Weather Talk: Sunday’s storm potential

Weather Talk: Sunday’s storm potential
MGN Online
Weather Talk

POSTED: Saturday, April 12, 2014 - 9:33pm

UPDATED: Tuesday, April 15, 2014 - 11:52am

Monday 12:15AM Update:

Severe T-Storm Watch until 6AM Monday morning for the following counties: Camp, Cass, Franklin, Gregg, Harrison, Henderson, Hopkins, Marion, Morris, Rains, Smith, Titus, Upshur, and Van Zandt.

Showers and storms will move from the NW to the SE through the overnight hours. Not everyone will see rain, but this will be along the cold front approaching the area. Behind the front, much cooler air.

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Sunday 8:45PM Update:

Good evening everyone. I have a few updates for you.

1. Tornado Watch remains in effect until 12AM tonight for most of East Texas. Why? Because an intense line of showers and storms are crossing the Red River and headed toward portions of East Texas. You can see the Severe T-Storm Warning boxes for this line (see image). I am hoping this line weakens as it comes toward us, but it is packing a strong punch. This line is the Cold Front. Behind it, very gusty northwest winds.

So, for the next few hours, we will remain quiet in East Texas. Storms will enter our northern areas after 10PM. KETK Meteorologists are expecting the line of storms to enter Tyler/Longview after midnight.

2. I have had multiple reports of possible damage caused by a tornado or straight line winds in Camp county and Houston county. I have been in contact with the NWS offices and we are looking to see if there have been additional reports. If you have any photos or videos, please send them to newsroom@ketknbc.com.

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Sunday 6PM Update:

Tornado Watch issued for a good portion of the viewing area. Counties included in the watch: Anderson, Camp, Cass, Cherokee, Franklin, Gregg, Harrison, Henderson, Marion, Morris, Panola, Rains, Rusk, Shelby, Smith, Titus, Upshur, Van Zandt, & Wood. This watch is in effect until 12AM tonight. Scattered strong storms will be possible through thie evening and into the early overnight hours.

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SUNDAY 2PM Update:

This afternoon, we are seeing a line of showers and storms moving into East Texas this afternoon. This is providing a lot of lightning and heavy rainfall. This activity is moving East/Northeast.

We will get a break in the shower and storm activity in the next few hours. Our focus then turns toward the dryline where showers and storms are already initiating.

The High Resolution Rapid Refresh (HRRR) model is showing some showers and storms racing toward East Texas by late this evening. While forecast models do not fully depict what will actually happen, it gives a good idea of what the environment is like. With that being said, we will need to keep a close watch of what develops to our West.

Here is the HRRR output of storms this afternoon and evening.

The KETK Weather Team will be watching these storms closely.

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Saturday 10PM Update:

The risk of strong storms on Sunday is present, and there will be two possibilities for this to happen. In this post, I will detail the overall setup, talk about each possibility, and give an overall forecast of what you can expect for Sunday.

THE SETUP

There are three factors that will cause storm development.

First, the upper level forcing will be present to aid any surface-based storms to fire up over our area. The GFS model shows the increasing positive vorticity, allowing storms to form and grow.

The second factor that can lead to storm support since upper-level forcing is present is the dryline. If you recall, the dryline separates the hot/dry air (west) from the warm/moist air (east), and measured by dew point values. As the forcing moves overhead, the dryline will slide eastward, and this could aid in the storms to form along the dryline. The maps below show the progression of the dryline from 7AM to 1PM to 7PM on Sunday.

The final factor is a very strong cold front being forced into the Central Plains and headed for East Texas late Sunday night.

These factors, along with a very strong southerly wind flow will set us up for storms. Now, will they happen? Let’s talk about that.

STORM POSSIBILITY #1—Afternoon & Evening

Sunday afternoon and evening storms will be initiated by two mechanisms—the upper-level forcing and the dryline. The limiting factor with these storms will be the CAP—a layer of warmer air aloft which limits or delays thunderstorm potential. The GFS model has the CAP breaking by the afternoon hours and the NAM keeps the CAP for much of the day.

Right now, I believe that storms will be likely to initiate along the dryline by the early afternoon and will move into East Texas by the late afternoon and evening hours. If we have more sunshine and can destabilize the atmosphere more, then storms will become more likely. This is also why KETK Meteorologists are keeping our storm percentage at 40% on Sunday is due to uncertainties with the system.

Here is the RPM model of storm development in the afternoon.

If this model does verify with the storms, then they will be able to contain damaging winds, large hail, and the threat of a tornado. These types of storms will be supercells—meaning they contain very heavy rain and very strong winds feeding the storm and moving it. These storms look to continue in the evening hours. Remember, we will need the CAP to weaken and instability to rise if these storms are to develop—and we will be monitoring this carefully on Sunday.

STORM POSSIBILITY #2—Late Evening & Overnight

This second possibility will initiate as a cold front moves into our area. This round will look more likely to occur late Sunday night and into Monday morning. The chance of severe weather is less during this time period, but some damaging winds are quite possible as this cold front passes through.

The RPM model is not showing a lot of precipitation, but I do believe that the showers and storms you see in SE Oklahoma and into SW Arkansas will be aiming for East Texas in the overnight.

The shower and storm activity lingers around until Monday afternoon, at the latest, and then we will see skies clear out. Monday will be very windy and much cooler with falling temperatures during the day. Monday night = VERY COLD. Overnight lows will be in the low to middle 30s and frost will be likely as well.

FORECAST

By Sunday morning, there will be a few areas of light rain. Overall coverage is about 10%-20% of the area. The main focus for severe weather on Sunday will be in the state of Oklahoma. Here in East Texas, I believe that we will see some strong to severe storms become likely by Sunday afternoon and evening. The greatest threat with these storms will be large hail and damaging winds. The tornado threat does exist, but it is not as significant as the other two factors.

The key factors our KETK Weather Team will need to watch for on Sunday are: the CAP breaking, more sunshine, where the storms will initiate. These factors will be determined as newer model data comes to us and what happens during the morning hours on Sunday.

You will want to be weather aware on Sunday and know your plan of safety before severe weather strikes. Our entire KETK Weather Team will keep you up to date. Stay tuned to KETK-TV, our KETK Facebook Page, our KETK Twitter Account, and our KETK Mobile App. For the weather forecast, visit our weather page.

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