Day 25: The Upcoming Southern Plains Winter Storm
The upcoming winter storm (identified on yesterday’s post) is certainly what everyone is talking about in Norman. In fact, at today’s Hazardous Weather Testbed (HWT) Map Discussion there were over 40 people in attendance – all focused on what would unfold later this week. Tonight I thought I would take a look at what the Hydrometeorological Prediction Center (HPC) is currently forecasting.
Above is the current 5-day HPC precipitation forecast. Almost all of the precipitation across the southern plains is associated with the shortwave trough forecast to affect the area Wednesday night into Friday morning, aka the potential Winter Storm. Ultimately, the big question is what will the precipitation type of that amount be. As a rule of thumb (and a starting point), 1″ of liquid is approximately 10″ of snow – however, a lot of things can affect that ratio.
Using the 10:1 ratio above, if all of the precipitation were to fall as snow, a good portion of the southern plains would be buried under almost 2 feet of snow. The good news for Oklahomans and Arkansans is that all of this precipitation is not forecast to fall as snow. So what then are meteorologists currently forecasting? The next few images should help break that down as best as meteorologists can currently forecast. It should be pointed out that the forecasts below are valid from 00Z Thursday (6PM CST Wednesday) until 00Z Friday (6PM CST Thursday), whereas the precipitation forecast above is valid through 00Z Sunday (6PM CST Saturday). Thus, additional precipitation will fall after 00Z Friday (6PM CST Thursday) and most of that will fall in the form of some wintry precipitation.
Above is the probability of an area receiving at least 4″ of snow. As you can see, HPC forecasters have greater than 70% confidence that a large portion of northwest Oklahoma, northern Texas Panhandle, and southern Kansas will receive at least 4″ of snow.
Above is the probability of an area receiving at least 8″ of snow. Again, HPC forecasts have fairly high confidence that a good potion of the northern Texas Panhandle and northwest Oklahoma will receive over 8″ of snow.
Above is the probability of an area receiving at least 12″ of snow. It isn’t too often you see confidence high enough to warrant a 70% area for at least a foot of snow this far into the future for a southern plains winter storm. However, a large swath of 40% probabilities is nothing to sneeze at! Remember, more snow will fall in parts of that outlooked area after the end of that time period!
And last, but not least, what about areas to the south and east of the heavy snow? What does all that precipitation fall as? Unfortunately, it appears that there is enough confidence to warrent a 40% probability that some areas will receive at least 0.25 inches of freezing rain. This is the criterion for what is known as an Ice Storm. Couple this much freezing rain with the expected strong winds, some places will most likely see power outages.
Editor’s note: While I was writing this data from the latest (00Z, 6PM CST) run of the North American Model (NAM) began to come in. This run is considerably slower and stronger than previous runs. It holds off most of the heaviest winter precipitation until after 00Z Thursday (6PM Wednesday). In fact, between 1.5 and 2 inches of liquid equivalent is forecast in the cold sector of the storm Thursday night. The model forecasts this to fall as heavy, wet snow along the I44 corridor in Oklahoma. This would easily result in over 12″ of snow in this portion of Oklahoma – again – if this model run turns out to be true. A lot can (and will) change over the next few days. Don’t get caught up in the details of a single run, just know that there is the potential for a major winter storm late this week!
