Good morning bloggers,

Today will feature “the cap”. There is a capping layer of warm air moving over Kansas and Missouri today. This cap will erode this evening, but how fast?  Here is the HRRR surface forecast valid at 7 PM this evening:

The dry line will become much more apparent later this afternoon and evening as the dew point contrast increased dramatically. The winds ahead of the dry line will likely be out of the south southwest and behind the dry line out of the west. This is not going to provide a lot of convergence. There likely won’t be enough lift from this feature to break through the cap.  This will be changing between 7 PM and midnight as the cold front catches up with the dry line, overtakes it and moves across later tonight. When this happens thunderstorms may finally form.

We can see the capping layer by looking at this mornings soundings. On this sounding you can see the warm layer above the surface where the red temperature line warms dramatically between the 900 and 800 mb level.  This will prevent cumulus clouds from growing or even forming at all for a long while today. The dilemma on days like this is that if the cap does break then where it does a huge thunderstorm may form. This cap appears quite strong and we are leaning heavily into the cap holding strong until sunset of after sunset.

The SPC has placed the slight risk to be located along and ahead of the dry line and it widens a bit near where the surface low will track in Iowa.  The tornado risk is very low today due to the cap likely holding and surface winds not backing enough. Most of the thunderstorms that do form will most likely be elevated, produce a lot of lightning, and the main severe risk type would be hail.

Let’s see how this evolves today. This is yet another reason why near Kansas City is one of the most difficult locations in the world to forecast the weather.  We quite often don’t get to see anything coming our way until it forms.  Here is the latest HRRR model valid at midnight:

This shows thunderstorms clustered south down the state line around midnight tonight. They begin forming just after sunset.  Have a great day!

Gary