A blast of very dry air, fed by strong northwest flow at all levels of the atmosphere that originated from the Pacific, rather than the North Pole, surged through the southern Rockies and Sierra Madre Oriental on its way to south Texas and the Rio Grande Valley on January 11th, 2018. Downslope flow during the afternoon of the 11th pushed temperatures well into the 80s, but dropped humidity into the teens as northwest winds picked up to 15 to 25 mph, on average.
The true front arrived by mid to late afternoon across the Rio Grande Plains and South Texas Brush Country ranchlands, then surged into the Rio Grande Valley from sunset through 11 PM. Very strong winds, as high as 60 mph just above the surface, slammed into the region, creating scattered power outages, a number of grass fires, and localized wind damage to trees, power poles, and some roofs. Downed power lines caused numerous small grass fires between Edinburg and Mission, with additional small trees/limbs down in Combes (near Harlingen). At Brownsville/South Padre Island International Airport, a blown down line sparked a small wildfire just down the road from the NWS office. Sustained winds of 25 to 35 mph with frequent gusts ranging|from 40 to nearly 55 mph lasted for about three hours in most inland locations, but up to nine hours along the Lower Texas coast, where the moderate gale persisted well into the night of the 11th and into the pre-dawn hours of the 12th|. |Preliminary power outage statistics across the Valley suggested between 3,000 and 5,000 customers lost power during the peak of the gusts, based on preliminary reports from local power providers.