000
acus01 kwns 260549
swody1
Storm Prediction Center ac 260547
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
1247 am CDT sun may 26 2013
Valid 261200z - 271200z
..there is a slight risk of severe thunderstorms across a large part of the
southern...central and northern High Plains...
...
Synoptic pattern will undergo little change with a low amplitude
Omega blocking regime forecast to persist through Sunday. Several
vorticity maxima will move through western U.S. Upper low circulation
and into the central and northern High Plains. At the surface a Lee low will
persist over eastern Colorado with a dryline extending southward through the central
and southern High Plains. Quasi-stationary west-northwest-east-southeast oriented front should
extend from the middle MS valley nwwd through Nebraska into Wyoming.
..nrn through Central Plains...
Persistent broad fetch of southerly-south-southeasterly winds east of Lee trough will
contribute to further moistening of the boundary layer with middle to
upper 60s dewpoints likely over portions of the Central Plains and
upper 50s to near 60 over the northern plains. Meanwhile...west-southwesterly flow
aloft will maintain feed of steep lapse rate above the moist axis.
The atmosphere should become moderately unstable Sunday afternoon
with an axis of 2000-3000 j/kg MLCAPE from eastern Montana and western South Dakota southward
into western/central Nebraska. Storms should once again develop over the higher
terrain and intensify as they move east-northeastward into the axis of stronger
instability. Other storms may initiate farther south along dryline
across eastern Colorado/western Kansas. Much of this region will exist on southeastern
periphery of upper low circulation with 25-35 knots 500 mb flow above
southeasterly near surface winds supporting 30-40 knots effective shear. Supercell
modes will be likely with initial storms that develop with primary
threat being very large hail. Isolated tornadoes may also be
possible. Eventually storms may evolve into one or more
clusters...and additional storms may also develop during the evening
across Nebraska on nose of strengthening low level jet.
..srn High Plains...
Isolated to widely scattered storms may develop within zone of
deeper mixing along dryline across the southern High Plains. Storms will
intensify as they move into moist axis with 2000-3000 j/kg MLCAPE.
Vertical shear will be weaker than farther north...but 25-35 knots
effective shear will support multicells and also some supercell
structures with large hail and damaging wind gusts the main threats
through middle evening.
.Dial/Dean.. 05/26/2013
Mesoscale Discussion
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acus11 kwns 260824
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 260824
sdz000-261000-
Mesoscale discussion 0804
National Weather Service Storm Prediction Center Norman OK
0324 am CDT sun may 26 2013
Areas affected...north central and ecntrl South Dakota
Concerning...Severe Thunderstorm Watch 221...
Valid 260824z - 261000z
The severe weather threat for Severe Thunderstorm Watch 221
continues.
Summary...an isolated severe threat should continue early this
morning across north central South Dakota with the threat developing southeastward into ecntrl
South Dakota over the next few hours. Large hail and isolated wind damage will
be primary threats.
Discussion...a cluster of strong to severe thunderstorms is
currently ongoing just to the southwest of Mobridge South Dakota located along
the northern edge of moderate instability. In north central South Dakota...objective
analysis estimates that MUCAPE values are near 2000 j/kg with the
instability axis extending east-southeastward to near Sioux Falls. This suggests
the storms will continue to move southeastward to areas north of Pierre and
to the west of Sioux Falls near daybreak. Regional WSR-88D vwps show
unidirectional winds above the inversion with sufficient speed shear
for storm organization. This along with the instability should
continue a severe threat early this morning. Steep lapse rates
should be favorable for large hail with the more intense cores.
Bowing line segments could also be associated with isolated wind
damage.
.Broyles/corfidi.. 05/26/2013
..please see www.Spc.NOAA.Gov for graphic product...
Attention...WFO...fsd...abr...unr...
Latitude...Lon 43399886 44350149 44630219 45310225 45660187 45820106
45229905 44299814 43399886
