U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 220441 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1141 PM CDT sun Apr 21 2019 


Valid 221200z - 231200z 


..there is a slight risk of severe thunderstorms from southeast nm 
across northwest Texas and into far southwest OK... 


... 
Scattered severe thunderstorms capable of mainly hail and damaging 
winds are possible from southeast New Mexico across the South Plains 
and into parts of northwest Texas and southwest Oklahoma from late 
afternoon Monday through evening. Isolated strong to severe storms 
are also possible across parts of southern Wisconsin, eastern Iowa, 
and northern Illinois. A weak, brief tornado cannot be ruled out in 
either area. 


... 
An upper low will drop south from Arizona into northwest Mexico with a 
leading shortwave disturbance moving out of northern Mexico across 
West Texas. At the surface, a stalling front will stretch roughly from 
southeast nm into central OK by 00z, with winds veering to easterly 
across the High Plains. Mid to upper level southwesterly winds will 
increase to an average of 40-70 kt respectively, enhancing the 
potential for scattered severe storms. 


To the north, a shortwave trough will move into the upper MS valley 
during the afternoon, with a surface low moving from Iowa into Michigan. 
Southerly winds will increase ahead of this low, enhancing low-level 
shear, with the low track becoming a favorable corridor for isolated 
severe storms. 


..southeast nm...South Plains...southwest OK... 
scattered storms are expected to form around 21z from central and 
southeast nm into parts of west TX, where heating is strongest south 
of the front. Hail is possible with the nm cells, as well as into 
the South Plains. A brief tornado cannot be ruled out near peak 
heating, near the boundary, and before cells grow upscale into a 
possible mesoscale convective system. The greatest potential for damaging winds will likely 
be along the boundary, extending into northwest TX, as storms move 
along it, aided by strong east/northeast surface winds just north of 
the boundary. A few storms may remain strong to severe into far 
southwest OK, before the air mass overturns with more widespread 
precipitation. 


..eastern Iowa...Northern Illinois...southern WI... 
upstream heating of a 50s dewpoint air mass and increasing southerly 
winds ahead of the surface low will result in an axis of around 1000 
j/kg MLCAPE by afternoon across IA/IL/WI. Forecast soundings show 
some capping around 700 mb, but lift near the low track is expected 
to support thunderstorm development, which will be centered over the 
tri-state area. While winds in the mid and upper levels will not be 
particularly strong (short hodographs), low-level veering of the 
winds with height may support rotating storms with marginal hail, 
wind, or a brief tornado (especially over WI where LCLs will be 
lower). 


.Jewell/karstens.. 04/22/2019 


$$ 

Mesoscale Discussion


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Storm Prediction Center mesoscale discussion 220015 
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Mesoscale discussion 0418 
National Weather Service Storm Prediction Center Norman OK 
0715 PM CDT sun Apr 21 2019 


Areas affected...parts of north central Kansas 


Concerning...severe potential...watch unlikely 


Valid 220015z - 220145z 


Probability of watch issuance...5 percent 


Summary...thunderstorm activity capable of producing small hail and 
a few strong wind gusts may persist, and possibly increase some, for 
a period this evening. However, overall, the threat still appears 
marginal enough that a severe weather watch will not be needed. 


Discussion...ongoing small, but sustained cluster of thunderstorms 
has accelerated some while advancing east-northeastward during the 
past couple of hours, from near 20 to around 30 kt. Activity has 
been mostly Post-cold frontal, aided by mid-level cooling and 
sufficient boundary layer moisture to contribute to cape locally up 
to around 1000-1500 j/kg. Deep layer wind fields and shear are 
mostly modest to weak, but initially steep lower/mid tropospheric 
lapse rates have been sufficient to support mainly small hail and a 
few strong wind gusts. 


It remains unclear how much longer this activity will maintain 
strength as it spreads near/to the south and east of Hill City. It 
seems possible that it may weaken as the cold front overtakes the 
dryline and supports the initiation of new thunderstorm activity 
downstream, around the Hays, Russell, Smith Center and Beloit 
vicinities. It is possible that shear associated with strengthening 
southerly 850 mb flow across this region could aid organization of 
consolidating new development. But any associated severe wind 
threat probably will be limited by the onset of boundary layer 
cooling, which likely will result in an increasingly marginal 
thermodynamic environment for vigorous convection. 


.Kerr/Hart.. 04/22/2019 


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


Attention...WFO...top...ict...Gid...ddc...gld... 


Latitude...Lon 39949884 40019749 39509668 38279797 38069948 38480001 
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