850
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.

&&

$$

DISCUSSION...Prieto
AVIATION...Gargan