Ice, Not Nice: Glaze Coats Lower Rio Grande Valley on January 29th, 2014

Photos taken from around the Rio Grande Valley on January 29, 2014. Credits: NWS Employees, Emergency Management Personnel, and Social Media Followers.

Ice, Not so Nice
Second Ice Storm in Three Years Coats Trees, Powerlines, etc. in Glaze

January 29, 2014 Event Brings Back Memories of February 2011

Loop of 2.4° reflectivity across Cameron, Willacy, and eastern Hidalgo County between 4 and 6 AM January 29 2014. Orange and red colors indicate a combination of large raindrops and ice pellets; much of the rain froze on contact with exposed, elevated surfaces.

Summary
For the first time since February 3rd and 4th 2011, an icy glaze coated much of the Rio Grande Valley from the pre–dawn hours through late morning of January 29th, 2014. The glaze, left behind when ½ to just under 1 inch of rain froze on contact with exposed surfaces such as trees and grasses, power lines/poles, fences, vehicles, roofs, and more. The rain also created some icing on elevated highways and bridges. Unlike the event in 2011, which featured a nearly 24 hour drizzle that fell with temperatures several degrees below freezing and accreted to more than one inch in much of Cameron County, this event began as plain rain with temperatures several degrees above freezing. As the rain fell into the very dry air, temperatures quickly fell to around freezing, probably a little lower immediately around exposed surfaces; soon after, ice began to accrete. By the time the precipitation ended, generally around 7 AM across the mid Valley and a little after 8 AM on the coast, between 1/8 inch and 1/2 inch of ice accreted (below). The rain mixed with ice pellets (sleet) at times (above), particularly between 4 and 6 AM. Across the Upper Rio Grande Valley, Rio Grande Plains, and Deep South Texas Ranchlands, patchy light sleet and freezing drizzle were little more than a conversation starter, with limited or no impact.

In addition to the freezing temperatures and nasty precipitation, a stiff north wind, gusting over 25 mph at times across the Lower Valley and beaches, dipped the wind chill, or "feels–like" temperature, into the low to mid 20s for the second time in five days (below). The cold blase, one of three notable snaps in January, ensured a third consecutive month of significantly (~2°F or more) below average temperatures across the Rio Grande Valley for the first time in many years.

Top: Minimum temperatures on January 29th. Note the higher values farther north; the lack of precipitation combined with insulating cloud cover kept readings well above freezing compared to locations in the Rio Grande Valley. Bottom: Minimum "Feels like" (wind chill) temperatures on January 29th. Most occurred during the 3 to 8 AM period.

Top: Special atmospheric sounding taken at Brownsville between 11 PM January 28 and midnight January 29. Note the "nose" of warm air (green shade) which melted developing snow above into rain, which then refroze in some areas (sleet) or reached elevated surfaces and froze (glaze). Bottom: Atmospheric sounding taken at Brownsville between 5 AM and 6 AM January 29th. The "nose" was still evident, though had shrunk noticeably. Despite the smaller melting layer, the layer was enough to kill off any chance for snow at the ground.

Across the Valley, generally minor inconveniences were noted, mainly from power outages. There will likely be some damage to young, tender tropical plants weighed down by the ice. Impacts were likely limited due to advance notice to schools, transportation managers, and utility companies who were given 12 hours of notice to make proactive decisions ahead of the first reports of icing. These decisions and impacts included:

School Delays. Virtually all districts delayed classes until 9 or 10 AM, which allowed for melting (and daylight) to keep bus drivers and students safe from potential dangers of icy patches on rural bridges and overpasses.
Road Closures. The Texas Department of Transportation closed all elevated expressways and ramps across the Rio Grande Valley prior to the onset of the glazing. Reports indicated several icy patches through what would have been a typically busy morning commute (6 to 9 AM). Traffic was redirected to the frontage roads, which were not impacted by the precipitation due to warm soil temperatures. One accident was reported on a non–elevated road in McAllen that took a life and injured three others; ice was not a cause.
Power Disruption. News reports indicated 12,000 customers were without electricity during the peak of the storm early on the 29th, in Port Isabel, Bayview, Harlingen, San Benito, and other communities.
Plant and Crop Damage. On first inspection, most hearty plants quickly sprung back after being weighted down by the ice (video, below). There was likely some damage to tender tropical vegetation (such as banana plants, bougainvillea, etc.) but many of these plants should recover.

What Happened to the Snow...and most of the Sleet? The ice storm was produced from a combination of cold high pressure near the earth’s surface combined with an upper level disturbance that moved across northern Mexico from late on the 28th through the early morning of the 29th. Model forecast trends through the morning and early evening of the 28th edged more towards sleet than glaze ice, as temperatures in the precipitation production zone (generally between 5 and 20 thousand feet) were expected to sit right along the freezing line. The upper disturbance, energetic enough to produce afternoon thunderstorms over the Sierra Madre Occidental in Durango and Chihuahua State (Mexico), likely weakened just enough to reduce the lift necessary to cool the entire column – even for a couple hours – to produce snowflakes. The 6 AM sounding (above, second image) showed just how close the region was to seeing a brief changeover and the first snow since Christmas 2004. Alas, it was not to be.

Map of measured and estimated ice accretion prior to melting (8 AM or so) January 29, 2014

Measured and estimated ice accretion and impact map for the January 29, 2014 winter weather event. Data courtesy of NWS employees, Emergency Management and related staff, local media, and social media friends.

Time lapse of icicle development and icing at the Lone Star National Bank in Brownsville, January 29, 2014

Time lapse of icicle development and icing at the Lone Star National Bank in Brownsville, January 29, 2014

Time lapse of ice storm as seen from the Lone Star National Bank at the intersection of Boca Chica Boulevard and U.S. 77/Interstate Highway 69E (Expressway) in Brownsville, generally from midnight to noon on January 29th 2014. Note the icicle development and melt, and the weighting down of the palm trees (lower left) before "springing" back after melting is completed. Images courtesy of Weatherbug, Inc..

Precipitation map for the Rio Grande Valley January 28 January 29, 2014

January 28/29 Precipitation Totals for Selected RGV Locations
City/Town	County	Precipitation (as Liquid, inches)
Harlingen 2.6 ESE	Cameron	0.88
San Benito 0.6 SSE	Cameron	0.84
San Benito 7.8 E	Cameron	0.80
Harlingen 3.1 SSW	Cameron	0.80
Harlingen 0.4 N	Cameron	0.73
Brownsville 1.5 WNW	Cameron	0.73
Harlingen/Cooperative	Cameron	0.70
La Joya/Cooperative	Hidalgo	0.70
South Padre Island 1.1 N	Cameron	0.68
Port Isabel	Cameron	0.64
McAllen 2.4 NE	Hidalgo	0.63
Los Fresnos 0.3 NE	Cameron	0.63
South Padre Island/Isla Blanca Coop	Cameron	0.62
Pharr 5.1 N	Hidalgo	0.61
Raymondville 2.0 SSW	Willacy	0.61
Mission 1.9 ENE	Hidalgo	0.58
Santa Rosa	Cameron	0.52
Brownsville/SPI International Airport	Cameron	0.52
Port Mansfield	Willacy	0.51
Laguna Vista 0.3 N	Cameron	0.51
Edinburg/Cooperative	Hidalgo	0.50
San Manuel	Hidalgo	0.35
Rio Grande City	Starr	0.30
Armstrong 0.4 E	Kenedy	0.23
Sarita 7 E	Kenedy	0.12
Falfurrias (West)	Brooks	0.07