We’ve already had two fatalities in Texas this year and we’re only into the second week of March. Severe weather is hardly rare during the first months of the year, but we do start to keep an eye on trends as we approach early spring. Trying to forecast specific weather parameters is challenging three to four days out. Attempting to nail down a general weather pattern one to two weeks in advance is just as difficult. Looking at the longer-range means we’re not looking for specifics but a general trend or agreement among weather models. A pattern change is one example where longer-range data can actually be useful. Without trying to pin down specifics, but having increased (or decreased) confidence in a general weather pattern helps to guide a forecast as it grows closer in time.
Various weather models and their ensembles are showing a potential pattern change as we get into the upcoming weekend. An upper-level storm system (or trough) should be in place across the Southwest United States, perhaps over California. Depending on how long that system sits before ejecting east is one question. Another question is how strong with that upper-level storm system be when it approaches the southern United States. Just to make this equation more complicated – one also has to consider more subtle impulses (or “lift” in the atmosphere). We’re not trying to get those questions answered just yet, but we are keeping an eye on general trends in the weather model guidance. So far models have an idea of a pattern change – but digress on specifics.
We’ll have to wait and see how things line up. Dewpoint temperatures this evening in Texas range from 14 degrees in Amarillo to 50 degrees in Brownsville with northerly winds. A cold front has pushed the higher moisture values well out into the Gulf of Mexico. It takes several days of southerly/southeasterly winds to bring all that moisture back inland. When forecasting precipitation chances that is one key ingredient. If enough moisture was in place ahead of this weekend’s storm system we could see a higher chance of thunderstorms. With a surface dryline expected (although the exact placement can’t be determined yet), we would see a sharp gradient between hot/dry and more humid air masses. Those who have lived in Texas know the dryline is the main player in spring-time thunderstorms. We will have to keep an eye on data as we get closer to the weekend regarding any thunderstorm chances. A second concern is a very dry airmass in place west of the dryline. When that upper-level storm system gets closer we could see fairly strong westerly/southwesterly winds west of the dryline. Low humidity, very warm temperatures, strong winds, and a severe drought all mean trouble for firefighters.
Could this weekend end up being my first storm chase of 2018? Maybe, but it could just as easily be capped east of the dryline (meaning no storms). Hopefully, we can get some precipitation chances to areas that need it, but don’t get your hopes up yet. We’re still in the range of “voodoo” on weather models. One run can look completely different than the last. Just keep an eye on the forecast for the end of the work week and into the weekend.