acus03 kwns 190732
Storm Prediction Center ac 190730
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
0230 am CDT sun may 19 2013
Valid 211200z - 221200z
..there is a slight risk of severe thunderstorms from the upper Great Lakes
region southwestward into central Texas...
Slight weakening/deamplification of the lingering middle- and
upper-level storm system over the central U.S. Is forecast this
period...as a digging/strengthening trough/low shifts south-southeastward into the
western/northwestern U.S. Through the end of the period. The central U.S.
System will remain the primary driver for the majority of the
convective potential this forecast.
..upper Great Lakes region southwestward into central Texas...
Model differences with respect to timing of a short-wave trough
rounding the southern periphery of the upper low and widespread
convective activity during intervening days is yielding fairly
substantial uncertainty with respect to details of the day 3
/Tuesday/ severe weather potential stretching from the Great Lakes
At this time...it appears that a cold front -- moving across the central and
Southern Plains at the start of the period -- should begin to wash out as
eastward progression slows into the afternoon. While clouds and ongoing
showers and thunderstorms ahead of the front will likely inhibit
heating/destabilization in some areas into the
afternoon...substantial destabilization is forecast by late
afternoon -- particularly from the southeastern OK/western Arkansas vicinity southwestward into
central Texas ahead of the dryline.
Boundary-layer capping should limit development into the
afternoon...but storm development is eventually expected -- with
coverage depending to some degree upon timing of a short wave trough
crossing the southern rockies day 2 and then shifting into Texas day 3.
With ample shear and likely-to-be strong instability across the
arklatex and into central Texas...significant severe weather --
primarily very large hail -- will be possible. However...with
questions regarding convective coverage/concentration...will
introduce only 15% severe probability at this time.
Farther north -- across MO and as far northeastward as the upper Great Lakes
region...the scenario is even more unclear...as more widespread
storms ongoing early in the period will likely persist through the
day. Therefore...more uncertain degree of destabilization -- as
well as generally weaker shear due to more meridional/unidirectional
flow aloft -- should limit threat to some degree. Still...locally
severe storms capable of producing hail and damaging winds and
possibly an isolated tornado can be expected. Threat should
diminish overnight...though storms/limited potential for severe
weather will continue through the end of the period.