10:30 PM CDT | March 26, 2018
Could we see a chilly start to April? Yes, it is certainly possible. As we have discussed over the last several weeks, the weather pattern will be favorable for colder air to push into the Southern Plains through the first week of April. Most of you are familiar with the recurring cycle theory. If you are not familiar with it, feel free to visit the About page for more information. In a nutshell, it holds that a unique weather pattern sets up in the fall. Once it finishes setting up, the weather pattern begins repeating or "cycling". In past years, the cycle length has been anywhere from 40 to 65 days. This time, it has been cycling between 46 and 51 days. The same features (ridges, troughs, etc.) come into play with each cycle, but the strength and location can differ depending on the seasons and other factors. It gives you an idea of when to watch for active weather. It is a really cool theory that was first discovered by a Kansas City Meteorologist back in the 1990's.
Okay, now let's get to the topic at hand. The part of our weather pattern that has previously brought colder air and wetter weather to the region since fall has cycled around again. Texas will see some much-needed rainfall over the next few days. Behind the cool front and where this heavier rain is occurring, temperatures will dip below seasonal norms during this time. Temperatures will rebound by late this week, but more changes should arrive the first week of April. The part of our weather pattern that will cycle during the first week of April is what brought the big cold snap to Texas on/around New Year's. If you are new to this theory, it may sound far-fetched. Let me show you what we saw back then, and what the weather models are starting to show - two cycles later.
Courtesy of the SFSU weather page, This is the 500mb pattern from December 29, 2017 to January 3, 2018. You can see a large trough organize over the Midwestern US and Canada with pieces of upper-level energy digging into the Southern United States, east of the Rockies. This allows cold air to spill southward into the region.
This becomes very evident when looking at the surface conditions. The following video shows the surface pressure and observations in 12-hour increments (6 AM and 6 PM) from December 29, 2017 to January 3, 2018. Notice the surface high in Western Canada at the start? Watch how it builds southeast into the Ozarks a few days later. This is the core of that cold shifting into the Central United States.
This is a look at this morning's European model, courtesy of the Penn State Meteorology Department. In the top left corner, you can see a large trough over the same area at the start of the video, Easter morning. A piece of energy pivots around the base of the trough and into the Eastern US by April 3rd. Look at the top right, you can see the surface high near the US/Canadian border shift south and east. While not shown here, this morning's European model had temperatures in the 30*F's across the northwest half of the state by the morning of April 2nd with hard freezes across the Texas Panhandle. Quite a cold snap!
This morning's Canadian model showed a similar scenario but a bit slower and colder than the European. By the morning of April 3rd, it shows freezes for the northwest third of the state with 30*F's into North Central/West Central Texas. Meanwhile, the GFS (American) model was both earlier and MUCH warmer with the front. On Easter morning, it had temperatures in the 30*F's across the Texas Panhandle with warmer temperatures to the south and east. The European and Canadian solutions align with the recurring cycle theory, whereas the American model does not. It will be interesting to see how things unfold several days from now. The expected weather pattern makes the colder scenarios possible but not a certainty at this time. It is why I still believe that at least the northern half of the state is not yet in the clear for frosts and freezes. You can get the latest here on the blog and Facebook page.