U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 161632 
Storm Prediction Center ac 161630 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1130 am CDT Mon Jul 16 2018 

Valid 161630z - 171200z 

..there is a slight risk of severe thunderstorms across portions of 
Wyoming and the Central High plains... 

Scattered severe storms are expected across parts of the Central 
High plains and Black Hills regions from late afternoon into 
tonight. Large hail and strong to severe wind gusts should be the 
main hazards. 

..intermountain West/Wyoming to Central High plans... 
A perturbation embedded within a low-amplitude shortwave trough over 
the Pacific northwest will move east from southern Idaho towards the 
Central High plains through this evening with a subtle disturbance 
or two preceding this more discernible mid-level impulse. Related 
weak large-scale ascent in conjunction with a moist air mass, with 
prevalent 60s f surface dewpoints across the High Plains, will lead 
to widely scattered storm development by mid/late afternoon. Such 
development is likely to initially occur over the intermountain west 
to interior Wyoming, and potentially as far east as the Black Hills 
vicinity and southwest/south-central South Dakota by late afternoon. 

Semi-elongated hodographs (aided by 40+ kt high-level winds at 7+ km 
agl) are anticipated to overlap with the eastern periphery of the 
elevated mixed-layer characterized by steep mid-level lapse rates. A 
moderately buoyant air mass is expected mainly from east-central/far 
southeast Wyoming into southern South Dakota and much of 
west/central Nebraska. The setup should favor a few discrete 
supercells, the most sustained of which may be those that move 
south-southeast from western/southern South Dakota into the Nebraska Panhandle 
and/or northern Nebraska. Large hail along with isolated severe wind 
gusts should be the primary hazards. 

During the evening, this activity will likely grow upscale as 
moderate low-level southerlies strengthen to around 30 kt over the 
Central High plains. This should result in a 
south/southeastward-propagating cluster with mainly a strong to 
isolated severe wind risk in western Nebraska before weakening 
overnight in the northwest Kansas/northeast Colorado vicinity. 

..eastern Great Lakes... 
In advance of an eastward-moving front, scattered thunderstorm 
development is expected this afternoon across lower Michigan to the 
Lee of lakes Erie/Ontario. Convergence is generally weak and 
stronger mid-level westerlies will lag behind the surface cold 
front, although brief overlap of the warm sector with modest 
effective shear values may support some sustained/briefly organized 
storms. With weak mid-level lapse rates and unfavorable nocturnal 
timing of frontal impingement east of the lower lakes, the overall 
setup is expected to only yield localized strong gusts capable of 
tree damage. 

..southeast Kansas/northeast Oklahoma to the Ozarks... 
Small-scale cold pools and zones of differential heating will likely 
influence additional storm development and intensification across 
the region within a very moist and diurnally destabilizing boundary 
layer. Given the degree of heating/moisture and resultant buoyancy, 
it is conceivable that a couple of the wet microbursts could produce 
localized wind damage this afternoon. 

.Guyer/Wendt.. 07/16/2018 


Mesoscale Discussion

acus11 kwns 161921 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 161920 

Mesoscale discussion 1059 
National Weather Service Storm Prediction Center Norman OK 
0220 PM CDT Mon Jul 16 2018 

Areas affected...portions of eastern OK...southwestern MO...and 
northern/central Arkansas 

Concerning...severe potential...watch unlikely 

Valid 161920z - 162145z 

Probability of watch issuance...5 percent 

Summary...scattered thunderstorms may pose a very isolated threat 
for strong to damaging winds through the remainder of the afternoon. 
Watch issuance is not expected. 

Discussion...a pair of mcvs are present across southeastern Kansas and 
northeastern OK this afternoon per recent visible satellite and 
radar imagery. An outflow boundary associated with prior convection 
from one of these circulations is encouraging renewed thunderstorms 
across far northeastern OK and vicinity as of 1920z. Although winds 
through the troposphere will remain weak based on rap mesoanalysis 
and vwps from area radars, a hot/unstable airmass characterized by 
2000-2500 j/kg of MLCAPE will support strong updraft growth in the 
initial thunderstorm stage. Water-loaded downdrafts may pose a 
strong to damaging wind threat, and a storm just northwest of Little 
Rock, Arkansas showed a brief but clear downburst signature with around 50 
kt inbound velocities less than 500 ft above ground level from 1900-1910z. Any 
thunderstorm in this environment should be capable of producing 
similar strong to severe downburst winds. There may be some 
potential for storms to congeal into one or more very loosely 
organized clusters along the outflow boundary across far 
northeastern OK into southwestern MO and northwestern Arkansas over the 
next few hours. If this were to occur, then perhaps a slightly 
greater wind threat may be realized. Regardless, the lack of 
meaningful shear will very likely keep the severe threat too 
isolated to justify a watch. 

.Gleason/guyer.. 07/16/2018 

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


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