Watching Friday’s Severe Weather Potential
The NAM has had a rough go of it lately. It’s reliability past 48 hours has been worthless in my opinion and now it seems to be wanting to come into agreement with some of the other models about tomorrow’s set-up. Once again it appears to me as if KC will be on the fringe of a severe weather set-up that will need to be monitored for any northwards adjustment. It’s certainly not clear cut, and my feeling is that IF there is going to be a risk, it’s later in the day as opposed to earlier in the day. There are major questions about how unstable we’ll get closer to the metro area. It appears the more instability will reside about 50-100 miles S/SW of the metro.
The front that came across the region last night, and shunted the record heat towards the south of the area, will be retreating northwards tonight and tomorrow. This is a set-up for at least the chance of some scattered convection tomorrow AM, especially south of KC. While our air here has dried out, there is a decent amount of gulf moisture (dewpoints near 70°) residing towards the Southern Plains states. Here is the dewpoint map showing the thicker surface moisture towards OK & TX.
The shaded areas represent dewpoints greater than 56°. The medium GREEN areas represent dewpoints 64° or greater. So the surface moisture is there but a look at the soundings this AM from the balloon launches in Norman and Dallas indicate that the moisture is very shallow and not deep through the lower part of the atmosphere.
One of the big issues for us is that the winds tomorrow will be from the SE at the surface. This will not exactly be tapping into the rich moisture source for the metro or for areas towards the N of KC. Here is the NAM forecast for FRI @ 7PM…I’ve outlined the area that I think needs to be watched for some strong to potentially severe storms.
Click on that image to make it larger.
The SPC generally has the same area outlined. I may have outlined the farther SE position a little to far SE, they may very well be capped closer to the bootheel.
The next map I’m going to show you is the CAPE forecast. CAPE is a way that we can judge the instability in the atmosphere. Notice it paints NO instability at all for the metro vicinity. Also notice the blue lines. Those represent what is called Helicity or the tendency of the air to have a corkscrew rotation to it. Those numbers are through the roof which is indicative of the SE surface winds and as you go up in height the winds turn clockwise towards the SW which is a strong indicator for the potential of rotating storms. The thing is, you can have all the helicity in the world, but IF there is little to no strong convection, it means nothing really.
Notice how the CAPE shaded areas are being drawn into the surface low from the top map. My guess is that the area from Osage City-Ottawa-Osawatomie-Butler-Clinton needs to be watched moreso.
Should there be a northward or southward shift then we’ll have to deal with that. The storms, after forming will be moving towards the ENE to NE, eventually crossing over the warm front, becoming elevated and reducing the severe weather threat the farther NE you go.
There are obviously lots of things that will be watched. More updates will be forthcoming on the weather blog.