Sunrise 6:05 AM   Sunset 8:33 PM Moonrise 2:59 PM   Moonset 2:39 AM

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FXUS63 KTOP 182343 AFDTOP

Area Forecast Discussion National Weather Service Topeka KS 643 PM CDT Sat May 18 2024

KEY MESSAGES

- Low chance for a strong to severe storm along a weak frontal boundary late this afternoon through early evening.

- A more organized cluster of severe storms is forecast to develop across central Kansas Sunday afternoon, impacting much of the area through the evening and overnight periods.

- Additional and yet more uncertain chances for storms exist Monday evening before a stronger cold front increases more widespread storms developing Tuesday late afternoon and evening.

DISCUSSION
Issued at 307 PM CDT Sat May 18 2024

Broad and mostly dry westerly flow in the mid levels this afternoon as a series of upper lows rotate through Canada while the slow moving upper trough edges into the southeast CONUS this afternoon. Weak ridge aloft is present towards northeast Kansas, providing ample sunshine for the state. Readings towards northeast Kansas are on track to reach the upper 80s to lower 90s today, playing on repeat through at least Tuesday as warm, southerly flow dominates the region.

Main feature we are monitoring for the afternoon is a weak frontal boundary dropping southward into east central Kansas, roughly from Council Grove through Topeka and McLouth areas by the 21-23Z time frame. Rising heights aloft and no discernible waves signal that any CI would result from weak frontal convergence during peak heating. Latest sfc analysis has SFC based CAPE values around 3000 J/KG and 0-6 shear values to around 20 kts so any storm that was able to develop would not sustain long before collapsing. Steep low level lapse rates to 750 mb amid the drier air suggest that isolated damaging wind gusts and small hail would be the main hazards if a storm were able to develop (probs are 20-30%). Activity ends by sunset with focus shifting to the west as an MCS is progged to develop across northwest Kansas amid an embedded trough entering NE. These storms will gradually weaken as they skirt far northern Kansas Sunday morning. If storms maintain themselves this far east, cannot rule a few stronger updrafts capable of small hail or gusty winds around 50 mph.

On Sunday, a dryline sets up over southwest Kansas during the daytime hours as an developing sfc trough induces a strengthening pressure gradient, increasing south winds from 10 to 20 mph sustained with gusts to around 30 mph. Depending upon when storms initiate in the afternoon, any CI ahead of the dryline would more likely be supercells capable of all hazards, however the confidence is low for this scenario (20-30%). The more likely scenario is for storms to iniatite by late afternoon along the boundary, entering central and northeast Kansas by early evening as clusters of storms capable of producing damaging wind gusts and large hail. A strengthening LLJ by early evening could enhance the wind threat potential as storms propagate eastward through the CWA overnight into Monday morning.

Activity ends by sunrise Monday, just in time for the next upper trough to arrive by late afternoon. Strong low level moisture transport during the afternoon may bring dewpoints close to 70 degrees by the afternoon. Combined with highs near 90 degrees once again, SFC based CAPE may exceed 4000 J/KG underneath a stout capping inversion layer throughout the CWA Areas for CI center along a northward moving warm front near the KS/NE border, but more likely widespread with the incoming upper trough from western NE by early evening. Confidence in severe storms remains low and conditional, generally focused north of Interstate 70 and dependent upon weak vort maxes within the embedded trough to assist. If storms were to develop, very large hail and damaging wind gusts would be expected.

Confidence in more widespread storms increases(40-60%) Tuesday afternoon and evening as a strong cold front sweeps through the region. Timing of the upper trough axis and steepening midlevel lapse rates with the location of the sfc front will be key in where bulk of convection resides. Latest indications from mid term guidance is persistent in a line of convection forming along the front in the late afternoon/early evening time frame across eastern areas of Kansas before quickly shifting southeast into MO. Effective bulk shear around 50 kts and CAPE values exceeding 4000 J/KG are high indicators for very large hail in addition to damaging wind gusts and perhaps a tornado or two if storms are able to remain discrete.

Cooler more stable airmass arrives for Wednesday, dropping highs back 10-15 degrees into the middle 70s through Thursday. Overall rain chances are minimal with the westerly flow pattern remaining in place, picking up towards the end of the work week as a northern stream upper trough enters the region.


AVIATION /00Z TAFS THROUGH 00Z MONDAY/
Issued at 638 PM CDT Sat May 18 2024

Expect VFR conditions through the next 24 hours. A surface front will stall over or just southeast of the KTOP and KFOE terminals. The boundary will washout as winds become southeasterly through the morning hours of Sunday. Wind speeds will increase from the South-southeast at 12 to 15 KTS with gusts of 20 to 25 KTS through the afternoon hours. Thunderstorm chances will increase Sunday evening into the early morning hours of Monday.

TOP WATCHES/WARNINGS/ADVISORIES
None.

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