Severe Thunderstorm Warning for Johnson County in North Texas until 5 PM. Severe thunderstorms are entering the western part of the county from Cresson to Godley to west of Bono. These storms are moving northeast at 30 MPH and will impact much of Johnson county through 5 PM. Quarter size hail and wind gusts of 60 to 70 MPH are possible with the strongest storms. Cleburne, Joshua, Alvarado, Rio Vista, and Grandview are all included.
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE FORT WORTH TX
354 PM CDT THU OCT 2 2014
THE NATIONAL WEATHER SERVICE IN FORT WORTH HAS ISSUED A
* SEVERE THUNDERSTORM WARNING FOR…
JOHNSON COUNTY IN NORTH CENTRAL TEXAS…
* UNTIL 500 PM CDT
* AT 354 PM CDT…NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL…AND
DAMAGING WINDS IN EXCESS OF 65 MPH. THIS STORM WAS LOCATED NEAR
GODLEY…MOVING NORTHEAST AT 30 MPH.
* THE SEVERE THUNDERSTORM WILL BE NEAR…
CLEBURNE AROUND 400 PM…
JOSHUA AND KEENE AROUND 410 PM…
BURLESON AND GRANDVIEW AROUND 420 PM…
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.
1045AM: Isolated Storms across Western North Texas
A couple showers and thunderstorms have developed west of the D/FW Metroplex over the past 30 minutes. Extending from Alvord and Decatur south to Cresson this activity is quickly moving north/northeast at 45 to 50 MPH. This convection is a sign of increasing upper level lift across North Texas as a strong upper level disturbance and cold front begin to enter the region. As of 10:45 AM this activity is not severe and the strongest cores are producing brief heavy rain and cloud to ground lightning. One or two storms may become strong to marginally severe through lunch-time.
After 1 PM focus will begin to shift to the approaching cold front as instability levels increase across North Texas. Initial thunderstorm development is expected between 1 and 3 PM just west of I-35. These storms could become strong to severe with large hail and damaging winds. Storm coverage will increase as they move through the I-35 corridor. A near solid line of thunderstorms is expected by the time storms move east of I-35. I’ll have a more detailed update on this afternoon and evening’s storm chances after 11:30 AM.
A strong upper level storm system along with a southward advancing cold front will slam into a strongly unstable, humid air mass on Thursday across North, Central, and East Texas. A severe weather event is anticipated tomorrow as a line of thunderstorms should develop along an advancing cold front by the mid-afternoon hours. Ingredients will be in place to support the risk of severe thunderstorms capable of producing damaging wind gusts and large hail. The Storm Prediction Center has placed portions of Northeast and East Texas in an enhanced risk of severe weather tomorrow running along and east of US-75 from Sherman to Dallas and north of Interstate 20 from Mesquite to Marshall. A larger area of severe weather risk includes much of North and Central Texas into the Hill Country along with the Brazos Valley and East Texas. Ingredients are coming together for the possibility of a severe weather outbreak with a line of severe thunderstorms.
An upper level jet will dip south into Texas by the late morning and early afternoon hours tomorrow. By the mid-afternoon this upper level jet should be favorably positioned in conjunction with an advancing cold front. Winds at 500 millibars or about 18,500 feet above sea level will be exceeding 45-55 knots. The minimum wind speed I like to see for more organized thunderstorms is 35-40 knots at 500 millibars so the upper level winds will support an organized convective mode. The reason we look for stronger winds in the upper atmosphere is that the winds will help blow precipitation away from a thunderstorm’s updraft thus allowing warm, unstable air to continue feeding into it. When upper level winds are weak precipitation has a tendency to fall straight down or into the updraft. When precipitation falls back into the updraft the warm/unstable air is cut off and the thunderstorm weakens. During the summer months we refer to those storms as popcorn storms since they go up quickly, produce a light of lightning and heavy rain, but quickly weaken and usually dissipate within 30-45 minutes often resulting in a localized microburst. Since winds tomorrow in the upper levels of the atmosphere should blow rain out of the updrafts we expected a more organized convective mode and longer lived storms.
