acus02 kwns 190602
Storm Prediction Center ac 190600
Day 2 convective outlook
National Weather Service Storm Prediction Center Norman OK
0100 am CDT sun may 19 2013
Valid 201200z - 211200z
..there is a MDT risk of severe thunderstorms from parts of southeastern Kansas/west central
and southwestern MO southwestward into central OK...
..there is a slight risk of severe thunderstorms from the upper MS valley/upper
Great Lakes region south-southwestward into north central Texas...
A large upper low is forecast to linger in place across the South Dakota/Nebraska
vicinity...while a middle-level jet streak around the southern fringe of the
low ejects from the southern rockies into the central U.S. During the
period. While a second low/trough is forecast to approach the Pacific
northwest coast late...the central U.S. Storm system will be the system of
interest with respect to severe potential on Monday.
At the surface...a low is forecast to remain over the South Dakota vicinity
beneath the upper low...with a trailing cold front forecast to shift
eastward across the plains. As the aforementioned jet streak shifts into
the S central portion of the country...secondary cyclogenesis is
forecast to occur along the front in the southwestern OK vicinity...near the
intersection of the front and a developing dryline. The cold front
and dryline should serve as primary foci for afternoon development
of widespread/severe storms.
..upper MS valley/upper Great Lakes southwestward into the Southern Plains...
While details remain difficult to discern due to multiple rounds of
widespread/intervening convection...another substantial severe
weather event is forecast Monday/day 2 across the central Continental U.S..
Weakening/diminishing convection may be ongoing ahead of the front
across the warm sector...but as storms/cloudiness wane through the
morning in most areas...expect the onset of heating to drive strong
airmass destabilization. By late afternoon...the
pre-frontal/pre-dryline warm sector should feature 2500 to 3500 j/kg
mixed-layer cape. As large-scale ascent -- aided by the approaching
jet streak and focused along low-level boundaries --
increases...expect development/rapid growth of initial convection
during the middle afternoon hours. As shear increases in conjunction
with intensifying flow aloft...storms should rapidly acquire
rotation -- particularly where cape/shear juxtaposition appears most
favorable across the MDT risk area. Here...threat for very large
hail and tornadoes will exist. Threat for damaging winds will
increase into the evening...as storms evolve into linear clusters in
some areas. Even so...rotating/supercell storms should linger
locally well into the evening hours -- with continued tornado and
large hail potential. Threat should finally begin to diminish
overnight...as the airmass slowly cools/stabilizes -- particularly
across northern portions of the risk area.