Earlier this week we posted the graphic below regarding the severe weather possible for tomorrow afternoon/evening. Our thinking has not altered much since we created this. However, there are a few variables that could sway the weather tomorrow, so pay close attention throughout this blog as this system seems to be fairly complex. We are going to try and give you the best timing and placement for tomorrow to help aid you plan ahead properly.
- A strong area of low pressure to our northwest will began its progression east throughout the next couple of days. This is the culprit to the powerful storm system set to bring severe weather and heavy snowfall for a large portion of the United States over the next few days.
- Scattered rain showers will develop tomorrow morning and continue throughout most of the day. These showers could have a few embedded thunderstorms, but should remain under severe limits for the most part.
- These pre-frontal showers could help aid in stabilizing the atmosphere tomorrow, lowering the overall severe threat. We are crossing our fingers for this, if we had sunny skies throughout the day this entire event would be a whole different story (big tornadoes).
- There could be some severe development during the mid-afternoon, but we are confident that most severe weather shouldn't initiate until the evening hours (after 5 PM). This is great, especially regarding the school hours for children.
- Tomorrow evening as the dry line approaches western Arkansas a very unstable warm sector will began to track east sparking strong thunderstorms - some severe and possible supercelluar.
- Models have went back and forth on where exactly these storms will begin to fire, and we may not know this until it actually gets here. This is the reason we highlighted the entire western section of Arkansas in red.
- Some of us may NOT see any severe weather at all. Remember that statement, as we have stated these stronger storms could be isolated rather than a large line of storms like we usually see. Especially across far western Arkansas as this will be a developmental zone for thunderstorms.
- Eventually, thunderstorms will form into a large complex and track east, finally exiting the state to the east early Saturday morning. This is a good thing, as this will help lower the tornado threat.
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| Unstable atmosphere tomorrow evening |
We have included the surface based CAPE model above, to help better explain the reason for the stronger thunderstorms. CAPE is basically the fuel needed for thunderstorm development. As you can see, the western half of Arkansas will have a plentiful amount of energy to work with for storm development tomorrow evening. We've included an arrow on the right side of the graphic pointing to the scale reading. Notice there are areas exceeding 3,300 J k/g, which is more than enough instability for stronger storm development. This energy does die off some as the system progresses east, thus our reason for leaving eastern Arkansas at lower chances for more widespread severe weather.
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| Our target area for isolated tornadoes |
After looking over model data for the last couple of days, and this morning, we have included a graphic above for our target area for isolated tornadoes. This does NOT mean other places will not see any tornadoes, or severe weather for that matter. However, we feel this highlighted area has the best chances due to supercell composites and helicity values. The circled area above will need to be watched very close during the afternoon/evening hours tomorrow until the threat has moved east.
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| Simulated radar example of isolated thunderstorm development |
Tomorrow evening there will likely be a large complex of thunderstorm moving east. This is to be expected, and these storms could hold some severe potential of it's own. However, our main focal point will be isolated cell development on the backside of the large complex. We have circled an example in the above posted model data. These individual cells will hold a higher tornado threat and could become supercelluar as they initiate along the dry line in the unstable air mass (explained above). Until these storms form into a larger complex we will need to be on a higher alert for tornadoes due the isolated nature of the cells.
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| Supercell composite for tomorrow evening |
Supercell composites are not off the charts for tomorrow, but there is certainly plenty of energy to work with. We like using composites because we can fit a large amount of information into one model itself, helping better explain the situation at hand. We didn't post this in hopes of scaring anyone, but rather it help show you the environment will be amplified tomorrow evening. Notice the higher values across southwest Arkansas (our target area).
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| Storm Prediction Center outlook for tomorrow (Friday, April 13th) |
Lastly, we leave you with the Storm Prediction Center outlook for tomorrow (April 13th). A large majority of Arkansas is currently under an enhanced risk of severe weather. There could be an upgrade to a moderate risk (level 4) by tomorrow, likely for western, and southwest Arkansas. Remember, just because your area is not at risk for stronger tornadoes does not mean you could not experience severe weather. Eastern Arkansas is included in this graphic due to the nature of the storms as they move east. These storms could hold a damaging hail, and damaging wind threat.
Key points in conclusion:
- Rainy day Friday regardless of any severe weather
- Some of the stronger storms may not be as widespread, but for those who do see development severe warnings will be likely.
- Best chances are in the late afternoon/evening.
- Western and southwest Arkansas have the highest chances for isolated tornadoes.
- Flash flooding could become an issue, especially in eastern Arkansas during large storm complex.
-AW Team
Model use accredited to: http://www.spc.noaa.gov/products/outlook/day2otlk.html - http://models.weatherbell.com/
