U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus02 kwns 210601 
Storm Prediction Center ac 210600 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0100 am CDT Thu Jun 21 2018 

Valid 221200z - 231200z 

..there is a slight risk of severe thunderstorms from eastern 
Colorado into northwest Oklahoma...and from the arklatex into middle 

Scattered severe storms are expected across parts of the Central 
High plains, and from the lower Mississippi Valley into the Ohio 

An upper low will move from the middle MS valley toward the lower 
Great Lakes, with a broad area of cyclonic flow aloft lifting from 
the lower MS valley toward the mid Atlantic. A surface low will move 
slowly from Illinois into in, with a cold front extending from the lower 
Ohio River southwestward into southern Arkansas at 00z. To the west, a 
progressive shortwave trough will move across The Rockies and into 
the Central Plains, with a surface low developing over the OK and Texas 
panhandles. Both of these features aloft will support area of strong 
to severe thunderstorms on Friday. 

..eastern Colorado into northern OK... 
Low pressure will deepen over the southern High Plains during the 
day with surface convergence maximized from the Colorado Front Range 
southward into the OK and Texas panhandles during the afternoon. Low 
50s f dewpoints are expected over Colorado which will support moderate 
instability given cooling aloft with the shortwave trough. 
Hodographs will be straight, and supportive of long-lived cells 
capable of large hail. Southern parts of the area will be more 
unstable, and will have larger looping hodographs supporting 
supercells capable of producing very large hail. Damaging wind is 
also likely during the evening and overnight if cells can merge into 
a cluster or mesoscale convective system. This potential mesoscale convective system would then travel eastward 
across much of OK and perhaps southern KS, supported by a low-level 
jet and the progressive shortwave trough. The slight risk has the 
potential to be expanded eastward as predictability for this 
scenario increases. 

..lower MS valley into the Ohio Valley... 
A moist and unstable air mass will exist east of the front, with the 
most unstable air across the lower MS valley. Bouts of thunderstorms 
are possible throughout the day, but the most substantial storms 
should be during the afternoon when instability is maximized beneath 
favorable flow aloft. While southern areas will be most unstable, 
there may be some midlevel subsidence on the back side of the upper 
trough. Damaging winds and marginal hail will be possible. A few 
supercells are possible as well, and a brief tornado cannot be ruled 

..maximum risk by hazard... 
Tornado: 2% - marginal 
wind: 15% - slight 
hail: 15% sig - slight 

.Jewell.. 06/21/2018