000
acus01 kwns 211141
swody1
Storm Prediction Center ac 211139
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0639 am CDT Tuesday may 21 2013
Valid 211300z - 221200z
..there is a MDT risk of severe thunderstorms over parts of central and East
Texas...southeast OK...northwest la...and western Arkansas...
..there is a slight risk of severe thunderstorms from the Southern Plains into
the middle MS valley and Great Lakes states...
...
Morning water vapor imagery shows a well-defined upper trough over
the nm/Texas border. This feature is forecast to track eastward into
the Southern Plains today...setting the stage for another active day
of severe thunderstorms.
Scattered strong thunderstorms are ongoing this morning across
southern OK...in a region of low level warm advection and ahead of a
surface cold front. These storms appear likely to increase in
coverage through the morning...spreading southeastward into North Texas
and western Arkansas. Ample low level moisture and moderate cape values
will pose a risk of large hail and locally damaging winds.
By early afternoon...strong heating south of the storms will promote
further intensification across much of north central and northeast
Texas. Steep middle level lapse rates and dewpoints near 70f will yield
MLCAPE values of 2000+ j/kg. As the upper trough
approaches...strengthening vertical shear suggests a risk of
discrete supercells capable of very large hail and tornadoes.
The activity is forecast to congeal into lines/clusters of storms by
early evening spreading rapidly eastward into AR/la. These storms
will likely have an enhanced risk of widespread damaging winds.
..MO/Illinois northward into lower Michigan...
Multiple bands of thunderstorms have affected the middle MS valley
overnight. These storms have weakened instability and are providing
uncertainty regarding the coverage/intensity of thunderstorms later
today. Have maintained the slight risk area...but have generally
decreased probabilities in these regions. The area that appears
most likely to see isolated severe storms later today would be
across lower Michigan as a shortwave trough now over MO/Illinois rotates
northeastward.
.Hart/leitman.. 05/21/2013
Mesoscale Discussion
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acus11 kwns 210921
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 210920
arz000-okz000-211015-
Mesoscale discussion 0745
National Weather Service Storm Prediction Center Norman OK
0420 am CDT Tuesday may 21 2013
Areas affected...part of southern/eastern OK into west central Arkansas
Concerning...Severe Thunderstorm Watch 199...
Valid 210920z - 211015z
The severe weather threat for Severe Thunderstorm Watch 199
continues.
Summary...an isolated hail threat continues across ww 199 into the
early morning...as new storms develop from Kiowa County OK through
central McClain/southern Cleveland counties to McIntosh County OK.
Discussion...a broad warm air advection zone extending into southern OK within the nose
of a 45-50 knots south-southwesterly low level jet combined with a northward influx of moderate
instability suggests thunderstorm development will continue from west-east across
ww 199. Effective bulk shear up to 50 knots supports storm
organization. These factors combined with steep midlevel lapse
rates of 7.5-8 c/km per objective analyses will favor a continued
potential for additional stronger storms to produce primarily a hail
threat.
Since 0840z...regional radar imagery indicated an increase in thunderstorm
development from central McClain County OK to central and eastern Kiowa
County OK. These storms appear to be forming along a cold front
advancing southward into central and southwestern OK where the inflow of moderate
instability is supporting this new development.
.Peters.. 05/21/2013
..please see www.Spc.NOAA.Gov for graphic product...
Attention...WFO...lzk...shv...tsa...oun...
Latitude...Lon 34109762 34319816 34829893 35009855 35159766 35369712
35369628 35869562 35769372 35299379 34669450 34539455
34119526 34049714 34109762
