Severe Weather Possible This Saturday, April 26

Ingredients may come together to produce significant severe weather on Saturday across Texoma. There is some uncertainty with regards to the forecast so I do not want to hype the situation but do want to make all of you aware of the possibilities. 

First, a strong jet stream and upper level storm system will approach Texoma on Saturday afternoon as shown in these two images. 

Saturday evening jet stream forecast

500 mb level vorticity map

A vigorous upper level trough of low pressure will become negatively tilted with time which is favorable for producing sufficient lift to develop thunderstorms. The jet also acts to evacuate air from the updraft of thunderstorms and tilting the updraft which can promote stronger thunderstorms. 

*The timing of these features is critical to the development of storms and their strength. If it speeds up a bit or is in a favorable location during peak daytime heating, severe storms become more likely. If it is slower to approach, the severe threat would be lower and/or storms may not be as strong if capping in the atmosphere holds. Models do differ with this solution so we will be watching it closely over the next few days. 

Here are some severe weather parameters including the measure of instability which we call CAPE. This is anywhere between 1-3,000 J/kg depending on which forecast model you choose. This would be moderate levels of instability and enough to build and sustain storms. 

CAPE values valid Saturday evening

We also look at other parameters such as a supercell composite forecast which can help us determine where the greatest chance of rotating supercells are and to what degree the risk is. These values of between 4-10 are pretty significant so the primary type of storm would be supercells.

Supercell composite forecast valid Saturday evening.

Lastly, we will continue to track forecast soundings through this weekend since this helps to give us an idea how the atmosphere will look above our heads if parcels of air were released. It shows temperature, winds, and dewpoints and how a parcel would react if lifted in that particular atmosphere. This forecast sounding shows favorable winds shifting from SE at lower levels to SW at upper levels which can promote healthy, rotating updrafts. It also shows a slight lid on our atmosphere which may work to inhibit convection. However, I believe the jet stream energy will work to break this cap and we will get convection to initialize.

NAM forecast sounding valid Saturday evening for near Lawton, Oklahoma

Here's what you need to know...

Timing: 2PM-overnight. Tornado threat greatest from 4-9PM. Large hail & damaging wind threat possible anytime.

We will likely see a broken line of supercells develop just to the east of the dry-line then track northeast. Any stronger storms may turn east a bit more.

All of Texoma has a chance of seeing severe storms.

*Have a severe weather plan in place in case a storm heads towards your location. Stay with SkyWARN 7 weather for updates through this weekend. We will have extra hands in studio and I will be out storm chasing while streaming video.

A few links to help you out.

http://www.kswo.com/
My SkyWARN 7 Radar Online
My Facebook Page
National Weather Service Norman

First severe weather risk of 2014 for Texoma?

The month of March comes to an end Monday quietly but that may not last long as April kicks off Tuesday. 

A few key ingredients may come together Tuesday into Wednesday to give us our first chance of strong to severe thunderstorms. We've discussed the players before on tv but here is a very quick refresher on those ingredients. The Storm Prediction Center in Norman has already highlighted an area along and east of I-44 that is under the risk (Image 1).

Image 1

The 4 main ingredients to produce severe weather here in Texoma are moisture, instability, lift, and wind shear. 

We get our moisture from the Gulf of Mexico most of the time and by mid next week, forecast models are showing dewpoints in the 60s to 70s, (image 2) indicating plenty of moisture. Now, we will have to contend with the dry line which separates the moisture from very dry air and it will be close-by, so locations to the west of the dry line will not be in a favorable environment for storms. Right now, the best call would be for that dry line to setup between Altus & Lawton but things may change. Another ingredient is lift which usually comes from developing areas of low pressure, fronts, or disturbances in the jet stream. A serious of what we call shortwave troughs will approach the Southern Plains starting on Monday. The first wave is weaker and stays to our north mostly. A second, stronger wave approaches by Wednesday into Thursday and this may be the trigger needed to produce thunderstorms. (Image 3). We can measure how much lift we have by looking at the lifted index. (image 2).

Image 2 (lifted index & dewpoints)

Image 3

What about instability? We can measure instability in a few ways and one of them is by looking at what is called convective available potential energy (CAPE). I won't get into how exactly we calculate CAPE but just know that we can look at forecast CAPE values on various forecast models. CAPE values increase quite a bit, especially by Wednesday, with values exceeding 2,000 J/kg in the black boxed in area (image 4). This is more than sufficient to support the development of thunderstorms.

Image 4 (CAPE forecast)

Lastly, we need wind shear. What is wind shear? We are most interested in vertical wind shear which is how speed and/or direction of the wind change with height. In the case of mid next week, we do have wind directions changing with height and we have speeds increasing with height. Both of these factors can promote a strong updraft in thunderstorms. (image 4).

Image 4, Wednesday evening GFS forecast sounding

So after going over all of these ingredients you must be saying "wow, we are going to get bad storms!". Well, hold on just a second. It is hard to get all these ingredients to come together in the right mixture at the right time to produce severe weather. Is there a possibility of severe storms in Texoma by mid next week? Sure, but we have several days to watch trends and changes in our forecast models to better fine tune the forecast. This is just an early heads up and a nice refresher to get yourself acquainted with terms we may use throughout this Spring storm season. Be sure to stay with SkyWARN 7 weather over the next few days, we will keep you updated! 

Much Needed Soaker for Texoma.

Liquid gold fell out of the skies during the weekend of March 15-16th.

After a long winter of cold temperatures and several ice/snowstorms, we were thankful for the precipitation but most were sick of it. Unfortunately, precipitation during the month of February really came up short with Lawton picking up 0.09" (-1.25") and Wichita Falls receiving 0.35" (-1.40"). Well, March came through with a great soaking in parts of Texoma minus the ice and snow. Locations along and east of I-44 did quite well with some areas topping 2" but areas to the west missed out on the heaviest rain and by the looks of the drought monitor, those locations need the rain the most.

Here are the 48 hour rain totals across the region:

*Note: Wichita Falls received 1.84" on March 15th which was a daily record. The old record for the date was 1.55", set back in 1998!

Below is the drought monitor (updated last Thursday) which shows exceptional drought spreading in Texoma, especially western North Texas and far western Oklahoma. Although, there was some rain in these locations, it will not be enough to make big improvements. The next update to the drought monitor is scheduled for Thursday and we may see some improvement in eastern Texoma.

Our next chance of rain may arrive as soon as this Saturday, March 22nd or as late as around the 24th. So far this month, we are at 1.93" of rain in Wichita Falls which is around 0.30" below average compared to the average monthly total and we still have around 2 weeks to go before the month ends so that is some good news. Here in Lawton, we are at 0.62" which is about 1.70" below average for the whole month but again, we still have time to make up the deficit.

Have a fantastic week and remember, you can always head to www.kswo.com for your full SkyWARN 7 video forecast and the latest 7 day.