Joe’s Weather World: One of the strongest April storms for KC on record (MON-4/8)

Happy Monday…and a phenomenal day on tap today with some of the warmest weather we’ve seen so far this Spring coming our way today. So far the warmest day is 77° this past Saturday…we’ll try to get there today or go above. We’ll be ahead of a very weak front that will slide through the region tonight. It’s impacts tomorrow may be a few degrees but overall it’s warm for a few days…then it won’t be warm again for a while. Wednesday could actually be in the 80s (maybe) ahead of a major and significant storm which is going to bring a terrible April blizzard towards the northern Plains and upper Midwest but strangely in KC may not give us much of anything…except wind.



  • Forecast:

Today: Sunny and mild with highs 75-80°. Not too much wind

Tonight: Fair and pleasant with lows in the 40s

Tuesday: Perhaps a few degrees cooler with highs near 70°…partly cloudy skies.

Wednesday: Windy and warm with highs near 80°



  • Discussion:

For the last 5 days or so I’ve talked about this massive Plains storm that was likely to affect the area during the middle>end of this week…and that is still on schedule. The only real change to thinking was a bit of a slowdown in the arrival of the colder air. That remains on track for sometime early Thursday AM. The weather on Thursday will be substantially colder than the weather on Wednesday by some 30-40 degrees. That doesn’t involve the winds which will make it feel even colder!

So watching the model guidance has led me to wonder (and I’m working on this aspect of the system) just how strong a storm for the month of April is this?

It’s actually and potentially one of the strongest storms in KC history, for the month of APRIL. I want to show you the lowest air pressure records for this month.

Those are a lot of numbers…but we measure air pressure in millibars. On TV we convert the millibars to inches of mercury. For example this morning on TV we’d say the barometer reading is 30.00″. In the world of weather that would convert to 1015 millibars. Millibars is a metric standard used to measure air pressure.

Here is some other information from theweatherprediction.com

“A barometer measures the air pressure. The air pressure is a function of how much air is pressing over an area. Air pressure will change rapidly with a change in altitude. Because of this rapid change with altitude, reported pressure is usually adjusted to sea level. Once all locations are adjusted to sea level then the air pressure can be compared between two places that even have different altitudes. Maps that show pressure adjusted to sea level are called isobaric maps. The isobars connect points of equal pressure. Where the isobars are close together the wind is stronger.

The English units of air pressure are inches of mercury. The metric version is millibars. The average sea level pressure is 29.92 inches of mercury and 1013 millibars. Using these average values it can be determined whether the pressure is above, significantly above, below or significantly below the average value. A few sea level pressure benchmark values follow:

1086 mb (32.08 inches of mercury): Highest Ever Recorded
1030 mb (30.42 inches of mercury): Strong High Pressure System
1013 mb (29.92 inches of mercury): Average Sea Level Pressure
1000 mb (29.54 inches of mercury): Typical Low Pressure System
980 mb (28.95 inches of mercury): CAT 1 Hurricane or a very intense mid-latitude cyclone
950 mb (28.06 inches of mercury): CAT 3 Hurricane
870 mb (25.70 inches of mercury): Lowest Ever Recorded (not including tornadoes)”

end text

So with that knowledge…go back up and look at the map…notice our record low air pressure (for April) is 982.1 millibars (mbs). That’s about 29.00″ of mercury (hg).

That’s really low air pressure. You’ll see it if you have a home barometer.

So this storm, per the model data, and again it’s just model data may be represented by a center with an air pressure of 982 mbs when it passes north of KC early Thursday AM. The map below is for 4AM Thursday when the colder air is getting ready to sweep through KC and wipe away the warm air.

In the above map the black lines are the air pressure lines…they’re called isobars and they represent the same air pressure. For example each individual line shows the same air pressure along that line (or close to it). For KC in the above map (contoured every 2 mbs) we have a forecast air pressure of near 988 mbs. That would NOT be a record. Still really low though. I’m working on the other low air pressures for KC in the past in April.

The lowest air pressure is where the “L” is in the above may…and that is in SW IA. That too is NOT a record for IA…their records are in the upper 970s mbs…still pretty amazing.

So this is just one aspect of the storm.

The record lows were mostly established in early April of 1982 or 1983. There were two storms in back to back years that had extremely low pressure in early April!

Our soon to be massive Plains storm is in the Pacific Ocean…

It will come into the US tonight and head towards the 4 corners early Wednesday…then come out into the Plains on Thursday. As this occurs aloft the strong surface storm will develop and intensify as it moves through the Plains as well. The surface and upper level storms will probably be located on top of each other and when that happens usually the storm slows down to a crawl for awhile…and that is expected to occur on Thursday.

So now it gets weird. This will be a wind maker for sure…especially WED into THU. There should be a drop off in the winds early THU AM before the colder air sweeps into the area.

These winds will bring some moisture northbound BUT that moisture may not be very deep…it may be more shallow. This affects the thunderstorm risks…which right now look to be focused farther northwest and north of KC. There are several reasons why…but this blog is getting too long already.

The end result is that while some activity is possible locally at some point WED into early THU AM…nothing too bad is expected right now. The front coming through early THU AM is also not too favorable for rough storms locally despite the strength of the storm.

The SPC has this area as being watched for severe weather later Wednesday especially.

This will be a fascinating storm on satellite as well. It should look similar to the “bomb” cyclone from last month…it may even have a cleared out center of the storm in SW IA!

Then there is the matter of the circulation of the storm…warm at first…the storm will tap colder air and drive that colder air into the Plains and southwards on Thursday and that will sweep into the area. We’ll probably be well into the 60s THU early AM before daybreak and see plunging temperatures (20-25°) in a one hour time frame near or before daybreak. So in reality…temperatures when most people are awake on Thursday will be in the 40s with wind chills in the 30s. Our official high will occur before 4AM or so. When it drops it will drop.

Here is the NAM forecast for 10AM.

We may go up a couple of degrees in the the afternoon (we may not though too) but my goodness. From near 70° after 12AM to that in about 3 hours or so!

Farther north…yup…with that cold air…yup.

Now some of the 2-3 FOOT totals may be overdone…but this is another devastating storm for the ranchers up there.

The “official” forecast is this…and these numbers below could go upwards.

So how much moisture (for us rain) is forecast with this whole storm.

Amazing…some or many may get less than a tenth of 1″.

It’s something to watch…in case better moisture comes this way and things get more active…but it’s a fascinating storm to watch.

The winds though will be 25-45+ mph with the potential of higher gusts WED and then perhaps a bit less but still maybe 20-40 mph on Thursday.

We need to watch for a secondary storm over the weekend…

Our feature photo comes from Vannie Doty near Paradise, MO

Joe

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