Satellite imagery and surface observations indicate that widespread fog with isolated areas of dense fog is in place across much of Deep South Texas and the Rio Grande Valley at this time. Visibilities are generally reduced to between 1 and 3 miles, with isolated areas of dense fog reducing the visibility to one half of a mile or less. This fog is likely to persist until shortly after sunrise this morning. Motorists are urged to reduce speed, use low beam headlights, and avoid tailgating in any fog through the next several hours.