SPC AC 260600

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CDT Tue May 26 2026

   Valid 261200Z - 271200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   WEST AND SOUTHWEST TEXAS...

   ...SUMMARY...
   Thunderstorms with large hail, severe wind gusts and a couple
   tornadoes are expected this afternoon and evening across parts of
   west and southwest Texas. Isolated severe gusts and a marginal
   tornado threat will be possible in parts of Kentucky. Isolated
   severe gusts and hail may also occur in parts of the Upper Midwest
   and northern Rockies.

   ...West and Southwest Texas...
   A mid-level shortwave trough will move eastward today across far
   west Texas. At the surface, a low will deepen near Big Bend as an
   axis of low-level moisture sharpens from the Rio Grande Valley
   northward into west Texas. Along this axis, surface dewpoints will
   be in the upper 60s and lower 70s F, which will contribute to
   moderate instability by afternoon. Near the moist axis, a
   north-to-south corridor of low-level convergence is forecast, along
   which thunderstorm development is expected by late morning. Storm
   coverage is forecast to expand and move eastward from west Texas
   into southwest Texas this afternoon.

   Along the instability axis, MLCAPE is forecast to peak in the 2000
   to 3000 J/kg range during the mid to late afternoon. RAP forecast
   soundings near the instability axis at 21Z have 0-6 km shear in the
   30 to 40 knot range with 700-500 mb lapse rates around 7.5 C/km.
   This will be favorable for supercells with large hail. Hailstones
   greater than 2 inches in diameter will be possible with the more
   intense storms. In addition, forecast hodographs are curved and 0-3
   km storm-relative helicity is forecast to increase to above 200
   m2/s2, which will support a tornado threat. Cells are expected to
   merge into a line during the late afternoon, potentially increasing
   the threat for severe gusts. This line is forecast to move across
   southwest Texas during the early evening.

   ...Kentucky...
   South-southwesterly mid-level flow will be in place over the Ohio
   and Tennessee Valleys today. At the surface, a mesolow is forecast
   to develop over far western Kentucky this afternoon. To the east of
   the low, moisture advection will increase surface dewpoints to near
   70 F across much of Kentucky, where MLCAPE is forecast to peak
   around 1000 J/kg. Within this unstable airmass, low-level flow over
   southern and central Kentucky will be backed to the south-southeast.
   This, combined with increasing low-level flow, will create curved
   hodographs. Forecast soundings at 21Z south of Lexington have 0-3 km
   storm-relative helicity increasing to 150 m2/s2 by mid afternoon,
   which should support a marginal tornado threat. Isolated severe wind
   gusts will also be possible.

   ...Upper Midwest...
   Mid-level flow will be westerly today across much of the Upper
   Midwest. At the surface, a quasi-stationary frontal boundary will be
   in place from eastern North Dakota to northern Wisconsin. South of
   this front, surface dewpoints in the 60s F will contribute to
   pockets of moderate instability by afternoon. Scattered
   thunderstorms will develop across this unstable airmass and move
   east-southeastward during the afternoon. MLCAPE in some areas are
   forecast to peak in the 1500 to 2500 J/kg range, with low-level
   lapse rates becoming steep. This will be sufficient for isolated
   severe gusts. Hail will also be possible, mainly from southeast
   Minnesota into Wisconsin, where some models suggest instability will
   be stronger.

   ...Northern Rockies...
   A mid-level low will move southward across northern California
   today. To the northwest of the low across the northern U.S., flow
   will be from the south-southeast. At the surface, a low will deepen
   across western Montana with upslope easterly flow located over much
   of western Montana. As surface heating takes place today, an axis of
   instability is forecast from northwest Montana extending
   southeastward into far northwest Wyoming. Scattered thunderstorms
   will develop in the higher terrain and move northward along and near
   this axis of instability. Low-level lapse rates will be very steep,
   which will contribute to a potential for severe wind gusts. Hail
   will also be possible, mainly over western Montana where instability
   is forecast to be the strongest.

   ..Broyles/Chalmers.. 05/26/2026

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