Convective Outlook

U.S. Severe Weather Forecast

acus01 kwns 231255 
Storm Prediction Center ac 231253 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0653 am CST Fri Feb 23 2018 

Valid 231300z - 241200z 

..there is a marginal risk of severe thunderstorms across a portion 
of the central and northern Texas vicinity.... 

A couple of rounds of thunderstorms will likely affect the Southern 
Plains today and tonight. Very limited risk for an elevated severe 
storm or two may evolve over portions of central/northern Texas just 
prior to -- but more likely after -- the end of the day 1 period 
(saturday morning). 

Some progression of the upper flow field over the U.S. Will occur 
this period, as the western U.S. Trough advances out of the Great 
Basin and across The Four Corners/southern rockies through the 
period. Meanwhile, ridging will persist over the southeast U.S. And 

At the surface, a baroclinic zone will be maintained from the 
Tennessee Valley vicinity to Texas, focusing showers and 
thunderstorms from the Ohio Valley to the Southern Plains through 
the period. of central/northern Texas into adjacent parts of far 
southern Oklahoma... 
a fairly widespread cluster of showers and thunderstorms will affect 
central and northern Texas today, as the center of a short-wave 
trough now crossing the Rio Grande (per the latest WV loop) shifts 
northeast across the Southern Plains. In the wake of this feature, 
after weak/brief short-wave ridging, large-scale height-falls are 
forecast to commence -- particularly during the second half of the 
period -- as the larger-scale western U.S. Trough advances 
into/across The Four Corners and southern rockies. 

As low-level warm advection increases across the Southern Plains in 
response, isentropic ascent atop a still-stable boundary layer will 
eventually fuel development of elevated storms. While most -- if 
not all -- of this convective initiation will likely occur after the 
end of the day 1 period, a storm or two could develop during the 
last 1-2 hours of the period over the central/northern Texas 
vicinity. Any such development would pose some risk for hail, given 
steepening lapse rates aloft and strengthening mid-level flow -- 
both spreading eastward in conjunction with the advance of the main 
upper system. Therefore, will maintain the current/conditional 5% 
risk for hail given the end-of-period potential for convective 
initiation, though greater severe probability will evolve later 
Saturday morning/afternoon. 

.Goss/marsh.. 02/23/2018 


Mesoscale Discussion

acus11 kwns 221211 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 221211 

Mesoscale discussion 0086 
National Weather Service Storm Prediction Center Norman OK 
0611 am CST Thu Feb 22 2018 

Areas affected...portions of central and northern Texas and into 
parts of southern Oklahoma 

Concerning...severe unlikely 

Valid 221211z - 221445z 

Probability of watch issuance...5 percent increase in convection -- including potential for 
marginally severe hail as well as local ice accumulation due to 
freezing rain -- is ongoing across portions of central and northern 
Texas. Ww is unlikely. 

Discussion...latest radar loop shows an increase in elevated showers 
and thunderstorms ongoing across portions of Texas -- particularly 
over The Hill Country and surrounding areas. The storms are 
occurring as large-scale ascent increases across the Southern Plains 
in association with a short-wave trough moving northeastward across 
eastern New Mexico, and within a zone of ample (at least 1000 j/kg) 
cape, elevated atop a layer of near -- or below -- freezing 

Given the aforementioned characteristics of the thermodynamic 
profile, areas of ice accumulation will be possible with briefly 
heavy downpours. Additionally, the degree of cape combined with 
background cloud-layer shear around 50 kt suggests that a few 
organized/possibly rotating storms will be possible, with local risk 
for marginally severe hail with the strongest cells. 

With time, expect this area of showers and storms to spread 
northeastward across North Texas and into Oklahoma, where the lack 
of better cape should mitigate any hail risk but where freezing rain 
-- and thus some ice accumulation -- will still be a concern. 

.Goss/guyer.. 02/22/2018 

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


Latitude...Lon 34259638 32739734 31469777 31219902 30490029 31500073 
32420106 33620078 34560000 35039909 35249784 34909688 

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