- Day Three
acus02 kwns 190446
Storm Prediction Center ac 190445
Day 2 convective outlook
National Weather Service Storm Prediction Center Norman OK
1145 PM CDT Friday Apr 18 2014
Valid 201200z - 211200z
..there is a slight risk of severe thunderstorms across West Texas...
isolated severe thunderstorms are expected to develop along a
dryline across the southern High Plains of West Texas. A few strong
storms may also develop across portions of western Oklahoma into
Slow-moving upper low is drifting eastward across the lower Colorado River
valley. This feature is expected to gradually deamplify and eject
into the southern rockies early Sunday morning with the trough axis
likely extending across the southern High Plains of West Texas by 21/00z.
Strongest belt of middle-high level flow will translate over northern Mexico
with 30-40kt at 500mb forecast to extend over West Texas dryline by
peak heating. Deep-layer shear should increase enough to support
sustained rotating updrafts...especially south of I-20 where surface-6km
values should exceed 40kt.
Latest model guidance continues to suggest 50s surface dew points will
advance nwwd into convergent Lee trough/dryline such that ample
instability should exist by early-middle afternoon for robust updrafts.
In fact...cooling profiles aloft may allow inhibition to weaken
enough for thunderstorm initiation fairly early...possibly by 18z.
However...continued boundary layer heating could result in SBCAPE
values approaching 1500 j/kg within strongly sheared environment.
Forecast sounding at maf at 21/00z strongly supports supercell
development. Convection that evolves across the southern High Plains
should move east-southeastward though northeastward development along the dryline is
expected across OK into Kansas. Thunderstorms that develop across the Central
Plains will do so within considerably weaker shear and forecast
instability does not appears strong enough to warrant more than 5
percent severe probs despite scattered coverage expected.
Large hail is the primary severe threat with supercells along with
gusty winds. While a brief tornado can not be ruled out over West
Texas low level shear may be inadequate to support more significant