January 8th 2010 winter weather impacts:  Gales in the water, a wintry mix near the coast, and frigid wind chills everywhere (click to enlarge)
Behold the Polar Express!
Arctic Airmass Bringing Winter’s Chill to Deep South Texas

Overview
After a long hiatus from a true arctic outbreak in Deep South Texas, very cold temperatures began to invade Deep South Texas during the afternoon of January 7th, as temperatures dropped sharply from the 60s into the 40s and wind chill values fell into the upper 30s and lower 40s before sunset. The arctic air will continue to plunge southward into the weekend, continuing through Sunday morning, January 10th. Prolonged cold to frigid temperatures, a widespread hard freeze, and even an opportunity for a wintry mix of precipitation in the Lower Rio Grande Valley is expected for the first time since the 2004 White Christmas – which began as a mix of rain and sleet on Christmas Eve. Unlike the Christmas Eve event and a prior very cold and brisk day back on January 14th, 1997, the upcoming episode will feature very dry air, particularly a little ways inland from the coast. This dry air may exacerbate problems for tender vegetation, particularly tropical plants, unharvested citrus fruits, and sugar cane. Wind chill values may become critical for local residents planning to spend any length of time outdoors without proper clothing.

Freezing temperatures will arrive from Zapata through Hebbronville, Falfurrias, and Sarita between midnight and 3 AM on January 8th, and continue spreading south and east, reaching the Rio Grande Valley except for the immediate coast between 3 and 6 AM. Coldest temperatures, and wind chill values, are expected to begin the work and school day on Friday, January 8th.

January 8th: Brrrr!
Brisk north winds will continue spreading very cold air across Deep South Texas, while a vigorous jet stream races into the region 30,000 feet above the ground. This jet will draw a thick high overcast across the entire region, ensuring that temperatures hold in the 30s, in some cases more than 30°F below average! Across the Lower RGV, this jet will enhance a developing pool of moisture below 10,000 feet, enough to allow precipitation to fall from the pre dawn hours into the afternoon. Precipitation amounts should be light, but the type of precipitation will be driven by the continued cooling of the column below 10,000 feet. Forecast data indicate sleet is possible in a small area of the Lower RGV, extending from extreme eastern Hidalgo County through much of Cameron into southeastern Willacy County from early in the morning until mid afternoon. The best chances for any precipitation are east of Highway 77; however, the location could change as the event approaches. The lower clouds and associated precipitation will hold temperatures within a few degrees of the freezing point from Weslaco through Brownsville and Port Isabel. Elsewhere, thick mid and high clouds wil allow slight warming between Noon and 3 PM, with temperatures approaching 40 or so from western Hidalgo across the Rio Grande Plains. Added wind will make it feel more like 15 to 25 across many areas of Deep South Texas to start the day; these conditions will ensure that January 8th will be the coldest calendar day in Deep South Texas since December 24th, 2004.

Dangerous winds and large seas and swells will impact the Gulf and Laguna waters on the 8th. Gale force gusts will combined with healthy seas up to 15 feet, and a miserable light rain to make for conditions unfit for man or watercraft in the open Gulf; waves up to 2 or 3 feet in the center channel of the Laguna Madre between South Padre Island and Port Isabel will roughen up the waters in the normally more placid bay.

January 9th/10th 2010 winter weather impacts:  Hard freezes, frosts will impact agriculture (click to enlarge)

January 9th/10th: Hard Freeze, Hard on Nature
As a branch of the arctic high pressure center (below) settles into Deep South Texas beginning on January 9th, skies will clear and temperatures will drop below 28°F for at least several hours, for all areas except the immediate coastline and communities within 20 miles or so of the coast, where the freeze will be leavened by the proximity to the warmer Gulf. Cold air continuing to funnel south will maintain very low dew point temperatures, from the single numbers to the lower teens, in some fertile agricultural districts. The combination of subfreezing temperatures with a bit of wind and very dry air will increase the impact on tender tropical vegetation, as any nearby moisture will evaporate quickly, cooling the vegetation even more. Further information on cold weather impacts and crop protection can be found here.

