Convective Outlook

U.S. Severe Weather Forecast

000 
acus01 kwns 201219 
swody1 
Storm Prediction Center ac 201217 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0717 am CDT Monday may 20 2013 


Valid 201300z - 211200z 


..there is a MDT risk of severe thunderstorms this afternoon and tonight over 
parts of North Texas...central and eastern OK...northwest Arkansas...extreme 
southeast Kansas...and southern MO.... 


..there is a slight risk of severe thunderstorms from central Texas into much of 
the upper MS valley and Great Lakes region.... 


... 
Morning water vapor loops show a broad upper trough over the western 
and central states...with a progressive shortwave trough tracking 
eastward across northern nm. This feature will move into the 
Southern Plains by early afternoon...helping to initiate another 
round of strong to severe thunderstorms over the Southern Plains. 


A surface cold front currently extends roughly from lts-bvo. This 
front is likely to move slightly southeastward today and will 
provide the focus for afternoon thunderstorm development. Various 
mesoscale models differ on timing of strong/severe storms...but 
agree on storms forming over central OK by about 20z and building 
quickly northeastward into southeast Kansas and western MO. The initial 
storms will likely be supercelluar with very large hail...damaging 
winds...and tornadoes possible. Those storms that form over 
southern OK into North Texas appear to have the greatest chance of 
remaining discrete and posing a risk of significant severe weather 
for several hours into the evening. Meanwhile...storms that form 
from central OK northeastward into southeast Kansas and MO appear likely 
to organize into broken lines and clusters by early evening capable 
of widespread damaging winds...large hail...and a few tornadoes. 
Similar to yesterday...middle level lapse rates of 7.5-8.0 c/km...very 
large cape...and favorable shear values will pose a risk of isolated 
strong tornadoes across portions of the moderate risk area. 


..upper MS valley and western Great Lakes... 
Early visible satellite imagery shows only broken cloud cover over 
parts of Iowa/WI eastward into mi/OH. Relatively strong daytime 
heating and little cap should result in scattered thunderstorms 
today and tonight to the east of a surface low over Minnesota. MLCAPE 
values of 1500-2000 j/kg will promote vigorous updrafts in this 
region...while sufficiently strong vertical shear helps to organize 
the convection. Present indications are that multiple 
lines/clusters of thunderstorms will affect this region...with a few 
supercells possible. Hail and damaging winds are the main 
threats...but isolated tornadoes cannot be ruled out. 


... 
South of the moderate risk area in Texas...confidence is a little 
higher today compared to last few days that isolated storms will 
form along the dryline. Any storm that can form in this area will 
pose a risk of very large hail and damaging winds for a few hours 
this evening. 


.Hart/leitman.. 05/20/2013 

Mesoscale Discussion

000 
acus11 kwns 201346 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 201346 
moz000-ksz000-201445- 


Mesoscale discussion 0724 
National Weather Service Storm Prediction Center Norman OK 
0846 am CDT Monday may 20 2013 


Areas affected...southeastern Kansas...W-cntrl MO 


Concerning...severe potential...watch possible 


Valid 201346z - 201445z 


Probability of watch issuance...40 percent 


Summary...a narrow corridor of thunderstorms has formed within the past hour 
across parts of southeastern Kansas and into west-central MO. This activity should 
pose a primary risk for large hail...and a lesser threat for strong 
to potentially severe wind gusts. It is uncertain whether thunderstorms will be 
sustained for long enough to require a ww...but trends will continue 
to be monitored. 


Discussion...visible satellite imagery shows a corridor of 
intensifying convection developing within an elevated baroclinic 
zone and ahead of an approaching upper impulse over S-central Kansas...in 
the wake of overnight convection which has moved into central MO and 
has weakened. Regional soundings /E.G. Sgf and top/ suggest this 
activity is likely rooted above the boundary layer...and located 
along the periphery of a plume of steep midlevel lapse 
rates...posing a primary risk for large hail. There is some 
uncertainty whether convection will be sustained for more than 1-2 
hours with northeastward progression into west-central MO...where convection 
overnight may have stabilized the air mass somewhat. 
However...should trends indicate convection will maintain current 
intensity or strengthen...and show signs of becoming rooted within 
the boundary layer...then a ww may need to be considered. 


.Rogers/Kerr.. 05/20/2013 


..please see www.Spc.NOAA.Gov for graphic product... 


Attention...WFO...sgf...eax...top...ict... 


Latitude...Lon 38359312 37809417 37429535 37449591 37579620 37929622 
38419550 38869480 39099426 39149368 39089330 38779300 
38359312