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FXUS63 KEAX 191929 AFDEAX

Area Forecast Discussion National Weather Service Kansas City/Pleasant Hill MO 229 PM CDT Sun May 19 2024

KEY MESSAGES

- A line of thunderstorms capable of producing severe wind gusts will likely move through the region late this evening into early tomorrow morning.

- There will be a conditional threat for strong to severe storms tomorrow afternoon and evening.

- Enhanced risk for severe thunderstorms on Tuesday, with all severe hazards (large hail, damaging wind gusts, and a few tornadoes) possible.

DISCUSSION
Issued at 210 PM CDT Sun May 19 2024

A broad area of west to southwesterly flow remains over much of the central CONUS downstream of a synoptic trough over the Intermountain West. Meanwhile, water vapor imagery shows a shortwave trough over northern AZ and NM, with this expected to move east northeastward with an associated mid level jet max nosing into the central High Plains. This will help initiate storms this afternoon across far SE Colorado, SW Kansas, and the OK Panhandle in vicinity of a surface low and accompanying southward extending dryline. As these storms move east northeast, they should grow upscale into a quick moving MCS capable of producing widespread severe winds, traversing from SW Kansas all the way into eastern Kansas. As the MCS approaches our far eastern Kansas counties by around 10 pm, they should be entering into a slightly less favorable convective environment.
However, most recent CAM guidance does suggest a large bowing squall line capable of producing severe criteria wind gusts moving through the KC metro in the 10 pm to midnight time frame, with this continuing to move eastward through Missouri into the early morning hours, with the damaging wind gust threat diminishing the further east it progresses. 0-3 km bulk shear vectors could also perhaps support some embedded QLCS mesovortices, especially if bowing segments allow for a more favorable orientation of the shear vector with respect to the line itself. The severe threat should be over by around 2 am, but areas of stratiform precipitation may linger for a bit longer. With the overall progressive nature of the MCS, hydro concerns should be relatively low tonight.

Severe chances for Monday is still very much uncertain. New convection may initiate over the area by early to mid morning tomorrow and continue into the early afternoon hours, but these do not appear to pose much of a severe threat. However, another shortwave trough should eject out of the Front Range and into the Plains tomorrow afternoon, deepening the the surface low over Kansas and enhancing low level southerly flow, bringing in upper 60s dewpoints. By late Monday afternoon, model soundings suggest up to 2000 J/kg of ML CAPE over the region with sufficient shear to support organized updrafts. That being said, forcing for ascent will be lacking. It is possible that storms could initiate along a remnant outflow boundary or a differential heating boundary of some sort. If any storm does manage to initiate, it will have the capability to become severe with large hail and damaging winds. CAMs suggest a large MCS developing over SE Nebraska by late tomorrow night as better forcing arrives, and moving eastward into southern Iowa into the early morning hours of Tuesday. It is possible that this could clip portions of northern Missouri, but best chances should stay north of the MO/IA border.

Tuesday afternoon/evening remains our most favorable set up for severe weather across the region as a stronger shortwave trough moves into the Plains with a belt of 80 knot WSW winds at 500 mb overspreading the region. At the surface, the low should deepen and further approach the area, creating surface pressure falls and backing surface winds, yielding even better low level moisture advection into the region. By mid afternoon, our region will be in a very warm, moist warm sector with ML CAPE values at 3000 J/kg or above with very steep mid level lapse rates. Given the aforementioned band of 80 knot mid level winds, deep layer wind shear will be very strong. This pairing of large instability and deep layer shear will support supercells.
Low level wind shear and hodographs will also support a tornado threat, especially if surface winds can back enough to out of the SE. While supercells will be possible out in the open warm sector earlier on in the event, storms will likely quickly grow upscale into linear storm modes later in the afternoon/evening given the strong forcing and advancing cold front. At this point, damaging wind gusts would likely be the primary hazard, especially if any bowing segments develop.

The cold front should clear the region to the east by late Tuesday night into early Wednesday morning, with precipitation exiting with it. High temperatures for Wednesday should be much cooler (mid 70s) behind the cold front, but temperatures should rebound back to the lower 80s by Thursday and continuing into the weekend.
Chances for showers and storms return for Thursday night into Saturday morning.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/
Issued at 1239 PM CDT Sun May 19 2024

Currently VFR at all terminals under mostly clear skies with southerly winds around 10 knots. These conditions should generally persist through the afternoon and early evening hours.
A squall line is likely to impact the terminals around 4z tonight, with moderate rain lowering visibility to around 3SM.
This squall line will also bring gusty WSW winds, with the initial surge of winds on the leading edge of the line potentially as strong as 50 knots. Storms and breezy winds may linger through around 6z, with some light rain potentially lingering through around 10z. Guidance suggests the potential for additional shower development in the 13z to 17z time window, especially in the vicinity of STJ.

EAX WATCHES/WARNINGS/ADVISORIES
MO...None.
KS...None.

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