Expected durations of temperatures ≤32°F, and readings ≤27°F (defined as a hard freeze, for the overnight of January 8th into January 9th are as follows:

For the Lower and Middle Valley:
    Temperatures ≤32°F:
  • Inland, non urban cores: 6 to 9 hours, 12 hours in sheltered locations
  • Near coast, urban cores: 2 to 4 hours, 6 hours in sheltered locations
    Temperatures ≤27°F (Hard Freeze):
  • Inland, non urban cores: 3 to 6 hours, 9 hours in sheltered locations
  • Near coast, urban cores: Up to 2 hours, 4 hours in sheltered locations

For the Upper Valley and Rio Grande Plains:
  • Temperatures ≤32°F: 9 to 12 hours, 15 hours in sheltered locations
  • Temperatures ≤27°F: 4 to 8 hours, 12 hours in sheltered locations

The freeze on January 10th will be of the "frosty" variety, but still critically cold nonetheless as high temperatures on the 9th struggle to get much above 45°F, opening the door for rapid cooling under clear skies and calm winds overnight. Minimum temperatures on the 10th should reach their lowest values of the weekend in many areas before conditions warm up back to the merely cool 50s during the afternoon. For the 9th and 10th, daily record low temperatures will be threatened; for many locations, the prior record lows range from the mid to upper 20s.

Expected durations of temperatures ≤32°F, and readings ≤27°F (defined as a hard freeze, for the overnight of January 9th into January 10th are as follows:

For the Lower and Middle Valley:
    Temperatures ≤32°F:
  • Inland, non urban cores: 3 to 6 hours, 10 hours in sheltered locations
  • Near coast, urban cores: 1 to 2 hours, 4 hours in sheltered locations
  • *Readings may briefly touch 32 along the coast (i.e. Port Isabel).
    Temperatures ≤27°F (Hard Freeze):
  • Inland, non urban cores: 2 to 4 hours, 6 hours in sheltered locations
  • Near coast, urban cores: Up to 1 hour, 2 hours in sheltered locations

For the Upper Valley and Rio Grande Plains:
  • Temperatures ≤32°F: 6 to 12 hours, 15 hours in sheltered locations
  • Temperatures ≤27°F: 5 to 9 hours, 12 hours in sheltered locations

Tips to Keep Your Family, Pets, and Plants Safe

  • Bundle Up!. Wear several layers of warm clothing rather than a single coat or jacket. Wear a hat and gloves, and protect your face from the wind with a scarf. Get these items together now; don’t wait until the last minute.
  • Take Pets Inside. Animals, too, get acclimated to warmer climates. Keep cats indoors, and take dogs for brief walks and do not leave them outside during the cold snap.
  • Use Heaters Safely. If you use space heaters or other non conventional methods to keep warm indoors, remember to check to see if the equipment is listed by Underwriters’ Laboratories and is in good working condition. Do not use any open heating device around combustible objects. Never use ovens, stoves or barbeque grills for heat.
  • Check those Pipes!. Particularly for outdoor and rooftop plumbing. Insulate as much as possible now. Friday and Saturday night may require maintaining a slow drip of water to reduce the threat for freezing or bursting pipes, but a fail safe method is to drain the system and turn off the water at the source.
  • Cover, or Move Tender Plants Indoors. Cover with a light weight blanket or sheet and fasten in a tented fashion to prevent the wind from blowing the cover off. For in ground plants, water generously and provide additional mulch as insulation.

 

Keep posted to this website for the latest updates, as well as any Wind Chill, Freeze, and Winter Weather Watches, Warnings, and Advisories likely to be issued later in the week.

January 8th-10th 2010 freeze maker:  Arctic High pressure diving south from Canada and the Northern Plains (click to enlarge)

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