- Day Three
acus03 kwns 240713
Storm Prediction Center ac 240712
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
0212 am CDT Thursday Apr 24 2014
Valid 261200z - 271200z
..there is a slight risk of severe thunderstorms across the central and Southern
Scattered severe thunderstorms are expected to develop along a
dryline across portions of Kansas...Oklahoma...and parts of West
Texas. Very large hail...and possibly tornadoes...can be expected.
..central and Southern Plains...
Strong middle-level speed maximum is forecast to round the base of a
progressive trough along the southwestern U.S./Mexican border early Saturday
before shifting into nm by 27/00z. This feature will then eject
into the Central High plains of western Kansas overnight...increasing to
80kt+ at 500mb. Intense 12-hour middle-level height falls...approaching
200m...will develop across the High Plains centered on southeastern Colorado.
As upper trough shifts into the southern rockies...surface low will deepen
over eastern Colorado and a well-defined Lee trough will extend southward into northern
Mexico. Intense heating is expected along this trough during the
day and a dryline should mix into the eastern Texas Panhandle by 21z.
While warm sector boundary layer moisture is expected to gradually
increase across the southern/Central Plains over the next few days it
appears dryline convection may initially ingest 50s surface dew points
as temperatures rise through the 80s...to perhaps near 90f farther
south across the Edwards Plateau. Convective temperatures should be
breached by 21z and scattered supercells are expected to develop along the
boundary. This activity will initially be driven by diabatic
heating as large-scale forcing associated with approaching speed maximum
will lag this corridor of initiation until well after dark. Delayed
large-scale support may limit the number of storms that ultimately
evolve along the dryline.
Convection that develops during the late afternoon will do so along
a narrow corridor of 3000 j/kg SBCAPE and should mature into the
early evening hours as vertical shear increases from the west.
Supercells with very large hail...greater than 2 inches...are
expected. As thunderstorms shift east and boundary layer cools slightly
there may be a propensity for cloud bases to lower and take
advantage of lower 60s surface dew points. As a result...tornado threat
should increase during the early evening hours before activity
decouples from the boundary layer.
With large scale forcing expected to eject into the plains overnight
there may be convective redevelopment along the dryline as it begins
to surge across southwestern Kansas/western OK/northwestern Texas.
Severe probabilities may be increased across this region if
middle-level speed maximum/forcing overspreads the dryline at a more
favorable time diurnally.