coast will
   continue to progress southward tonight, ending the period just off
   the central CA coast. A strong mid-level jet max will rotate around
   this low as it progresses southward, spreading eastward into
   southern CA late tonight/early tomorrow. A strong frontal band is
   anticipated along the leading edge of the ascent associated with
   this speed max. Current guidance places this band near the coast
   around 05Z/06Z before then moving inland over the next few hours.
   Thermodynamic profiles indicate predominantly shallow convection
   within and ahead of this frontal band, although a few lightning
   flash are possible (most likely within the frontal band itself).
   Additionally, the combination of modest buoyancy and strong
   deep-layer vertical shear could result in rotation within any more
   persistent updrafts, with an attendant threat for damaging gusts
   and/or a brief tornado. Even so, the modest and shallow buoyancy
   should keep updrafts transient, and any rotation within those
   updrafts short lived, keeping the overall severe potential low.

   ..Mosier.. 10/13/2025

   .PREV DISCUSSION... /ISSUED 1045 AM CDT Mon Oct 13 2025/

   ...AZ...
   An upper low currently centered along the OR coast will dig
   southward through the forecast period.  This will maintain deep
   southwesterly flow throughout the Southwest US and Great Basin. 
   Considerable mid-level moisture and marginal CAPE values will
   promote a risk of scattered thunderstorms across these areas through
   tonight.  While an isolated strong storm will be possible over a
   broad region, parts of the central and southeast AZ appear to have
   the best combination of daytime heating, orographic ascent, and
   vertical shear to promote a risk of a few strong/severe storms
   capable of hail and gusty winds.

   ...Coastal CA...
   A strong mid-level jet max will rotate inland tonight into parts of
   south-central coastal CA, along with an associated surface cold
   front.  Forecast soundings along/ahead of the front show sufficient
   CAPE and vertical shear for a risk of a few low-topped but strong
   storms capable of damaging wind gusts or perhaps a tornado.  The
   main concerns will be after midnight.

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