Severe Weather: A Tale of Two Storms

There isn’t much change from yesterday’s thinking (see the outlook here). SPC pushed the slight risk about 30 miles further west, but if anything the west edge of severe storm chances is sharper than yesterday. Overall risk of strong tornadoes is much less. Very large hail risk has increased a bit, and covers a larger area.

As mentioned yesterday, most models have severe weather parameters that are nearly off-the-chart. But two issues have always been a problem for this system, and a third has been added.

Moisture: the models show more moisture coming in than I believe we’ll actually see. It’s a side effect of the drought, I think, but models have consistently overdone moisture for some time. The short-term models (HRRR particularly) do better.
Weaker upper support: strongest jet stream-level winds are modeled to arrive after dark. If a storm can break the cap and get into the higher levels, what support is there will be oriented more south-to-north than optimal.
The cap: A layer of warm air in the mid-levels of the atmosphere will act as a lid, either keeping storms from developing at all, or choking them off before they can grow to great heights.

That combination makes the afternoon storms less likely to happen. But sometimes a storm or two can pop though a small weaker spot in the cap, lifted by the dryline in a slightly stronger fashion than the air nearby. Any storm that breaches the cap is likely to go severe very quickly, as it will have a large expanse of sky to pull energy from as well as the off-the-chart severe parameters sitting there waiting to be utilized.

Key thoughts from SPC and NWS

A very favorable supercell environment will develop along and ahead of the dryline from central KS into western/central OK late this afternoon. However, this region will be between the main midlevel trough and surface low to the north, and the ejecting low-amplitude shortwave trough to the south. While guidance generally removes all MLCINH along the dryline, there is very little signal for initiation in this region. An isolated supercell or two cannot be ruled out, but confidence is too low to maintain a 30% hail risk. Please note that a Slight Risk remains across this area, with conditional potential for very large hail and a couple of tornadoes if storms can develop.
Storm Prediction Center, Day 1 Outlook issued 12:59am today

A dryline will set up along or west of the I-135 corridor. The environment will be favorable for severe weather east of the dryline. The dryline will act as a source of lift this afternoon but may not be enough to overcome the cap. Models are currently split on whether or not we stay capped today. The GFS, HRRR/RAP, WRF-ARW, and HRW-FV3 keep us uncapped with the latter two actually developing an isolated supercell. The NAM and WRF-NSSL keep us capped which would put a lid on the first round of storms and we wouldn’t see anything until later tonight. If the cap breaks, isolated supercells will be possible and any storm that develops will have the potential to produce tennis ball sized hail, 60-70 mph winds, and a few tornadoes.

The second round of storms will move into central Kansas tonight around 6z Wednesday. As the cold front over takes the dryline storms are expected to go up and push southeastward. Linear storm mode would be favored with this round of convection so the main hazards would be quarter sized hail and 60 mph winds. Confidence is higher that this round of storms will play out as greater forcing will be available when the cold front approaches.
NWS Wichita, Area Forecast Discussion issued this morning

Intense winds, blowing dust and dangerous wildfire conditions are expected Tuesday afternoon, with unseasonably warm temperatures. A strong cold front will bring strong north winds this evening, followed by dramatically colder air tonight and Wednesday. A few sprinkles or flurries are possible Wednesday, but otherwise the forecast remains dry.
NWS Dodge City, Area Forecast Discussion issued this morning

[O]ne or two storms [may] be triggered by some localized weakening of the cap and quickly turn severe and even produce a late afternoon tornado. It just remains that this scenario is low probability. The cold front into this evening along with the approaching upper trough does bring about the best match for low level convergence and forcing for ascent along with low level winds being further enhanced by the LLJ (low level jet) developing into the evening. Any semi-discrete storm could produce a strong tornado with large hail. But, again, the higher probability scenario at this time will be that shear vectors are oriented more parallel to the boundary and upscale growth takes place quickly into a line of storms.
NWS Topeka, Area Forecast Discussion issued this morning

Bottom Line

We see damaging hail as the primary risk for the eastern half of Kansas today. In the west, the main risk is fire. Tornadoes are possible while storms can stay out of a line. Afternoon storms are less likely but will be the more impactful if they occur. Tonight, a line of storms will focus hail and wind risks into the overnight hours.

Chase Status

We will be in the field this afternoon by 4pm. Starting point is north of El Dorado on US 77. We’ll stage there until we see how things shape out and whether the early storms come to be. Later, I anticipate intercepting the line along US 50 or 56. Bookmark our live stream now | Follow our Twitter Feed for photos and severe weather reports as we send them to the NWS.