KANSAS CITY, Mo. — After a couple of thunderstorms overnight, with not a lot of rain for many areas, today starts pretty gray and cool. So far this month, temperatures are running about 1 degree below average. We did sneak in 80 degrees yesterday and will likely get one more 80-degree day this week (tomorrow).

With the warmup comes gulf moisture and increasing southeast to south winds. That will create instability, and will also allow a rather strong dry line to firm up towards the west of the region, which should serve as a focus to thunderstorms at some point tomorrow evening out there. And then we play the waiting game for their arrival in Kansas City.

So the blog today will be talking about things such as the cap, and CAPE, and triggers, plus a few other things that need to be in place to get things rocking and rolling.

The main concern though for the metro appears to be Tuesday night into early Wednesday morning. And yes, there would be a nighttime tornadic threat with this situation.

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Kansas City forecast:

Today: Clouds hanging around for awhile with afternoon clearing. Cooler with highs in the mid-to-upper 60s.

Tonight: Fair skies and seasonably cool with lows in the 40s.

Tomorrow: Variable clouds, windy and warmer. Highs in the lower 80s. Winds gusting to around 40 MPH. There may be a few showers/storms during the day but odds are most are waiting till nighttime for storms.

Tomorrow night: Severe weather likely. Hail, winds, even a small chance of a possible tornado are on the table for many areas of the region. The highest tornadic risk is towards NW MO and NE KS. Turning colder towards daybreak as readings drop into the 40s.

Wednesday: Blustery and chilly with temperatures only in the 40s. Some showers are possible as well. While I doubt it at this point, someone in the region may actually see a snowflake or two, especially up north.

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Discussion:

Tomorrow is going to be an interesting day in the region. Dew points (surface moisture), thanks to strong south winds, will be surging later in the morning into the afternoon into the 60s. So it will feel like spring in a big way Tuesday.

A dry line, which separates the Gulf moisture from the drier Plains air, will be establishing itself somewhere in central Kansas in the afternoon.

The dry line is important in the process that will be unfolding later in the day. It’s sort of a big irritant to the atmosphere and an area that is monitored for storms to form near.

Ahead of the dry line in eastern Kansas, heat and high dew points will contribute to a VERY unstable atmosphere ready to be tapped into for any storm that moves into its region.

Above us, strong winds aloft will create wind shear. There are several types of wind shear but the two biggies for severe storms are directional wind shear and speed wind sheer. This system will have both working for it.

Directional shear occurs when the winds vary in direction with height. In severe weather scenarios, we watch for southeast or south winds shifting towards the southwest to west component as you go higher in the atmosphere.

For speed shear, we look for the winds to increase with height from a speed standpoint. In the forecast tomorrow: 20-30-plus mph winds at the surface, increasing to 50 to 70 mph as you reach 10,000 feet or above (sort of interesting to see some models try and figure out what happens even higher in the atmosphere this morning).

Then there is the matter of the cap. This is a layer of warm air that keeps a “lid” on rising air bubbles and the instability that builds up below the cap area (and perhaps even above it too). That cap is a deal breaker if strong enough, and one of the many tricks about Tuesday evening especially is when will the cap break.

Here’s something else for you: There should be a raging blizzard happening as all of this is unfolding in the upper Plains area toward North Dakota.

This storm is a powerful one, has a lot going for it, and now we try and figure things out.

Model data has been picking out this potential for over the last week. The issue is how things all come together, especially in relation to when the cap breaks out west, because as mentioned, there are more than a few other ingredients in play for storms to be severe coming into Kansas City.

Severe weather risk in Kansas City

So let’s dive in.

As mentioned, lots of Gulf moisture is in place. Here is a map showing the dew points at 10 p.m. Tuesday night.

Notice how the dew points plunge in central KS, that is the dry line.

Between the warmth and the high dew points, lots of instability builds. During the day the cap should hold things in check mostly.

Here is a map showing the CAPE values. CAPE stands for Convective Available Potential Energy. CAPE values can range from 0 to 6,000. Over 1000 is interesting, over 2000 is noteworthy, and over 3000 is yikes!

With that said, it just depends on the setup. You can get tornadoes with VERY little CAPE, or there may be NO storms at all with very high CAPE… again, it goes back to the setup.

CAPE values at 10 p.m. Tuesday

Now the cap: It will be there, a layer of warmish air holding back vertical development of clouds. That should hold into the later afternoon at least. Then as the sun is setting, we should start seeing cells popping up well west of the metro.

We have several pieces of data that show this. The hi-res NAM for 10 p.m. Tuesday has this look.

Activity well west of the metro. These storms wouldn’t get into the metro until well after midnight, and likely be somewhat weaker by then.

The FV3, sort of a newer model:

A little closer with northwest Missouri and northeast Kansas under the gun before midnight.

Finally, the morning HRRR model:

It’s the same sort of idea, with metro timing after midnight.

As we look at this data, this appears to be a late night/early Wednesday morning affair at this point.

There will be a chance of some lighter showers tomorrow zipping up from the southwest, but they would be flying through the region.

Now we have storms coming into the area after midnight (or close). What severe weather risks are on the table with those storms? Typically with a cooling atmosphere, I’d likely be saying then main threats are winds and hail. Which is true, but the winds below two miles in the vertical are really going to be conducive to storms having the ability of showing low-level rotation.

We look at this by looking at our helicity charts (one of several ways of looking at low level wind shear). At it’s most simple, helicity is a tendency for thunderstorm updrafts to have rotation. Values over 100 are interesting, values over 200 are really interesting, values over 300 are yikes!

Helicity chart at 10 p.m. Remember the storms should still be west of the metro, but coming into these values.

That is a problem, and it’s one of the reasons why there is the chance of additional nighttime tornadoes with this setup. We saw 10 days ago these little areas of rotation along the leading edge of the squall line moving through parts of the area leading to some brief tornadoes in St. Joseph, Missouri and Jefferson County, Kansas.

The same thing could happen, although there are other ingredients that are a bit more in the mix to potentially give us a stronger setup this time through as explained.

The bottom line is to be prepared as best you can for overnight severe weather. This means to have a couple of ways of getting information while you’re sleeping.

That means have the cell phone near your bed, and with the volume and vibration set at max (so hopefully it wakes you up).

Have the weather radio turned on and ready to go. You can’t sleep through that thing.

This may be a situation where if you’re already up and tornado warnings are issued for areas that DON’T include you, you should CALL/TEXT others that ARE in the the path of potential tornadoes to make sure they are awake and in a safe spot.

Overnight severe weather potential scenarios are always a bigger headache for safety. And when folks are trying to sleep or sleeping, it creates more problems. We all may have to work together on this one to keep everyone safe.

For those with storm anxiety, remember the odds of you being impacted directly from a tornado are VERY, VERY low. You just need to be prepared and be ready to get into a safe spot just in case a warning comes out. The warnings may tend to be a bit more pronounced/numerous because of the setup and the fact that it’s an overnight scenario, and it’s better to be safe than sorry.

The feature photo is from Sheila Jackson.

Joe