680
FXUS63 KTOP 300524
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1224 AM CDT Tue Apr 30 2024

.KEY MESSAGES...

- A period of active weather is expected Tuesday through Thursday
  with several chances for thunderstorms, including the
  potential for severe weather.

- Additional rounds of thunderstorms could lead to heavy
  rainfall and the potential for flooding.

&&

.DISCUSSION...
Issued at 304 PM CDT Mon Apr 29 2024

Quasi-zonal upper level flow exists across the Central Plains this
afternoon between a trough over the Northern Plains and another
system located over the Pacific Northwest and British Columbia. It
has been a quiet and pleasant day across the region behind
yesterday`s cold front with mostly sunny skies, light southwest
winds, and temperatures warming into the 70s. By this evening, a
surface trough becomes more pronounced across the area with subtle
perturbations moving through the zonal flow. Increasing mid-level
ascent and moisture along with steepening lapse rates could lead to
isolated showers and even a rumble of thunder this evening into
early Tuesday. Forecast soundings show abundant dry air below 700mb,
leading to most of this precipitation evaporating before reaching
the ground. Inverted-v soundings do support some stronger wind gusts
reaching the surface if a storm does impact the area.

The Pacific Northwest trough quickly advances east overnight, taking
on a negative tilt as it progresses across the Northern Plains
during the day Tuesday. The surface pressure gradient tightens ahead
of this feature with strong southerly winds boosting dewpoints into
the upper 50s and low 60s. A dryline is progged to make it into
central Kansas before a southeast moving cold front overtakes the
dry line during the late afternoon or early evening. A capping
inversion will likely preclude convective initiation through the
morning and early afternoon, but models show this cap eroding
sufficiently by the late afternoon to support convection. While the
best dynamics will reside north of the area, lift along the
boundaries, particularly near the triple point, and modest large-
scale ascent is expected to be enough to generate scattered
thunderstorms in the 5-7pm timeframe. Surface based CAPE of 2000-
2500 J/kg along with 30-35kt of bulk shear will support supercells
capable of producing large hail and damaging wind gusts. Low-level
hodographs show good curvature as well, supporting a tornado risk.
The front stalls from west to east somewhere across central/southern
Kansas Tuesday evening with the low-level jet continuing to pump
moisture into the region. Flooding is becoming more of a concern
Tuesday evening into early Wednesday, especially for areas where the
boundary stalls and storm motions become more parallel to the front.
The favored location for this to occur looks to be south of
Interstate 70 and could extend into east central Kansas which
remains very saturated from recent rains.

The low-level jet works to lift the front and associate convection
north during the early morning hours Wednesday. The front is progged
to be into Nebraska by Wednesday afternoon as a surface low deepens
across southeast Colorado and a dryline sets up across southwest
Kansas. Uncertainty remains in some of the details of this round of
storms, but a cap may limit convection during the afternoon until
better forcing arrives during the evening. Any isolated storms in
the warm sector will have the potential to produce all severe
weather hazards. With large-scale forcing increasing during the
evening and overnight hours, upscale growth of any dryline
convection seems likely with the potential for an MCS to move across
the central Plains. Damaging wind gusts would be the main hazard
with any MCS that develops. Additional rounds of storms could lead
to heavy rain and flooding across the area.

The surface low moves northeast into Iowa by mid-morning Thursday
with a trailing cold front remaining across northeast Kansas.
Previous rounds of convection and the timing of the cold front will
determine the strength of any storms, but the environment could
support another round of convection Thursday afternoon ahead of the
cold front before it shifts east of the area Thursday evening.
Model spread increases by the end of the week, although the
daytime hours on Friday are trending drier behind the cold
front. Yet another trough ejects across the Plains Friday into
Saturday, increasing chances for showers and storms.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1224 AM CDT Tue Apr 30 2024

VFR conditions are expected for much of the period. A line of
TSRA is forecast to develop near MHK around 22Z then progress
southeast to TOP and FOE in the 23Z-02Z time period. Added VCTS
for now as convection will be scattered in that period. Winds
increase to around 15kts with gusts to 24kts by 15Z, then
increasing to around 23kts with gusts to 34kts by 19Z. Winds
decrease as the front approaches and become southwest. At MHK
winds will shift to the west then northwest around 10kts by 00Z
Wednesday as the front moves through. Winds decrease at TOP and
FOE by 02Z from the southwest around 10kts.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Flanagan
AVIATION...53