SPC AC 261946

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0246 PM CDT Wed Mar 26 2025

   Valid 262000Z - 271200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS WESTERN
   PORTIONS OF WASHINGTON AND OREGON...

   ...SUMMARY...
   Severe thunderstorms are expected across parts of the Pacific
   Northwest this afternoon and evening, with supercells possible west
   of the Cascades across Oregon into Washington. These storms may
   produce large hail, perhaps a tornado or two, and severe wind gusts.

   ...20z Update...
   Only minor adjustments were needed to removed thunder across
   southern OK/northern TX with this update. The Slight risk across the
   Northwest and Marginal Risk in south Texas were unchanged. 

   Temperatures across the Portland Metro into the Columbia Gorge have
   warmed into the mid 60s to 70s under mostly sunny skies. Surface
   objective analysis and observed 18z soundings from MFR and OTX
   continue to indicate MLCIN in place across much of the region from
   the Cascades/Colombia Gorge westward. The surface front and main
   upper-level forcing remain offshore and are expected to move
   eastward across the region by the late afternoon/early evening.
   Forecast soundings continue to indicate weakening of MLCIN along
   with steepening low to mid-level lapse rates as cooling aloft with
   the trough modifies profiles. This should allow for thunderstorm
   development through the afternoon/evening, with potential for
   supercells capable of large hail, damaging wind, and possibly a
   tornado or two.

   See previous discussion below for more information.

   ..Thornton/Smith.. 03/26/2025

   .PREV DISCUSSION... /ISSUED 1130 AM CDT Wed Mar 26 2025/

   ...Pacific Northwest...
   Satellite imagery this morning shows an upper low approaching the
   coast with mostly sunny skies over much of the region.  A 100 kt
   500-mb speed max will rotate through the base of the trough and
   overspread coastal OR/WA by mid evening as the upper low shifts
   east.  An associated cold front should arc from off the Washington
   Coast to southward along the Oregon Coast by evening.

   Cold-air advection in the mid levels and diurnal heating will
   contribute to steepening lapse rates, and the development of weak to
   locally moderate buoyancy (250-1500 J/kg SBCAPE) by mid-late
   afternoon.  Strengthening large-scale forcing for ascent and
   negligible CINH will favor isolated thunderstorms developing by
   mid-late afternoon and increasing in coverage through the early
   evening.  Forecast hodographs indicate supercells are likely with
   the stronger, more persistent updrafts.  Large hail (1-2 inches in
   diameter) will be possible.  The elongated and perhaps locally
   augmented hodograph in the vicinity of terrain favored areas (i.e.,
   near the Columbia River with a modest easterly component) may enable
   a short-duration tornado risk.  Severe gusts are also possible with
   the stronger cores and outflow surges as convection matures during
   the evening and gradually diminishing late.

   ...Texas Lower Rio Grande River Valley...
   A weak disturbance will approach the Rio Grande through mid
   afternoon with a cirrus shield expected to persist through peak
   heating.  A moist boundary layer sampled by morning area raobs and
   some filtered heating will promote widely scattered to scattered
   storms developing this afternoon.  Relatively weaker flow in the low
   to mid levels will limit overall storm organization, but transient
   supercell/multicells are possible.  The stronger storms may be
   capable of a localized hail/wind threat.

   ...Southwest IA...
   A strengthening warm-air advection regime overnight from KS into
   MO/IA will likely lead to the development of widely scattered
   showers/thunderstorms in the vicinity of a warm front.  Forecast
   soundings show elevated instability (1000 J/kg MUCAPE) developing as
   the profile moistens near 850 mb.  A stronger storm capable of small
   to marginally severe hail cannot be ruled out, but the threat
   appears too limited to introduce low-severe probabilities.

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