U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 180052 
Storm Prediction Center ac 180051 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0751 PM CDT Friday Apr 17 2015 

Valid 180100z - 181200z 

..there is a slight risk of severe thunderstorms over the central Great 

..there is a slight risk of severe thunderstorms over south Texas... 

..There is a marginal risk of severe thunderstorms across portions of the plains 
and central Gulf Coast... 

Severe thunderstorms will continue across the central Great Plains 
and across parts of south Texas. Threats will include large 
hail...damaging winds and a few tornadoes. 

..central Great Plains... 

Upper low is expected to migrate slowly eastward across Colorado to near the 
Front Range by sunrise. Southeasterly boundary layer flow should therefore 
persist across the High Plains and convective threat should persist 
well into the overnight hours. 00z sounding from ddc exhibits 
substantial veering profiles and speed shear with height and more 
than adequate buoyancy for robust updrafts. Isolated supercells and 
perhaps a few tornadoes can be expected with this activity. 
Otherwise...large hail is the primary threat. 

Farther south...dry line has retreated westward across the Texas Panhandle 
and convection is deepening along this moisture surge. Have 
adjusted mgrl severe threat westward to account for this activity. Reference 
mesoscale discussion #345 for more information. 

..south Texas... 

Well organized mesoscale convective system has progressed across scntrl Texas into the Upper Texas 
coastal region. Trailing this activity...scattered supercells extend southwestward 
in vicinity of wind shift toward Webb County. Given the upward trends in 
deep convection it appears severe threat will linger across this 
region well into the evening hours. 00z sounding from crp supports 
this with moderate instability and strong surface-6km bulk shear. 
Isolated tornadoes can not be ruled out with the strongest activity. 

.Darrow.. 04/18/2015 

Mesoscale Discussion

acus11 kwns 180448 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 180448 

Mesoscale discussion 0352 
National Weather Service Storm Prediction Center Norman OK 
1148 PM CDT Friday Apr 17 2015 

Areas affected...southwestern Nebraska 

Concerning...Tornado Watch 69... 

Valid 180448z - 180545z 

The severe weather threat for Tornado Watch 69 continues. 

Summary...overall severe risk continues to diminish and an 
additional ww is not expected. 

Discussion...convection has largely weakened...but still persists 
within valid portion of ww 69 over southwestern Nebraska. Given a 
cooling/stabilizing boundary layer...the tornado risk has become 
negligible. With only modest effective shear amidst meager 
buoyancy...hail size will likely remain sub-severe through 06z. 

.Grams.. 04/18/2015 

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


Latitude...Lon 41310112 41030049 40720031 40430041 40410081 40440099 
40840145 41190156 41310112