Special Weather Statement issued April 21 at 4:24AM CDT by NWS Brownsville TX

Surface observations across Deep South Texas and the Rio Grande
Valley indicate that isolated patches of dense fog are developing
and persisting within the region at this time. Visibilities are
being reduced to one half mile or less where this dense fog is
forming.

Motorists are encouraged to reduce speed, use low beam headlights,
and avoid tailgating in any fog through the next few hours and
especially during the morning commute to work and school.