If you’ve been outside today you know temperatures are quite hot and muggy. Temperatures are well above average across North Texas today and will be again tomorrow as surface temperatures climb into the lower 90s. One way to measure moisture in the atmosphere is the dewpoint temperature. The dew points this afternoon across the eastern half of Texas are in the 50s, 60s, and even 70s. Honestly today feels like an April or May afternoon which is usually not a good thing when you’re talking about a upcoming storm system in early October. With a very moist atmosphere in place ahead of the cold front tomorrow the atmosphere is going to become strongly unstable. Surface based convective available potential energy (CAPE) values will exceed 2,000 to 3,000 J/Kg by the afternoon hours Thursday. Those are fairly impressive values for October and in combination with the strong upper level dynamics and cold front could support an appreciable severe weather threat.
One unknown factor that is still causing some uncertainty is the actual placement of the cold front when thunderstorms begin developing Thursday afternoon. Some model solutions have thunderstorms developing east of I-35 and keeping the D/FW Metroplex and everyone west of I-35 will remain dry. Other models suggest thunderstorms will begin developing along a Nocona-Mineral Wells-LaLampasasine. The first storms will begin developing across Oklahoma and gradually build south along the cold front. Thus the first storms will develop near the Red River and build south into Texas as the cold front moves east. Hence where the cold front ends up when storms fire will determine exactly where the rain chances begin. Based on current data and the National Weather Service Fort Worth’s thinking the current forecast shows thunderstorms developing just west of the D/FW Metroplex and I-35/I-35W by the mid afternoon hours. Thunderstorm cocoverageill increase as the cold front/squall line moves into D/FW with a nearly solid line of storms by the time they end up east of D/FW and US-75/I-45 in the enhanced risk zone. This could chance and storms could fire further west or east and radically chance the overall storm chances for the D/FW Metroplex.
Due to the combination of favorable ingredients for severe weather once storms get going they will likely become strong to severe quickly with a threat for damaging straight line winds exceeding 60 MPH and hail up to the size of golfballs. Not everyone will be hit by thunderstorms tomorrow. Not everyone who gets a storm tomorrow will receive large hail or damaging winds. The overall setup favors a linear event (squall line) with low level wind shear unidirectional and marginal. The tornado threat will be low but not zero. Any individual thunderstorms that manage to stay by themselves for a while or interact with an outflow boundary could produce hail up to the size of hen eggs and exhibit some rotation. While weak low level winds will keep any tornado threat localized and marginal any supercell storms will have to be watched.
Saturday’s Weather Roundup – Cold Front pushing through North Texas
Good morning and happy Saturday! A weak and shallow cold front is currently pushing through north Texas and into the DFW metro area. It will continue to slowly drift south during the day today, eventually stalling and phasing out in the Waco vicinity. Behind the front, temps are currently in the 50 to 60 degree range across the panhandle and south rolling plains. Highs out there today will remain cool due to extensive cloud cover that is expected to keep the area socked in until tomorrow. Here’s a look at the current radar image showing a broad area of rain continuing to impact parts of the south rolling plains and up into western north Texas around Wichita Falls, Vernon and then further south towards Snyder.
Best chances of rain today will be across western north Texas this morning, then shifting south between DFW and Waco and over into west central Texas by later this afternoon. Scattered showers are also expected once again along the coast as a little disturbance travels southwestward over the area. Overall very similar to what’s been experienced the past couple of days. Some of these showers could become strong with gust winds and frequent lightning. Can’t rule out an isolated funnel cloud or two with the amount of moisture still impacting the region. Across far west Texas, best chances for seeing heavy rain will occur later this afternoon then into the overnight hours, then again on Sunday. Flash Flood Watches have been posted for a majority of the west Texas counties and include the cities of El Paso, Pecos, Ft. Davis, Marfa and Presidio.
Highs today will obviously be impacted by both the front and any showers/storms. Overall though, not too bad with the highest readings average in the mid 90’s across the southern half of the state. Nighttime lows will be quite cool across western Texas, the panhandle and western north Texas. We’ll start to warm up again by Monday, but we are still on track to receive a much stronger cold front by the end of this next week, so hang in there!