Joe’s Weather Blog: Late summer storms to develop (WED-8/24)

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Good evening..thunderstorms are rumbling through the area as I type up this update. The storms so far have shown some weak low level rotation…but also the ability of producing hail to golf ball size.

The air out there is getting worked over from KC northwards…however it it still primed from KC southwards as I type this.

The increasing potential overnight will be the potential of flooding.

So the worst of the severe weather threat will fade after 10PM or so…then the concern shifts to more heavy rainfall through daybreak Thursday.

Forecast:  (updated at 8pm)

Tonight: Periods of thunderstorms likely…continuing into Thursday AM. Some storms may contain hail and gusty winds. Lows tonight near 70. Some locally heavy rains are possible with these storms, including the potential of some flash flooding in some areas depending on where they eventually set up.

Thursday: Lots of clouds and not as warm. There will be some thunderstorm activity out there as well. It now appears that after the AM activity wanes…there could be some new stuff developing in the later afternoon. Highs near 80°

Discussion: (11AM update)

Not exactly a clear cut forecast for the next few days except to say we’re going to have some rather decent chances of rain…including the potential of heavy rainfall in parts of the area leading to the potential of some flash flooding. Also there may be a risk of some severe weather this evening, especially northwest of KC. Hail and wind would be the main threats with that activity.

One problem is the progress of a cold front that is going to move into the area tomorrow AM…then belly up and retreat northwards into the weekend. Another issue will be a low level jet stream that will be an on and off situation into the weekend…

The cloud cover situation that we have out there now will need to change locally for us to get into the potential off round one of storms this evening…we need to build up more instability for the front to work with later today.

The clouds out there now are cutting back on the potential instability…this leads to an atmosphere that isn’t as unstable as what the models may be thinking. The clouds are coming about because of a low level jetstream that is overrunning an outflow that pushed south of the area this morning because of the convection overnight.

Model data indicates the low level jet will weaken and shift towards the east. This should allow the clouds to fade and thin this afternoon…then we should start getting more unstable again.

The cold front in question is lurking towards the NW of the KC area this afternoon.

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11 AM surface map…

Ahead of the front dew points are 70°+ (mostly) and the atmosphere overall is getting more and more juicy. By later this evening there will be a lot of moisture in the atmosphere…this will lead to whatever storms forming having the potential to produce some real heavy rainfall.

Then whatever outflow develops and pushes out from the storms overnight…will then encounter a re-developing low level jetstream that will allow new areas fo rain and storms to form. This means some get more rains…and I can see a path for some areas to get 2-4″ of rain tonight. Not sure if it’s northern MO or a bit farther south.

Here are the current watches from the NWS…the darker green is the Flash Flood Watch.

 

Here is the HRRR model…showing it’s idea of the evolution of things. This model hasn’t been the most reliable…actually none of them have been really lately. The model is via IA State.

We also have flow coming in aloft from the SW to the NE. So should there be any disturbance in the flow move up towards our area…new storms could form. So, in a nutshell, there are numerous ways we can have rain/storms in the KC area and points northwards.

I’m not sure I’m jumping up and down about severe weather chances at this point. Something random could happen…but we have to get much more unstable for that to come into play.

Our region is certainly under a “slight” risk of storms.

Let’s see what develops SW of here later today and moves northeastwards. The satellite pictures do show sunshine towards the south of KC…and this will allow the instability to increase for sure.

The following map shows the CAPE values…and also the cap. Where there is blue shading the atmosphere is capped. Typically we don’t get surface based convection in this type of scenario. Where the red contours are not being capped…this is instability that can be tapped by developing thunderstorms. The higher the instability numbers the better the energy for tapping (more or less).

Whatever front pushes through will get to our south and stall…then retreat northwards. The amount of storms tonight>Thursday will play a role in how far south that front can push. It does appear that at some point Friday the front will stop and retreat northwards into SAT AM. Just more chances of seeing storms/rain with this. So in effect its the front that keeps on giving.

We should be back in the seasonable humid air mass this weekend.

Our feature photo today is of snow..yes snow…in the mountains of CO that fell yesterday. From Bud Simpson taken ten miles east of Mesa Verde National Park, Colorado

Joe

 

 

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