Category 4 Severe Risk Today
The spring severe weather season is not any breaks. The Southern Plains are under the gun again for severe thunderstorms this afternoon and evening. The Storm Prediction Center upgraded the thunderstorm outlook, which includes a moderate risk for southwestern Oklahoma and northwestern Texas. There is an enhanced risk surrounding this moderate risk, which includes the OKC Metro and locations just west of the DFW Metroplex.
Today’s Severe Thunderstorm Outlook (SPC)
A moderate risk is considered a category 4 risk on a scale of 1-5 (with five being the most significant). By SPC definition, a category 4 risk means this area has a likely chance of widespread severe weather with several tornadoes and/or numerous severe thunderstorms.
Severe Thunderstorm Risk Categories (SPC)
Taking a look at the latest observations across the Southern Plains, currently a surface low is located across southeastern New Mexico/far western Texas, with a warm front extending across southern portions of northern Texas. To the south of this warm front, rich moisture has returned and is advecting northward. Dewpoints are currently in the mid 60s-close to 70 south of the warm front. This front will continue its northward progress and likely lie across the Red River Valley this afternoon.
The position of the warm front is important in today’s severe potential because the warm front can serve as a boundary for enhanced tornado risks where enhanced Storm Relative Helicity value swill exists. The SRH in the vicinity of the warm front should exceed 100-250m^2/s^2. Recent literature shows SRH values, which is basically a measure of potential rotation, larger than 100m^2/s^2 increases the tornado threat. The warm front should be near the Red River during the early afternoon, once some daytime heating has occurred, so this area may see a couple supercells develop across north Texas/southern Oklahoma during the afternoon hours.
The current satellite imagery indicates skies are obscured in many areas, but sunshine should partially ensue. This coupled with the low-level moisture, will allow CAPE values (ML) to exceed 2000-3000 J/kg. This means there will be adequate “food” for the storms.
2m Dewpoint HRRR Forecast This Afternoon (Pivotal Weather)
Mixed Layer CAPE HRRR Forecast This Afternoon (Pivotal Weather)
A storm or two could erupt along the warm front (north Texas/southern Oklahoma) around 4:00PM or later today, and thunderstorms also develop along the dryline around 4:00PM in western Texas. With time, as the storm system traverses eastward, the discrete mode of thunderstorms should transition into a linear mode. A large squall line should impact much of Oklahoma and Texas overnight. The main threats during the late evening and overnight will transition from tornadoes and very large hail, to damaging winds, hail, and isolated flash flooding. It should be noted, the severe threat (primarily damaging winds and hail) will continue well into the overnight hours.
HRRR Forecast Radar This Afternoon (Pivotal Weather)
HRRR Forecast Radar Overnight (Pivotal Weather)
Again, all modes of severe weather are possible this afternoon. This includes very large hail, tornadoes, and wind. Initially, between 4:00PM and 8:00PM, very large hail (tennis ball to baseball size) and tornadoes are most likely for southwestern Oklahoma and northwestern Texas–and whatever storm develops across the Red River Valley. Then, the threat should transition to an isolated tornado and hail threat with more on an emphasis on wind damage due to the evolution of a squall line.
SPC Tornado Probability Map
SPC Hail Probability Map
SPC Wind Probability Map
This forecast is not intended to create hype or worry you. I am simply implying the severe threat is real today if all the parameters come together as the short-range numerical guidance is indicating. Do not panic, just have a plan in place. Tune in to your local television station so you’re notified of warnings, call your elderly neighbors to make sure they have a plan, and know where you will shelter in case a warning is issued for you area. This is nothing unusual for this time of the year in the Southern Plains.