The combined effects of a developing subtropical jet stream, a weak  upper level disturbance propagating northeastward from Mexico, a weak surface boundary moving south into Deep South Texas, and a very unstable atmospheric profile across the western Lower Rio Grande Valley and Rio Grande Plains, produced strong to severe thunderstorms over northern Mexico and the western and central counties of the Lower Rio Grande Valley during the late evening of May 14th.

Hail in ZAPATA, TEXAS
From 14-MAY-08 19:59:00 to 14-MAY-08 20:14:00 (CST-6)
Location: ZAPATA ARPT
Magnitude: 1.00 
Reported by: Public

The public reported that nickel to quarter size hail continued to fall across much of the city of Zapata.  The event, which began at 8:43 PM CDT, may have lasted for a total of 40 minutes in some locations in and around Zapata.

Thunderstorm Wind in ZAPATA, TEXAS
From 14-MAY-08 19:50:00 to 14-MAY-08 20:05:00 (CST-6)
Location: ZAPATA ARPT
Magnitude: 65.00 EG
Property damage: 750.00K
Reported by: NWS Storm Survey

Damage from the microburst was first surveyed about 2 miles west of the center of town along and near Farm to Market (FM) Highway 496. In the neighborhood of Falcon Mesa, along FM 3074, numerous barrel tiles were torn from the roof; in the same neighborhood, numerous large limbs from ebony and live oak trees were blown down, and minor damage to roofs was noted at other homes.  Similar tree and roof damage was noted at another neighborhood along Oak Street, just south of the Zapata Cemetary.
Farther east along FM 496, several large fiberglass storage tanks were rolled, and damaged beyond repair, at a facility between FM 3074 and the Zapata County cemetary. On the same property, a manufactured home had numerous holes in its west facing wall, from wind driven pebbles and stones. The same home had fairly significant asphalt shingle damage to its roof. A nearby low metal tower was bent in half.
The worst-looking damage was seen just west of the center of town, along FM 496 only 1/3 mile west of the intersection of Federal Highway 83.  Here, significant damage was incurred to many units at the Highway 496 Storage facility.
The microburst slammed into the west facing wall of the first of two long, cinderblock structures, and lifted most of the roof up and over the first building, slamming it into the second building about 50 feet to the east. While the truss and bracing of the roof appeared sound, only long nails were found at the connections of the eaves. Missiles generated by the broken roof drove into both cinderblock, and an individual metal garage, in the second building. Another light metal structure, housing another set of individual storage units, separated and collapsed on the leeward side of the second building.
The microburst continued moving steadily southeast, causing notable damage to neighborhoods in the southwest part of town. Dozens of homes and other structures with poorly anchored roofing material sustained significant damage; a large portion of tin roof was removed from a two story church a few blocks from the center of town. Another barrel-tile roof was damaged at a motel, and the water leak caused at least one unit to be uninhabitable.
In all neighborhoods, hundreds of mesquite and ebony tree limbs of many shapes and sizes were snapped off, some onto roofs, including the town's public library.  As the storm finally edged south, additional tree damage was noted in the Falcon Lake Estates subdivision, just south of the bridge, where a report of a blown down roof of a two story house was also received as the storm weakened slightly.
The Zapata County Emergency Manager reported power lines and several trees were down in Zapata and approximately 200 to 300 people were without power at 9 pm.
Wind speeds were estimated to be between 70 and 75 mph area wide, with the strongest speeds generally along and just south of FM 496 from just west of the cemetary to highway 83.  Total path length was estimated to be a little more than 3.5 miles long; width was estimated to be about 1.5 miles.

Thunderstorm Wind in STARR, TEXAS
From 14-MAY-08 21:30:00 to 14-MAY-08 21:35:00 (CST-6)
Location: ROMA
Magnitude: 50.00 EG
Property damage: 5.00K
Reported by: Law Enforcement

Law enforcement in Starr County reported power lines down and power outages occurred in Roma due to high winds from strong to severe thunderstorms in and near the area.

Thunderstorm Wind in BROOKS, TEXAS
From 14-MAY-08 20:57:00 to 14-MAY-08 21:00:00 (CST-6)
Location: ENCINO
Magnitude: 50.00 EG
Property damage: 5.00K
Reported by: Law Enforcement

Law enforcement in Brooks County reported power lines down and power outages near Encino due to a thunderstorms moving through the area with high winds.

Hail in ZAPATA, TEXAS
From 14-MAY-08 19:43:00 to 14-MAY-08 19:58:00 (CST-6)
Location: ZAPATA ARPT
Magnitude: 1.00 
Reported by: Emergency Manager

Zapata County emergency manager reported quarter size hail fell in downtown Zapata. The public also reported quarter size hail with some even larger hail stones fell in Zapata.

Thunderstorm Wind in STARR, TEXAS
From 14-MAY-08 20:41:00 to 14-MAY-08 20:41:00 (CST-6)
Location: EL SAUZ
Magnitude: 55.00 EG
Property damage: 1.00K
Reported by: Law Enforcement

Law enforcement in Starr County reported numerous trees blown down on FM 649 near El Sauz.

Thunderstorm Wind in STARR, TEXAS
From 14-MAY-08 20:48:00 to 14-MAY-08 21:03:00 (CST-6)
Location: VIBORAS
Magnitude: 55.00 EG
Property damage: 2.00K
Reported by: Law Enforcement

Power lines down, and power outages, were reported across a large part of Starr County as a developing line of severe thunderstorms moved through.  One of the strongest cells likely produced some of these power outages between Viboras and La Gloria along Farm-to-Market road 2686.

Hail in ZAPATA, TEXAS
From 14-MAY-08 20:15:00 to 14-MAY-08 20:25:00 (CST-6)
Location: ZAPATA
Magnitude: 1.75 
Reported by: Public

The public reported hail up to 1.75 inches was observed falling approximately 6 miles southeast of Zapata along US highway 83, as the supercell thunderstorm began edging toward Starr County.