6:00 PM CST | December 22, 2018
Christmas Eve is just a couple days away now! Before long, 2018 will have come and gone. In the meantime, we have another system to watch. This one, which has been discussed for about two weeks now, will arrive just after Christmas. The weather models are advertising a strong system moving onshore the West Coast Monday. They track the core of this system through the Desert Southwest and into Colorado and New Mexico by Wednesday morning. Moisture will lift northward into the state in advance of this system. There are still some differences among the models which will have an impact on the forecast for mid-week.
If you have followed Texas Storm Watch for a while, you know that I like to wait until a system moves onshore before getting into specifics. Why? Because the most significant data available to the model guidance when a system is out at sea is satellite. Until a system moves into the US Upper Air Network, where weather balloons can actually "sample" the system, it is a "guestimate" of the system's strength.
Nevertheless, lows similar to the one being advertised have resulted in cool-season severe weather events. Just because it is December, severe weather can occur if the right ingredients come together. Right now, I expect at least an isolated severe risk for the state. I attached what this morning's GFS model shows at daybreak Wednesday and illustrated where the deep gulf moisture will reside at that time. This deeper moisture will lift northward during the day. Where the most favorable upper-level support overlaps the deeper moisture and instability is where severe storms are most likely to break out. Both the favored area and magnitude of the risk will be refined in the upcoming days. I would urge those living in, or traveling through, Texas and Oklahoma to keep an eye on the latest weather forecasts. Heavy rainfall will probably cause some localized flooding as well. Thereafter, we will switch gears back to winter as we end December and get into January. There will be an elevated risk for winter weather from the South Central Plains into the Ozarks and Mississippi Valley from the end of the month through at least the first week of January. That is all for this evening's discussion.
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