U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 241618 
Storm Prediction Center ac 241617 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1117 am CDT Wed Apr 24 2019 

Valid 241630z - 251200z 

..there is a slight risk of severe thunderstorms through early 
tonight from south central into southeast Texas and western la... 

Thunderstorms associated with large hail, wind damage and a tornado 
threat are expected to develop across parts of south-central and 
southeast Texas today into western Louisiana tonight. 

..south central/southeast Texas into western la through tonight... 
A midlevel shortwave trough over northern Mexico will translate 
eastward to central/East Texas by the end of the period. Weak surface 
cyclogenesis is expected along stalled baroclinic zone across 
central Texas in advance of the midlevel trough. However, the surface 
pattern is complicated by convective outflow that is still moving 
southeastward past San Antonio as of late morning. The primary 
corridor of severe-storm threat this afternoon into tonight should 
be along this outflow boundary from south central into southeast Texas. 

Boundary-layer dewpoints of 67-70 f and surface heating in cloud 
breaks (beneath midlevel lapse rates greater than 8 c/km) will drive 
MLCAPE of 1500-2000 j/kg. Deep-layer vertical shear will be 
favorable for supercells, with an increase in low-level shear 
expected immediately east of the ejecting midlevel trough and weak 
surface wave. Storm Mode will likely be a mix of 
clusters/supercells this afternoon, growing into a qlcs by this 
evening. Low-level shear/hodograph curvature will favor some 
tornado threat with supercells/clusters along the residual outflow 
boundary and adjacent northern part of the warm sector. Damaging 
winds and large hail will also be possible with this convection into 
tonight as it reaches the Texas/la border region. 

..northeast Wyoming and vicinity this afternoon... 
A mid-upper speed Max is cresting the larger-scale ridge and will 
move east-southeastward over the northern High Plains this 
afternoon/evening. Despite marginal low-level moisture, 
sufficiently steep low-midlevel lapse rates will support some 
low-topped convection this afternoon in advance of the midlevel 
trough. Gusty winds will be possible given the steep low-level 
lapse rates/evaporational cooling potential, though severe winds 
appear unlikely. 

.Thompson/squitieri.. 04/24/2019 


Mesoscale Discussion

acus11 kwns 241512 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 241511 

Mesoscale discussion 0432 
National Weather Service Storm Prediction Center Norman OK 
1011 am CDT Wed Apr 24 2019 

Areas affected...central into southeastern Texas 

Concerning...severe potential...watch possible 

Valid 241511z - 241715z 

Probability of watch issuance...40 percent 

Summary...a ww issuance may be needed in portions of the discussion 
area - most likely from 16z Onward. 

Discussion...mostly sub-severe convection continues currently amidst 
a complicated surface pattern, with a remnant outflow extending from 
near cll to 40 S Sat to near drt. Surface-based convection persists 
near the outflow, with one dominant cell over western Gonzales 
County exhibiting signs of mid-level rotation. Though low-level 
wind fields remain weak, any favorable interaction between updrafts 
associated with this convection along the remnant outflow may result 
in a brief tornado. 

Over time, strengthening low-level wind fields associated with 
low-level cyclogenesis and approach of a mid-level wave centered 
over northern Mexico will probably result in 1) stalling and/or slow 
northward retreat of the outflow and 2) gradually increased 
organization of convection. Any storms near/south of this outflow 
will be surface-based owing to near 70f dewpoints, while steepening 
mid-level lapse rates will increase buoyancy and result in an 
increased threat for all modes of severe. North of the boundary, a 
gradually organizing linear complex near sjt and other scattered 
convection near hdo/Sat/aus may pose a threat for marginally severe 
hail and perhaps an isolated damaging wind gust. Convective trends 
continue to be monitored, and a ww issuance may be needed at some 
point after 16z or so. 

.Cook/Thompson.. 04/24/2019 

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


Latitude...Lon 31460105 31520008 31419820 31049668 30489576 29839546 
28879575 28309648 27949798 27949940 28350026 29170094 
29720142 30350162 31040137 31190130 31460105