Convective Outlook

U.S. Severe Weather Forecast

000 
acus01 kwns 161952 
swody1 
Storm Prediction Center ac 161950 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0250 PM CDT Thu Aug 16 2018 


Valid 162000z - 171200z 


..there is a slight risk of severe thunderstorms across parts of 
Oklahoma...eastern Kansas...western Missouri...and far northwestern 
Arkansas... 


... 
The greatest concentration of severe-storm potential appears to be 
this afternoon and evening over portions of central/eastern 
Oklahoma, eastern Kansas and western Missouri. 


..20z update... 
A well-defined mesoscale convective vortex over western/central OK is noted on radar and 
visible satellite imagery as of 1950z. This mesoscale convective vortex will continue moving 
east-northeastward with time, and the better severe hail/wind 
potential will likely remain along and to the east of this low-level 
circulation. Have therefore adjusted the slight risk eastward across 
western/central OK. The slight risk has also been expanded slightly 
northward across northeastern Kansas and northwestern MO where a weak 
front/boundary will likely focus additional convective development 
and an isolated large hail/damaging wind risk this afternoon. For 
more information on the short-term severe potential across parts of 
central/eastern OK and eastern KS, see mesoscale discussion 1301. 


.Gleason.. 08/16/2018 


Previous discussion... /issued 1122 am CDT Thu Aug 16 2018/ 


..Central Plains... 
Morning satellite imagery shows a well-defined mesoscale convective vortex moving eastward 
into western OK. Strong heating is occurring ahead of this feature 
across much of OK and eastern KS, where dewpoints in the 70s and 
steep mid level lapse rates will yield afternoon MLCAPE values of 
2000-3000 j/kg and little cin. Model guidance is consistent in the 
development of scattered thunderstorms by mid afternoon throughout 
this area. A potent shortwave trough over NE is also digging 
southeastward toward the region, resulting in strengthening 
mid/upper level wind fields. This will promote increased convective 
organization and the potential for a few supercells capable of large 
hail and damaging winds. One negative factor for a more robust 
severe event is that low level wind fields are weak (generally less 
than 15 knots in the lowest 2km). This region should remain active 
through the evening, with storms spreading eastward into western MO. 




... 
A fast-moving shortwave trough off the coast of northern California will 
track inland later today, with large-scale lifting beginning to 
affect or before dark. 12z cam solutions suggest the development of 
a few convective cells over central or later this afternoon, 
tracking east-northeastward across the marginal risk area. Forecast 
soundings show inverted-v profiles with sufficient cape to pose a 
risk of damaging winds in the most intense downdrafts. 


$$ 

Mesoscale Discussion

000 
acus11 kwns 162013 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 162012 
moz000-ksz000-162115- 


Mesoscale discussion 1302 
National Weather Service Storm Prediction Center Norman OK 
0312 PM CDT Thu Aug 16 2018 


Areas affected...northeast Kansas...northwest Missouri 


Concerning...severe potential...watch likely 


Valid 162012z - 162115z 


Probability of watch issuance...95 percent 


Summary...scattered strong storms, some producing severe hail and 
gusty winds, are expected within the next few hours. Issuance of a 
Severe Thunderstorm Watch is likely soon. 


Discussion...convective initiation has recently occurred just to the 
west of top, south of a cold front, with additional storms expected 
(as indicated by recent cam guidance) over the next few hours. 
Though directional low-level shear is present, 925-850 mb flow is 
rather weak, with unidirectional shear present mainly above 850 mb. 
Still, steep mid-level lapse rates on the order of 7.0+ c/km, 
resulting in 1500+ j/kg MLCAPE, and 40 knots of effective bulk shear 
suggest that organized updrafts are possible, with large hail a 
concern. A few damaging wind gusts also cannot be ruled out, 
especially given deep moisture throughout the troposphere (pwat 
values over 1.8 inches in many locales), which may promote wet 
downbursts. 


Given the relatively strong forcing for ascent associated with the 
cold front and the propensity for multiple storms to develop in a 
relatively favorable sheared/unstable environment, a Severe 
Thunderstorm Watch will likely be issued for both the highlighted 
area, and the region discussed in mesoscale discussion 1301. 


.Squitieri/Hart.. 08/16/2018 


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


Attention...WFO...eax...top... 


Latitude...Lon 38779537 38929598 39309627 39829620 39929608 39909557 
39969514 40219428 39929361 39449331 38859366 38779537 




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