It’s an unbelievably muggy afternoon across the eastern half of Texas with dewpoint values in the 70s to almost an unheard of 80 degrees in South Texas. This is the kind of atmosphere we see during June and July with summer heat.. not during October! That should help emphasis the type of atmosphere we have in place today. With such impressive moisture in place the atmosphere is almost like a powder keg and is very unstable. That’s part of the reason were going to have such a large area under the gun today and tonight as a strong cold front moves into Texas. Enough about moisture content lets get down to business and look over the new severe weather outlook.
The new severe weather outlook released at 11:30 AM does not contain and major changes. For the purpose of defining each severe weather hazard I’ve divided the graphics into a hail risk and a damaging wind risk. The risk for large hail will be highest when thunderstorms first develop this afternoon and for the first few hours of the event. The overall risk for damaging winds will increase as storms congeal into a squall line. That’s why you’ll see some discrepancy between the highest risk areas for hail and damaging winds. Starting off with the outlook for large hail we have an enhanced risk for much of North and Northeast Texas. This includes the D/FW Metroplex, Hillsboro, Sherman, Paris, and Canton. Severe storms containing large hail will be possible across Central and East Texas as well.
The risk for damaging winds is enhanced across Northeast and East Texas including Sherman, Dallas, Athens, Tyler, Longview, Paris, Mt. Pleasant, and Texarkana. Severe thunderstorms containing large hail and damaging winds will be possible across much of Central Texas, the Brazos Valley, Southeast Texas, and Deep East Texas. Waco, Killeen, Austin, College Station, Lufkin, and Jasper are all in a severe weather risk today. While not included at this time the latest high-resolution model data does suggest the severe weather risk may need to be expanded to include Southeast Texas and the Houston Metro as the squall line may continue there late tonight.
The timing for today’s severe weather hasn’t changed much from our earlier thinking. There have been a few showers and thunderstorms across western North Texas this morning. While they have not been severe they did give some locations brief heavy rain and a few loud claps of thunder. What interests me about those showers/storms is that they may have produced outflow boundaries. As we head into the afternoon hours these outflow boundaries could locally enhance low level wind shear. I only mention this because we’ve had this happen before during a squall line event. The High Resolution Rapid Refresh (HRRR) weather model suggests we may have a few discrete thunderstorms form by 1-2 PM across the D/FW Metroplex just ahead of what will become a squall line. With an unstable airmass in place any discrete thunderstorm that becomes supercellular will need to be watched closely for low level rotation. Any discrete supercell that interacts with an outflow boundary could have the ability to produce low level rotation and possibly even a tornado. This isn’t to say we’re going to have issues with tornadic supercells today, but there is a small chance the initial discrete storms could interact with an outflow boundary and give it a shot in North Texas.
ANIMATION: 12 PM through Late Tonight
The first thunderstorms along the cold front should begin to fire by 2-3 PM. There remains some uncertainty exactly on where the storms will fire but all indications are it will be just west of the D/FW Metroplex. That means storms will be maturing and likely strong/severe as they move through the I-35 corridor in D/FW. By the time they exit D/FW and move into East Texas there should be a mature squall line. The primary severe weather hazards with initial discrete storms will be large hail up to the size of golfballs, damaging wind gusts up to 65 MPH, and possibly an isolated tornado as I described above. Once storms congeal into a squall line the primary hazards will be damaging wind gusts up to and possibly exceeding 70 MPH and hail up to the size of quarters and possibly golf balls. Low level winds will be unidirectional and not particularly favorable for tornadic development. However I can’t rule out a brief spinup with embedded supercells or complex structures in the squall line.
I expect we’ll see our first severe weather watches by 2 or 3 PM across North Texas with additional watches across Central and East Texas later this afternoon and into tonight. Please remember to keep an eye to the sky and check back for updates this afternoon.