Joe’s Weather Blog: We’re about to get some big rain (and maybe some strong storms) (WED-5/5)

Weather Blog

KANSAS CITY, Mo. — Good Wednesday to you… bright and chilly briefly this morning as some areas dropped into the 30s this morning. KCI tanked to 38° and Hiawatha dropped to 31°. Not unusual to have this type of weather in the first half of May. As I mentioned last night, there could’ve been some frost out there as well briefly.

Already though, the temperatures are bouncing up and that will go on through the day despite some clouds moving into the region later today. There may even be a few sprinkles out there somewhere this evening.

The rain chances are going up though heading into early Saturday (perhaps as early as later Friday night) and those rain chances may linger into early Sunday before moving away. Overall, Sunday looks to be the better day than Saturday does. The potential is there for locally heavy rains as well and for someone in the area, maybe some severe weather too.

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Forecast:

Today: Sunny this morning then increasing afternoon clouds. There might be a sprinkle or two somewhere out there late today. Highs around 70°. Light-ish winds.

Tonight: Mostly cloudy with a few showers possible. Not as chilly with lows in the mid 40s.

Tomorrow: A small chance of a morning shower then partly cloudy and a bit cooler with highs in the mid 60s.

Friday: Partly cloudy and pleasant with highs well into the 60s.

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Discussion:

The big weather story in the broad picture is yesterday’s announcement of the changes to the 30-year averages that we’re going to be using now. Every 10 years, the earliest 10 years of a 30-year average (the way we determine the average highs and lows as well as rain/snow annual averages etc) changes. So for example we were using 1981-2010 for the averages. Now we drop the 80s and start and go from 1991-2020 for the averages.

This changes things nationwide and locally. You can clearly see the trends in how the averages have changed over the last 100 years. Can you spot the long term trend?

To be fair, the changes in the previous 30-year averages (1981-2010) and 1991-2020 are pretty minor when it comes to temperatures locally.

You can also see lots of places with around or more than a 1/2 degree difference.

In terms of daily differences, there are some as well, mostly subtle, although there are a couple of somewhat more significant ones.

Note how early December is different on the less cold side, while the first few days of November are a bit cooler.

There are some changes in terms of snow and precipitation. Right now, May and June are tied for being the wettest months at 5.23″ a piece on average. This now changes. May is the new wettest month by itself.

For snow, February is the snowiest month with close to 6″ but overall the snow for the year drops to 18.2″ from 18.8″

For precipitation as a whole, we go up to 39.30″ from our previous annual average of 38.86″ to about a 1/2″ increase in the new averages.

Let’s break down a few of the months. There are some changes, especially in the northern Plains during the Winter/Spring.

Really overall, the northern Plains show a definitive drop in high temperatures with the new averages released.

When you put it all together…

Note the change in average moisture. The deserts are getting even drier and that is going to be problematic (it already is) out there. The western Plains and the Appalachians are wetter over the past 30 years in the new averages.

There has been a definitive trend up in the temperatures, especially in the southwest, but aside from the upper Midwest, all of the U.S. has seen an increase in temperatures.

A lot more to this data another time.

Onto our weather which will now focus on the weekend, especially Saturday.

There is a classic setup to heavy rain producing storms somewhere out there on Saturday. The question is where and if we get into the severe weather risk. On Monday, I told Garry we need to pay attention to the risk on Saturday. On Tuesday, I told Alex we need to watch for severe weather on Saturday, and yesterday on the newscasts I told you that we need to watch for severe weather risks on Saturday somewhere nearby.

A warm/stationary front will be setting up near or south of Kansas City. That means that there will be a sharp change in temperatures in the region. Odds are this map will be changing but it gives you the idea of the range in temperatures.

4 p.m. forecast temperatures on Saturday from the GFS

and the EURO:

The GFS is probably too cool, but you get the point. A warm air mass to the south and a cooler air mass on top of us. These air masses will be battling it out. The more rain to the north, the firmer the battle will be.

In the south, in the warmer air there will be a lot of instability.

This next map shows CAPES or the available instability for storms to feed on:

A lot of energy in central Kansas.

The questions are: 1) Is that energy there or is the front that separates the warm and cool air masses farther north or farther south? Farther north puts us in a trouble spot. 2) A strong low-level jet stream will be feeding over the front to the south. That brings a LOT of lift toward our area, hence the high chance of rain and perhaps locally heavy rains. 3) Do we have to worry about hail from the storms, especially near the front? 4) If the front is to the south of Kansas City, will there be a chance of rotating storms, bringing all modes of severe weather into play including perhaps tornados?

So there are things to work on as we get closer. Warm fronts in May are always concerning in the Plains with big temperature swings.

The SPC is watching from here southwards for potential severe weather.

If the front is well south of the Metro, perhaps some wind gusts and hail would be our main threats locally. The key is where that front sets up, because at the very least it may be between I-44 and I-70.

Flooding could be the biggest issue somewhere out there, especially south of Kansas City. The atmosphere on Saturday will have about 1.5 times the typical amount of moisture for early May in it, so the heavy rain threat is something to watch.

This isn’t set obviously, but the EURO has this much rain from this, ending late Sunday (two days worth).

If the front sets up farther north, then we have a higher severe weather risk, with less overall rain. Farther south, a lower severe weather risk but more rain.

Needless to say, Saturday looks messy and we’ll likely be Weather Aware.

Our feature photo comes from Terri Bruntmyer out in Wood Heights, Missouri in Ray County.

Joe

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