U.S. Severe Weather Forecast (Convective Outlook)

Day Three

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Storm Prediction Center ac 251934 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0234 PM CDT Wed Apr 25 2018 

Valid 252000z - 261200z 

..there is a marginal risk of severe thunderstorms for the 
Lower/Middle Rio Grande Valley... 

Isolated strong/severe thunderstorms may affect primarily the 
Lower/Middle Rio Grande Valley region of south Texas. 


No appreciable changes are warranted to 1630z outlook. 

Strong surface heating is confined to regions west of the Rio Grande 
River and this has contributed to an axis of MLCAPE upwards of 2000 
j/kg in the Lee of the Sierra Madre orientals. Strong convection is 
evolving over the higher terrain and will soon spread toward lower 
elevations. However, it appears the strongest activity should 
struggle to spread east of the international border. For these 
reasons will maintain 5% severe probs for the U.S. Side of the 
Lower/Middle Rio Grande Valley. 

.Darrow.. 04/25/2018 

Previous discussion... /issued 1052 am CDT Wed Apr 25 2018/ 

A strong cold front is surging southward across The Big Bend region 
of TX, and is spreading eastward through The Hill Country. 
Scattered elevated thunderstorms are occurring immediately behind 
the front, with the potential for hail in the stronger cells 
throughout the day. The air mass ahead of the front continues to 
moisten and destabilize, with afternoon MLCAPE values expected to be 
around 2000 j/kg. It appears likely that a few severe thunderstorms 
will affect parts of northern Mexico, with some severe threat 
extending northward into the Rio Grande Valley of Texas. At this time, 
12z guidance and trends in observational data continue to support 
that the overall risk in central/south Texas is marginal, but an 
isolated storm or two could produce large hail and/or damaging winds 
this afternoon and evening. 


Mesoscale Discussion

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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 252024 

Mesoscale discussion 0289 
National Weather Service Storm Prediction Center Norman OK 
0324 PM CDT Wed Apr 25 2018 

Areas affected...parts of south Texas 

Concerning...severe potential...watch unlikely 

Valid 252024z - 252230z 

Probability of watch issuance...20 percent 

Summary...a severe storm or two -- with potential to produce hail 
and/or locally damaging winds. Ww is not anticipated at this time 
due to anticipated limited coverage of risk. 

Discussion...latest radar loop shows a cluster of thunderstorms near 
and west of the Sat area, along a cold front moving steadily 
southward across south Texas. Other, stronger cells are ongoing 
well west of the Rio Grande over northeast Mexico -- where much 
greater instability is observed. 

With that said, the eastern extension of the axis of stronger 
instability extends just across the river into Laredo/Cotulla area, 
south of the ongoing storms. As the front advances southward into 
this area, a couple of more vigorous storms may develop. While 
shear remains somewhat modest across the area -- only marginally 
supportive of mid-level rotation, some risk for hail and or damaging 
winds may evolve locally late this afternoon and early evening. 

.Goss/Hart.. 04/25/2018 

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


Latitude...Lon 28340028 28790019 29679882 29549815 29049810 27539903 
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