000
acus02 kwns 251701
swody2
Storm Prediction Center ac 251659
Day 2 convective outlook
National Weather Service Storm Prediction Center Norman OK
1159 am CDT Sat may 25 2013
Valid 261200z - 271200z
..there is a slight risk of severe thunderstorms across the northern and Central
Plains...
...
Weak height falls are expected to spread into the northern High Plains
late in the period as a weak short-wave trough ejects across the northern
rockies to a position from western Montana into northwestern Wyoming at 27/12z. This
feature will undoubtedly enhance the westward movement of boundary layer
moisture across the northern High Plains toward scntrl Montana as Ely low
level component...at least 1km deep...forces lower 50s surface dew
points toward bil. While large scale ascent with short-wave will
lag peak heating...it appears convection should evolve off the northern
Absaroka Range...and northern Big Horn Mountains. This activity should
then evolve and spread toward southeastern Montana/extreme northestern Wyoming where shear
profiles will favor supercells. Large hail and isolated tornadoes
can be expected with this activity. If sufficient instability
develops across this region there is concern for very large hail and
possibly a strong tornado. 23z forecast sounding at 4bq supports
this possibility as it depicts a very favorable profile for strong
rotating updrafts with SBCAPE in excess of 2500 j/kg.
Farther south across the Central Plains...it/S not particularly clear
if a disturbance will eject across Colorado during the afternoon hours but
forecast height fields are suppressed somewhat across this region
into the evening hours suggesting the possibility.
Additionally...low level jet is expected to increase markedly across Kansas by
27/00z which suggests a weak feature may be flattening the ridge
across this region. With backing flow expected across Nebraska it
appears east-west surface boundary should establish itself just north of I-70
and this will prove favorable for robust convective development
during the late afternoon/evening hours...especially as low level jet impinges
on the boundary. Strong heating across western Kansas will likely
contribute to initial thunderstorm development and deep layer shear seems
adequate for maintenance of slow moving supercells and
strong/organized multi-cell clusters.
Roughly 20kt of 500mb flow will also extend southward along the dryline
across West Texas. It appears diurnal heating will break the cap
across this region where SBCAPE should be at or above 3000 j/kg. At this
time will maintain 5 percent severe probs for hail/wind along the
southern dryline but there is concern probabilities may need to be
increased to account for scattered organized multi-cell clusters.
.Darrow.. 05/25/2013
