Today: Boom or Bust?

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By Scott Roberts

It’s actually difficult to keep this hype-free. I know a lot of outlets have not even attempted, but since that’s our mission I’m going to do my best. See, if things come together the way they are modeled, this could become the second day of major tornadoes in a row — after strong tornadoes ripped the Omaha area yesterday afternoon. But there are concerns with whether this plays out, which is typical on the third day of a multi-day event.

Why is uncertainty typical as we move further into a multi-day event? each day’s storms leave boundaries — sometimes subtle, sometimes obvious — in the atmosphere in their wake. These are typically smaller than can be forecast by computer models until a few hours before the event. Often, they are only observable on visible satellite or in one of the wind modes of the radar. Those mesoscale (storm scale) boundaries can provide just the kick needed to get things going in one place while the town 10 miles down the road sees nothing.

 

As I write this about 9 hours or so before the event gets underway (12 hours ahead of what I expect to be the beginning of the peak period of activity), here’s my best call on where things stand:

Positives

(Factors increasing the storm chances and risks)

  1. The lowest levels of the atmosphere are dripping — air you can wear. As I write this dew points are above 62 degrees as far north as US50 in central Kansas and as far west as Highway 281.
  2. A strong system is developing. The lee-side low, formed as wind in the upper levels crest the Rockies and create low pressure on the east side, is forecast to be around 998mb this evening, not hugely deep but plenty for our purposes.
  3. A sharp dry line is forecast. That will provide a focus mechanism for storms in western and parts of central Kansas (you’ll see this mentioned in the Dodge City discussion below) which will sweep east during the evening and night.
  4. A broad warm sector most of the eastern half of Kansas along with much of Oklahoma, Texas, and Missouri, have warm, humid air in place.

Negatives

(Factors which would tend to limit impact)

  1. While surface moisture is great, it’s not very deep. We’d prefer to see higher moisture at around 3,000 to 10,000 feet up than we have today.
  2. Morning storms in Oklahoma — this will be a key factor. If these sap the moisture flow from the Gulf, or cause the dryline or warm front to move in ways that don’t match current forecast models, that would tend to limit the strength of storms. Note I’m not saying it’ll be much limit to whether we have storms — I’m very sure there will be storms and some will be severe. But monster hail and strong, long-track tornadoes, that I’m a bit less confident of.
  3. Messy storm mode. If we get widespread storms (say, multiple storms in several randomly-selected 50-mile diameter circles, that will lessen the tornado and giant hail risk and make things more garden-variety severe weather. For the higher-end impacts, we’re looking for a cell that’s all alone in good air, separated by 75-100 miles from its nearest competitors.

Model Data

In the last few storm evolutions, the newer model families have been performing really well. The RRFS and MPAS models in particular. In the older model families, the NAM3k has been doing pretty well. That said, there is a lot of agreement between models in the potential, but less agreement in location. Take a look at the model comparisons of predicted radar presentation at 7pm (you may have to tap the GIF image to animate it):

In this loop (again, you may need to click it to see the animation), you see a 12-hour period forecast radar presentation from one of the models — the one I’m relying on most heavily today.

In our member-only section, I look at one frame of that model evolution and show the forecast sounding and hodograph for that location. I restrict this to members because many people don’t have the interest to know the caveats of that particular analysis, and this isn’t an event where I want any chance of generating confusion.

SPC Outlook

The more dominant and supercells that interact with the western and northern edge of the low-level jet are expected to become tornadic. Several strong tornadoes will be likely, and a few long-track EF3+ tornadoes will be possible. In addition to the tornado threat, forecast soundings have 700-500 mb lapse rates near 8 C/km across much of the warm sector this afternoon from north Texas to southeast Kansas. This will be favorable for very large hail, with hailstones over 2 inches in diameter likely with the more intense storms.

Day 1 briefing issued for the 0600z forecast cycle this morning

By Risk

Remember, on these images, hatched areas indicate a 10% or greater probability of a high-end impact within 25 miles of any point in the hatched area.

Flash Flooding and General Flooding also Possible

NWS Discussions

Dodge City (main risk area US 283 to US 281)

We will not know the impact of any southern plains, elevated t-storm activity until mid morning at the earliest. Thus, this discussion gives two scenarios but doesn`t provide a solution as of yet. The Storm Prediction Center indicates 10% chances of a significant tornado within 25 miles of a point confined to a line from eastern Ellis county to eastern Pratt county.

Another area of thunderstorms may form over extreme western Kansas in a corridor of moist and cool upslope flow on the cool side of the aforementioned warm front. Easterly low level winds and south to southwesterly mid level winds would yield a favorable hodograph for rotating, low topped storms, with possibly a small tornado or two, along with some marginally severe hail.

NWS Dodge City Area Forecast Discussion early morning 2024-04-27

Wichita (the office I expect to be seeing the largest impact)

There still is general support with some timing/placement differences in convection developing toward midday with the deeper low level moisture advection somewhere along/just east of the I-135 corridor. The main question/concern is how extensive in coverage this convection may become in the uncapped and increasingly unstable air mass in the open warm sector. If they remain somewhat more widely spaced (even though not necessarily discrete) they will pose a higher probability for large hail and a tornado given the impressive the hodographs in the point forecast soundings. The dry-line will remain more of a focus across west central Kansas during the mid to late afternoon which poses another risk area of significant severe weather/tornadoes. While somewhat more conditional, there appears there could be a window for localized convergence in concert with the stronger forcing for ascent ejecting out ahead of the main upper trough…There is much more confidence in the convective trends by later this evening and tonight where the severe threat will transition more into areas of locally heavy/training rainfall across southeast Kansas where a Flood Watch will remain in effect.

NWS Wichita Area Forecast Discussion early morning 2024-04-27

My Take

Overall Risk, east of US 183 and south of I-70

Storms and damage are possible outside the referenced area, but I expect less intensity and impact.

Selected Locations, Threats and Timing

A reminder on the risk values (we use the SPC risk value names and , generally, the meaning for any particular risk):

Our General Chase Target

Our team for today will make a target and timing decision around 10am today. The blue-bounded area is my take on the area where we’ll be today…the west edge this afternoon, the east edge around or just after dark.

We have quite the group which will be tracking these storms and streaming live. Our live stream is at KSStorm.LIVE

Team vehicle 1:

  • Driver, forecaster: Matthew Harding, 14+ years active chasing
    [ Twitter ]
  • Seat 2, Primary Radar/Reporting: Scott Roberts, 20 years active chasing.
    Callsign KB5TOR [ Facebook ] [ Twitch ] [ YouTube ]
  • Seat 3, Observing & Secondary Radar: Lance Ferguson, 22+ years active chasing.
    KWCH12 Storm Chaser (he’ll be doing the live reports if those happen)
  • Meteorologist, Seat 4: Chance Hayes, retired NWS Wichita Warning Coordination Meteorologist
  • Nowcasting Meteorologist: Brad Ketcham, Retired NWS Wichita Lead Forecaster
    [ Twitter ] [ Facebook ]

Team Vehicle 2:

  • Driver/ Lead: Perry Lambert, Former Cherryvale Police Chief, 29 years active chasing
    [ Facebook ] (Perry will be streaming on Facebook live)
  • Seat 2, Communications: Nolan Banks, 8 years active chasing.
    Callsign KC0QAQ

Safety Reminders

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