Severe Storm Outlook Narrative (AC)
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Issued by NWS
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301 ACUS01 KWNS 060556 SWODY1 SPC AC 060555 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1255 AM CDT Mon May 06 2024 Valid 061200Z - 071200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FOR PARTS OF WESTERN/CENTRAL/NORTHEAST OKLAHOMA INTO SOUTH-CENTRAL AND SOUTHEAST KANSAS... ...SUMMARY... Numerous severe thunderstorms are expected to develop and move eastward Monday afternoon through Monday night across parts of the southern/central Plains. Multiple intense, long-track tornadoes, very large to giant hail, and severe/damaging winds all appear likely. ...Synopsis... A potent shortwave trough is evident in water vapor imagery this evening within the Great Basin. This feature will continue eastward into the Four Corners by early this morning. An initial speed max is expected to eject into western Kansas. By late afternoon into the evening, another speed max will approach western Oklahoma. Deep low-level moisture is already being observed in the BRO 00Z sounding. Surface observations also show low 70s dewpoint as far north as the DFW Metroplex this evening. As the trough approaches, this moisture should stream northward. The overall synoptic setup indicates a severe weather outbreak occurring this afternoon and extending into the evening and parts of the overnight period. Multiple intense, long-track tornadoes are expected, especially in parts of southern Kansas into Oklahoma. Very-large hail of up 2-4 inches can also be expected with intense supercells. Severe gusts may initially be isolated, but storm coverage should increase with time as well as the mode becoming more linear. As this occurs, severe gusts, some up to 80 mph, will become more common. ...Oklahoma into southern Kansas... Intense storms are expected across these areas by late afternoon. Storm coverage is likely to initially be greatest in south-central Kansas given the greater and earlier upper-level forcing. Isolated storms will still be possible along the dryline in western Oklahoma as strong heating in the Texas Panhandle should support dryline circulations that should at least locally erode inhibition. By the evening, greater forcing for ascent will arrive in western Oklahoma. Flow aloft will be nearly perpendicular to the dryline, which will favor a discrete storm mode. Even as the weak Pacific front overtakes the dryline, low-level forcing is not expected to be strong enough to promote substantial upscale growth, especially when coupled with continued strong shear across the boundary. Overall, there appears to be prolonged opportunity for discrete storms to form across western Oklahoma into parts of southern Kansas. While the environment during the afternoon will certainly support intense, long-track tornadoes, concern only grows by early evening. Discrete storms are expected to move eastward into an intensifying low-level jet core in central and eastern Oklahoma into southeast Kansas. Surface-based activity will likely persist into the evening and even parts of the overnight, given continued influx of moisture and weak capping. The time frame of greatest concern for intense tornadoes is from 03-06Z across central into northeast Oklahoma. This is a high-end environment. An upgrade to a tornado-driven High Risk was considered. There remains some lingering uncertainty with regard to the number of intense tornadoes that will occur. An increase in tornado probabilities will certainly be warranted should confidence in coverage and preferred corridors increase. ...Western Kansas into Nebraska...Iowa...Missouri... Convection will likely initiate in western Kansas into southwest Nebraska earlier than elsewhere given the timing of the upper-level forcing. Furthermore, a linear mode should more quickly become established due to the deep layer shear being oriented much more parallel to the initiating boundary than farther south. Buoyancy will generally decrease with northward extent. That being said, moisture will continue to push northward through the day and into the evening. Mid 60s F dewpoints could reach southeast Nebraska. Strong deep-layer and low-level shear will promote an organized line of convection capable of wind damage and QLCS tornadoes (some potentially strong). There is some potential for discrete storms to form ahead of the anticipated line. These storms would pose a greater threat for significant tornadoes. Large to very large hail will likely be more likely in western and central Kansas and coverage of very large hail will be conditional on how long a discrete mode is maintained. ...South Dakota... Richer low-level moisture (upper 50s to perhaps near 60 F dewpoints) will reach portions of central into northwest South Dakota. A narrow zone of instability is expected to develop by the afternoon between the cold and warm front. Large hail and severe gusts will be the main threats, but low-level shear will be sufficient for a tornado or two. ...Edwards Plateau into Texas Rolling Plains... Storm coverage this far south should generally be much more isolated on account of weak and nebulous forcing. However, a strong enough dryline circulation could initiate convection within a strongly unstable and sheared environment. Should storms form, large hail and severe wind gusts would be possible. ..Wendt/Darrow.. 05/06/2024 $$