SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1151 PM CST Sat Jan 23 2021

Valid 241200Z - 251200Z


A few severe thunderstorms capable of producing large hail and
isolated wind damage will be possible this afternoon through tonight
across parts of the southern Plains.

...Southern Plains/Ozarks...
An upper-level trough will move eastward across the Desert Southwest
today as southwest mid-level flow becomes established in the
southern Plains. At the surface, a cold front will advance
southeastward across the southern Plains today as moisture advection
occurs to the south of the front. By afternoon, the front position
should be located from near Lubbock northeastward into southern
Oklahoma. Surface dewpoints to the south of the front in the Red
River Valley and across northwest Texas are forecast to be mostly in
the 50s F. A capping inversion should prevent convection from
initiating for much of the day. But as surface heating and low-level
convergence increase, isolated thunderstorms appear likely to
develop in north Texas along and just ahead of the front during the
late afternoon. Convection is forecast to expand rapidly in the
early evening as warm advection increases across north Texas and
southern Oklahoma. Thunderstorm development should continue across
much of Oklahoma, north Texas and Arkansas as the upper-level trough
approaches during the overnight period.

Instability is forecast to gradually increase today to the south of
the front across central and north Texas. By early evening, a pocket
of moderate instability may develop across parts of west-central
Texas. As instability increases during the evening, a severe threat
will be possible in southern Oklahoma and north Texas. NAM forecast
soundings to the west of the Dallas/Fort Worth Metro during the
early evening have MLCAPE reaching 1000 J/kg. Effective shear is
forecast to gradually increase from around 55 kt at 00Z to 70 kt at
06Z. As a result, the severe threat is forecast to gradually
increase during the evening. Forecast soundings suggest that the
steepest lapse rates will be located above 700 mb. This will be
favorable for hail, especially with supercells that can organize.
Isolated strong wind gusts may also occur in southern Oklahoma and
north Texas as cells become more surface-based during the evening.
Thunderstorms, accompanied by an isolated severe threat, are
forecast to move eastward across southeast Oklahoma and northeast
Texas in the mid to late evening. A marginal severe threat may also
develop in parts of Arkansas during the overnight period as warm
advection increases.

..Broyles/Lyons.. 01/24/2021

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