|Above: A group from Puget Sound, Washington, caught this dramatic photo of a large wall cloud in central Kansas on Tuesday, May 1, 2018. Image credit: Courtesy Michael Snyder, @guyinjeep16.|
Wednesday could bring more tornadoes to the Southern Plains after a record-late start to Oklahoma’s tornado season and a near-record for Kansas. Tuesday saw 21 preliminary tornado reports posted to the NOAA/NWS Storm Prediction Center’s database, most of them in Kansas. These reports may have arisen from as few as seven tornadoes, according to weather.com’s Jon Erdman. Very large hail—up to 4” in diameter—pummeled parts of Kansas and Nebraska. No major damage or injuries were reported.
Oklahoma’s twister-less streak was likely broken on Tuesday afternoon—if just barely—by an apparent landspout (a waterspout-type tornado without a storm-based circulation) north of Buffalo, just a couple of miles south of the Kansas border. Low-level moisture across Oklahoma and Kansas was a bit less than optimal for a widespread outbreak of severe weather, leaving a few storms moisture-starved.
Tornadoes are a distinct threat on Wednesday
SPC’s outlook updated late Wednesday morning included a moderate risk of severe weather (the second most dire category) from central Kansas to western Oklahoma, including the Kansas City area, surrounded by an enhanced risk from western Oklahoma across northern Missouri. Low-level moisture has increased since Tuesday, and an upper-level trough inching toward the Plains will provide more support for severe weather.
A cluster of intense storms is expected to develop Wednesday afternoon in central Kansas near the intersection of a stationary front and dry line. Tornadoes are possible, especially before the storms congeal into a mesoscale convective system (MCS) that could slam the Kansas City and St. Joseph, Missouri, areas with very high wind, very large hail, and torrential rain. The high-resolution NAM and the short-range HRRR models suggest the cities are most at risk between around 6 and 10 PM EDT Wednesday.
|Figure 1. WU depiction of severe weather risk areas as designated at midday Wednesday, May 2, by the NOAA/NWS Storm Prediction Center for Days 1 and 2 (left to right), or Wednesday and Thursday, May 2-3, 2018. The small red area for Wednesday denotes a moderate risk of severe weather, the second-highest of SPC’s five risk categories.|
A more serious tornado threat could erupt on Wednesday afternoon along the dry line from south-central Kansas across western Oklahoma. Here, storms will be more scattered, leading to a better chance of individual long-track supercells that could pack one or more strong tornadoes. Storm-fueling instability will be approaching extreme levels: surface dew points were already approaching a summerlike 70°F at midday Wednesday. Overall, the low-level wind shear is a bit tepid for violent twisters, but the shear may be enhanced at a few locations, especially if a surge develops along the dry line into western Oklahoma.
Recent HRRR runs indicate the storms may congeal into a powerful squall line across or near the Oklahoma City area between around 7 and 11 PM EDT Wednesday. Well to the northeast, models agree on bringing a strong MCS or squall line through the Chicago area between about 6 and 10 PM. Chicago went through both March and April without a single thunderstorm, the first time that’s happened since 1915.
Severe weather will continue Thursday ahead of the slow-moving front across the Missouri and mid-Mississippi valleys. The risk of tornadoes may be lower than on Wednesday as low-level wind shear decreases, although deep-layer shear will be quite strong. Widespread heavy rain, high winds, and large hail could occur, especially over northern Missouri and southern Iowa. Remnants from Wednesday’s storms may interfere with supercell development, adding more uncertainty to the outlook. “A broad range of potential scenarios may unfold on Thursday,” cautioned SPC in its updated Day 2 outlook.
|Figure 2. Simulated radar reflectivity from the HRRR model run launched at 15Z Wednesday, May 2, 2018, suggests that by 22Z Wednesday (5 pm EDT), a large cluster of intense thunderstorms will stretch across central Kansas. Scattered storms—likely including several supercells—are predicted across western Oklahoma, with a potential squall line developiong over southwest Texas. Image credit: tropicaltidbits.com.|
A close shave for tornado-skittish Bennington
The town of Bennington, Kansas had a scary few minutes on Tuesday when a large, highly visible wedge-type tornado moved a few miles west of town (see video above). The twister snapped power lines and damaged homes near Tescott and west of Minneapolis, KS. Because of Wednesday’s ongoing severe weather, it may take another day or two before we have Enhanced Fujita Scale (EF) ratings for this and Tuesday’s other tornadoes.
Back on May 30, 2013, a large, intense twister carried out a leisurely loop west of Bennington that lasted nearly an hour. The tornado steered mostly clear of populated areas, so the limited damage led to an eventual EF3 classification, though mobile Doppler data suggest the peak winds may have been even stronger. “I have never seen such a stationary tornado, especially not for so long and for such a violent tornado,” Joshua Wurman (Center for Severe Weather Research) told Capital Weather Gang in 2013.