SPC AC 210502
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1202 AM CDT Sat Apr 21 2018
Valid 211200Z - 221200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM A PORTION
OF NORTH CENTRAL THROUGH EAST TEXAS INTO WESTERN LOUISIANA...
A few strong to severe thunderstorms are possible across a portion
of Texas later today and southwest Louisiana tonight.
Upper low situated over the southern Rockies will continue through
the central and southern Plains today and lower MS Valley tonight.
Warm front now over the northern Gulf to deep South TX will advance
northward into central TX through southwest LA, while a cold front
advances southeast, reaching the TX coast by the end of the period.
...Texas through western Louisiana...
Several vorticity maxima will rotate through the upper low
circulation as it advances east during the period. However, the
deeper forcing for ascent accompanying these features will remain
north of warm sector. A large area of warm-advection rain with
embedded thunderstorms should be ongoing from a portion of north
central TX into OK, and this activity will expand east during the
day. Farther south, destabilization will occur primarily in response
to theta-e advection as the warm front advances northward toward
central TX. A secondary area of weak destabilization might occur
farther west across northwest through west central TX in wake of
early convection where some boundary layer warming is possible in
advance of southeast-advancing cold front. MUCAPE in all of these
areas is expected to remain near or below 500 J/kg. Thunderstorms
may undergo some intensification this afternoon within corridor of
destabilization across central TX where the low-level jet intersects
the warm front. While vertical wind profiles with 40-50 kt effective
bulk shear would support a conditional risk for some supercell
structures, tendency will be for storms to move toward cool side of
boundary after initiation. Additional storms may develop this
afternoon near the triple point over northwest through west central
TX as boundary layer destabilizes and a vorticity maxima rotates
through base of the upper trough enhancing deeper forcing for
ascent. This activity might pose a risk for marginally severe hail
and gusty winds. Tendency may be for storms to evolve into
quasi-linear structures over east TX as cold front advances east
during the evening and overnight, posing some risk for mainly a few
strong wind gusts. Primary limiting factor for a more robust severe
threat is expected to be a marginal thermodynamic environment.
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z