Tuesday, April 19, 2011

Updated: Another Severe Weather Outbreak Likely Today

***Update at 12 Noon:
The image below is a visible satellite picture taken at 12 Noon, zoomed in on the central plains.  The thin yellow lines are surface pressure isobars, and the white wind barbs show the surface wind speed & direction (click to enlarge):


As you can see, a line of towering cumulus clouds extends along the cold front / dryline, from just southeast of Oklahoma City, to the Tulsa area, and on into west-central Missouri.  See the annotated image below with the red arrows pointing out the boundary & line of towering cumulus:


This boundary, and the associated line of towering cumulus clouds, will be what we need to keep an eye on this afternoon.  As the lower-levels of the atmosphere continue to heat-up and become more unstable, and an upper-level weather disturbance approaches from the West, rapid thunderstorm development is likely to take place, most likely toward or after 2pm CDT.

By that time, the boundary will likely have advanced to a position from roughly St. Louis, MO to Springfield, MO to near Ada, OK. 

---------------------------Original Post from this morning:


The above is the latest severe weather outlook for today from the SPC.  Severe thunderstorms are possible anywhere within the area outlined in green.  An enhanced risk of severe storms, including possibly damaging tornadoes, is forecast within the area outlined in red.

Strong thunderstorms are already ongoing this morning across portions of east-central Missouri and Illinois, where a Severe Thunderstorm Watch is currently in effect until 11am CDT:


This present activity is really a completely separate event from what is expected to unfold later today, mainly being the result of strong moisture return across the region from the Gulf of Mexico, overrunning a warm front that stretches across the area.  This activity will continue moving Eastward along and North of the warm front this morning.  Large hail will be possible with some of the stronger storms.

Getting back to the "main event" at hand.... A strong upper-level weather disturbance is moving out over the Rockies this morning.  This disturbance will move into the Plains by afternoon, where conditions will have become very unstable at the surface level.


As shown in the above image, a cold front will extend from an area of low pressure over westcentral or southwest Missouri, southwest across Oklahoma and into the Texas Panhandle by mid-afternoon.  A dryline will extend Southward from some point in central Oklahoma, into western and central Texas. 

Thunderstorms are forecast to develop first over Oklahoma and/or southwest Missouri, along and ahead of the dryline and/or cold front by late afternoon.  Large hail, damaging winds and isolated tornadoes are all possible with this initial development. 

Activity is then expected to develop Northward into Missouri and spread Eastward across adjacent portions of Missouri and Arkansas into the evening hours.  The the threat of tornadoes will increase from southeast Missouri into southern Indiana during the evening hours, as the low-level wind profile becomes even more favorable for such development in those areas.

By late evening and into the overnight hours, activity will likely become more linear in nature, with large hail and damaging winds the greatest threats into the Eastern portions of the severe weather outlook areas.

Residents all across the outlook areas should remain alert today.  Review severe weather safety procedures and be prepared to seek shelter if threatening weather approaches your area.

7 comments:

Shamrock said...

Please tell mw if we are in any danger of tornados tomorrow or tonight. I live in the NE tip of Tennessee-in a town called Butler 37640

Rob In Texas said...

Shamrock, Thanks for the comment. You're fine for tonight. You are very near the SPC's severe weather risk area for tomorrow, however the greatest risk is likely South and East of your area. Check here or at www.spc.noaa.gov in the morning for any updates...

Shamrock said...

Thanks so much! You are very welcome-I love your blog. I check it all the time when the weather acts up. I live in the Smoky Mountains and people here seem to think that makes us tornado proof-I'm not so sure! Thanks so much for your reply.

Shamrock said...

So gimme some good news, Rob and tell me Tennessee is in the clear for severe weather today! We were under tornado watch for a few hours..from 2:45am-8am but not a drop of rain...

Rob In Texas said...

Shamrock, sorry, I just now got the comment notice in my mailbox. I need to check on what's taking so long for those to get to me.

Things literally split and went on either side of you early this morning, just like it looked like it would yesterday.

For the rest of today, the greatest risk of severe weather will be Southeast of your area the way it looks...

Hopefully you at least got some rain, we sure could use it here in central Texas...

Shamrock said...

No need to be sorry. I sat and watched the radar late ladt night and early morning. Storms appeared to be coming right for us, and we were under tornado watch-but, at the last minute they went over us. This actually happens quite a bit with severe weather and this location..which brings me to my next question. Is the fact that I am surrounded by mountains actually acting as a barrier? I'll keep my fingers and toes crossed for rain in Texas!

Rob In Texas said...

Shamrock, thanks again for the comment.

The fact is, tornadoes can occur (and have) in every type of geographical situation across the United States, mountains included. You are right in being suspicious of any claims to the contrary.

With that said, certainly geography does play a role in determining where it is easier for a storm to produce a tornado compared to where it is not. I would classify mountainous areas as 'more difficult' than say somewhere on the plains where the terrain is flat and the storm has easy access to all of the moisture and instability that it needs to become more severe.

Go to this link below and you can read more about a tornado that took place in rugged terrain (and in California, no less!):

http://tornado.sfsu.edu/RockwellPassTornado/index.html