More spectacular weather is coming towards the region into Saturday morning before things quickly go off the rails by later Saturday afternoon and through next week.
An intense heat dome is going to build right on top of the Plains, and as it does so the hot air it generates will suppress any hopes for rain and increase the temperatures and dew points.
This will bring prolonged sultry conditions to the region that will percolate for most of next week.
Ironic in a sense because the latest drought report issued Thursday shows improving conditions in the region with drought removal for some areas. The terrain is mostly lush and green right now, and that too may play a role in temperatures and dew points over the coming 7+ days.
If you’re wanting more rain… not much hopes for anything significant for quite some time.
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One sentence forecast: Delightful August weather through tomorrow with highs in the low to mid-80s and decent humidity levels too!
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Forecast
Today: Sunny and mild with highs in the 82-86° range. Winds will tend to increase to 15-25 mph in gusts as the day moves along.
Tonight: Clear and cool with lows in the upper 50s
Tomorrow: Sunny and mild with highs in the mid 80s
Saturday: Partly cloudy and pleasant for a few hours in the morning then more humid and hotter in the afternoon with highs in the low to mid 90s
Sunday: Sultry with highs in the mid to upper 90s and heat index values 100-110°
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Discussion
Lets start with good news regarding the drought situation. There continues to be improvement. You can see it outside and the monitor confirms what you’re seeing.
On the Missouri side:
On the Kansas side:
And the improvement… Green means better in the map below:
How about over the past five weeks?:
So things have gotten better. Not perfect but better. Drought conditions continue near and south of the US 50 corridor region towards the Lakes and for most of central MO.
August has started wet for most. KCI is running 2″ above average BUT by the time the heat dome is done with us towards next weekend, that surplus will be cut by more than half. Close to five inches of rain at the airport guarantees us to have a wetter than average month of August where 4.24″ is average for the month as a whole.
So let’s dive in on the heat, which is going to be developing and expanding in the Plains over the next 7+ days.
While the weather will continue its near perfect run into Saturday morning, the blast furnace will be kicking in during the afternoon as increasing winds will bring hotter air quickly up I-35 and into the region.
The green terrain and the moist soil conditions will allow a lot of transpiration and evaporation to continue. This will be adding moisture into the lower part of the atmosphere and increasing the dew points quite a bit from morning (comfortable) to early afternoon (less comfortable to sultry).
That will be the beginning of the stretch of miserable weather.
Aloft this will be created by a dome of heat that will be parked in the region for days to come. This dome will be intense and one of the stronger ones we’ve seen in quite some time.
It’s unique in a sense because of its position and strength. The model forecasts up at 18,000 feet (the 500 mb level) show this to be right on top of KC.
Note the numbers that you see. 597… 594… 591 on the lines. Those represent heights in the atmosphere in decameters where the 500 mb pressure level is reached. On this map we drop “0” as the last number.
So what this chart tells me is that at roughly 5,970 meters up or roughly 19,586 feet up into the atmosphere the pressure of the air is 500 millibars. Millibars is a unit of pressure. As those numbers decrease, perhaps during an intense winter upper level low… they can come down significantly.
For example, it’s not unusual to have a 5,400 meter low wander around in the Plains. This would mean that if you go 17,700 feet up, the air pressure would be 500 millibars. See the difference between that and 19,600 feet?
I thought this explanation from the University of Arizona was a good way of thinking about how this all affects the temperatures…
“We will now use the 500 mb height contour pattern to estimate the pattern of air temperature. The height of the 500 mb surface is related to the temperature of the atmosphere below 500 mb — the higher the temperature, the higher the height of the 500 mb level. In other words, the 500 mb height at any point on the map tells us about the average air temperature in the vertical column of air between the ground surface and the 500 mb height plotted at that point. The height pattern tells us where the air is relatively cold and where it is relatively warm (see 500 mb side view.) As a vertical column of air warms up (temperature increases), it expands upward, which raises the 500 mb height. Conversely, as a vertical column of air cools down (temperature decreases), it compacts downward, which lowers the 500 mb height. Therefore air pressure decreases more slowly as you ascend through a warm column of air, compared to a cold column of air”
So with extremely high heights at 500 mbs… that means there’s a lot of heat underneath those higher heights… hence the “dome” of heat that I refer to often.
What makes this somewhat unique is that the extreme heights aren’t common here. I did a whole tweet thread on this a few nights ago. Every day balloons are sent up from various upper air sites, for us the closest is Topeka and they find the 500 mb level and what height it’s at, amongst many other things too!
Here are the highest levels where the air pressure was 500 mbs. NOTE that the #1 reading is erroneous. Bad data point.
Model data is still waffling a bit on the precise intensity of the dome (minor effects on our temperatures in the end) but let’s just say when they launch a weather balloon Sunday or early next week that it finds the 500 mb level at 6000 meters up. You could see the rarity of that in the past.
The last time we had a 6000 meter up 500 mb height was back in August of 2003. In that time these were the highs connected to it.
There was a record high in there at 106°.
Ahhhh but there are differences in the set-up then to now. One of the biggies is that we were coming off the driest July in KC weather history. A whooping .12″ at KCI. So the ground heading into the heat dome then was baked out. Early August of ’03 yielded .6″ of moisture. So the air could get hotter and faster (probably with lower dew points too.
One look around the region today and that is not the case. So that gives pause to going to the extremes that happened in ’03.
Let’s take as an example the bottom case… July of 2018. Here are the corresponding highs.
All above average but not crazy hot and no records.
This is sort of where my head is right now. We’re forecasting mid to upper 90s from Saturday into the end of next week. Some may touch 100° or so, especially in the drier areas, but KCI may never get there. This would likely be our last shot though for the year with this heat dome.
Regardless, persistent high heat and warm overnights will lead to trouble for the vulnerable population in the region in these times. So that will be a concern into next week.
There also isn’t likely to be rain for a LONG time. Model data shows essentially nothing till next Friday or next weekend and that isn’t a lock right now either.
I’ve gotten very long winded in this whole thing… sorry.
I’d be remiss if I didn’t talk about what some in the media or silly social posts may show you over the coming days. No there will NOT BE A HURRICANE in California BUT there may be a weakened tropical system with flooding rains in CA next week.
This is Hillary.
It may be a big rainmaker depending on the uncertain track it takes. Farther east up Baja… big rains for California and others in the deserts.
It’s rapidly strengthening this morning.
In a weird way a combination of our strong heat dome, which will help steer the system northwards and also an upper level wave off the California coast will help to usher the storm potentially into California early next week and its moisture as well. How those other two factors play together will determine how Hillary affects southern California and the deserts.
As it comes northwards off the coast of Baja… the waters cool off quickly. That cuts the energy for the storm off to a large extent. So it will be weakening substantially.
With that said though, with the faster northwards speed it may still be a formidable sub-tropical storm as it comes towards southern California… and that is unusual.
This next image shows the rarity of actual tropical storms to hit that region
Here’s more…
So it’s fascinating but I’m sure the media will have a field day with it. Some higher elevation winds could be a thing as well out there too depending on the rate of weakening.
So while we prepare to roast, this will be an item of weathercasts every so often into the weekend.
OK that’s a long blog! I have tomorrow off, so likely no blog coming.
The feature photo comes from Chuck Carbajal
Joe
