Lake effect snow is most common near the Great Lakes, but while rare in North Texas lake effect snow can happen in DFW and did happen overnight.
Why the lake effect snow in Texas? Water temperatures across most North Texas lakes are still in the 40s. Cold air moving over the warmer water causes warm air with moisture to rise. When the winds are at the appropriate direction and speed (winds can`t be too strong or too light and must have a long enough fetch over the water) the lift allows for clouds to form and eventually precipitation.
As a result, areas in North Texas south of area lakes received the most snow overnight. Generally, that was southern Dallas and Tarrant counties.
Some areas saw up to 2 inches of snow.
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Drier air moves into North Texas later Monday morning, ending the snow.
COLD WEATHER PREPARATION
Winterizing Your Home
Before the cold, replace worn weatherstripping on doors and windows to ensure there is a good seal. This will make sure warm air stays inside and cold air stays outside. Most modern windows are sealed inside the frame, but older windows may be sealed with a glaze that can crack and need replacing. The glaze may need to be applied above a certain temperature and it'll need time to cure -- this maintenance is ideally done in the spring or fall. Lastly, check your gutters to make sure they are clear and allow for water to flow freely to the downspout. Blocked gutters can lead to water entering the home. The Texas Department of Insurance also recommends trimming trees away from power lines, homes, and cars and checking the insulation level in attics.
Protecting Your Pipes
Most North Texans know to insulate their outdoor faucets, but if the cold snap is prolonged it could be a good idea to also leave inside faucets on external walls dripping overnight so that they don't freeze. The drip, drip, drip from running faucets, if heard, can be annoying, so put a sponge or towel in the sink to silently catch each drop. If you're leaving town for a few days, the Texas Department of Insurance recommends leaving cabinet doors open so that pipes on external walls are more exposed to heat. If you have pipes in an attic or crawlspace, are any other exposed pipes outdoors, they'll need insulation too. About those external faucets, disconnect hoses and insulate the valves. Wrapping valves with towels is not the best long-term solution. Most if not all North Texas hardware stores sell inexpensive exterior faucet covers made of foam that easily attach to the faucet bib in just a few seconds and do a great job protecting the pipe from freezing. If you suspect a pipe has frozen, keep the faucet open so that water can flow when it melts. Additionally, make sure you know where your main water valve is located (and how to turn it off) in the event a pipe bursts.
Bring in Your Pets
Even if you have a pet or animal that normally lives or sleeps outdoors, they could be susceptible to cold, hypothermia, and pneumonia. The SPCA of Texas says if you're cold outside, odds are your pet is cold too. Bring pets inside and make sure other outdoor animals have appropriate shelter, dry and well insulated, to protect them from frigid temperatures and possible death.
Protecting Your Plants
Perennial potted plants should be brought indoors. Plants that cannot be brought inside will need to be covered. Delicate plants can be covered with sheets, blankets, or landscaping frost blankets which can trap heat. During times of extreme cold, multiple frost blankets may be used. For plants left outside, a day or two before a freeze hits, the Dallas Arboretum recommends watering the soil only by hand only, keeping the foliage dry, to insulate the plant's roots. The Texas A&M AgriLife Extension has more here on how to protect plants from frosts and freezes. AgriLife also has tips on how to plant for the winter.
Turn Off Your Sprinkler System
You want to turn off your irrigation system for several reasons. One is that you don't want it running on its normal schedule, potentially throwing water on streets where it can freeze and be dangerous for passing cars. Second, you don't want to risk any broken pipes or valves that may come with a system that has not been winterized. To winterize your system, the city of Fort Worth recommends timers and back-flow devices both be turned off, even if you have freeze or rain sensors installed and that the main line be drained. Any pipes that are above the ground should also be insulated.
HVAC
Many air filters should be changed or cleaned every three months, or every season. But that's not the only winterizing needed for your HVAC system. You should have your ductwork checked regularly for holes (whether from vibration or rodents) to make sure the airflow is uninterrupted. If part of your HVAC is in the attic, it may also be home to rats, mice, and squirrels who find the warmth of the unit an ideal spot to build a nest.
Swimming Pools
Even if you have a freeze protector among your pool equipment, you'll want to look at the pump every day to make sure it's moving water through your pipes. Those pipes, too, can burst if they freeze.
Batteries
It's always a good idea to have a supply of fresh batteries in the event they're needed for flashlights during a power outage. If you didn't replace the batteries in your smoke and carbon monoxide detectors during daylight saving time -- now is a good time to make the switch. It's also a good idea to make sure your phone is charged so that you'll have access to timely information in the event of a power loss. Having a backup battery or power source to recharge your phone is also a good idea.