Severe Thunderstorm Warning 166, NWS Topeka, KS

Area Forecast Discussion
National Weather Service Topeka KS
637 PM CDT Tue Jul 4 2023

...Update to aviation forecast discussion...

.DISCUSSION...
Issued at 238 PM CDT Tue Jul 4 2023

Key Points:

- Hot Fourth of July with Severe Weather possible this evening and
overnight
- Cool temperatures expected for the remainder of the week with a
warming trend by the weekend.
- Overnight rain chances will be something to watch Thursday into
Friday and Saturday morning. Some storms could be strong to severe.

Taking a look at afternoon water vapor imagery, a closed low is
still situated over central Canada with a trough axis extending
southwestward, weak ridging over the desert Southwest, and a few
shortwaves embedded in zonal flow over the central Plains. Clear
skies and southerly flow have warmed temperatures quickly across
northeastern Kansas with mid 90s common area-wide by 1 PM. Continued
WAA, afternoon mixing, and warm 850/700mb temperatures will continue
to push afternoon high temperatures into the upper 90s and low 100s.
Luckily, surface moisture is fairly shallow and dewpoints are
staying in the low to mid 60s keeping heat indicies just below Heat
Advisory criteria. That said, with the holiday, heat could quickly
cause issues for people that are susceptible, so make sure to find
shade and drink plenty of hydrating fluids this afternoon.

The main focus in addition to the heat will be evening and overnight
strong/severe thunderstorms along a southeast-moving frontal
boundary. Currently, mid-level vorticity maximums advecting east off
the Rockies are providing sufficient support for convection over the
high plains and along a surface trough axis draped across central
Nebraska. This will be the main focal point for strong to severe
storms in northeastern Kansas later this evening and overnight. By
this evening, convection along the frontal boundary will continue
southeast, growing upscale quickly. Deep shear across Nebraska this
afternoon appears much more supportive of organized convection as
guidance keeps only 25-35 knots of shear along the boundary as it
moves into the northern Kansas. The marginal shear should not be
much of a deterrent for convection as lapse rates will be 7.5-8
degrees in the mid-levels with 2500 J/kg of MUCAPE ahead of the
frontal boundary. That said, RAP convective parameters show the best
area for the strongest and most organized convection to be in north-
central and central Kansas before the line of convection outruns
shortwave energy to its north. Storms will be capable of producing
damaging winds and occasional large hail. CAMs have come more into
agreement with the timing of the line as well with convection making
its way into north-central Kansas between 7-9 PM, I-70 by around
midnight, and east-central Kansas by 2-5 AM Wednesday morning. Heavy
rain will also be a concern as well as PWATs will be high (1.5-2")
and training rain and storms behind the boundary will remain
possible.

By around sunrise Wednesday, the surface boundary should be south of
the area. PoPs remain elevated through much of the day Wednesday as
the the 850 front stalls over the area. Expecting only rain and a
few elevated storms, but with cloud cover and CAA behind the
boundary, instability will not be very impressive for strong storms.
High temperatures should be much more pleasant and in the low 80s.
By the late afternoon, CAMs depict convection to redevelop along the
stalled frontal boundary along the OK/KS border. With very large
CAPE values and increasing upper level support from an approaching
mid-level perturbation, a few of these storms could become severe
with damaging winds, and large hail being the main concern. At the
moment, most of the convection appears to stay south of the area
where better instability resides, but cannot rule out a storm or two
south of the Kansas Turnpike.

Surface ridging builds further into the area Thursday, resulting in
mostly dry weather with highs in the low to mid 80s. It is not until
Thursday evening and into Friday morning that low-level flow returns
from the south and begins to bring warm and moisture-rich air back.
A few mid-level vorticity maximums move across the central Plains
early Friday AM with an increasing LLJ. Increasing deep shear to
40-50 knots overhead with elevated instability could result in
elevated supercells capable of large hail and damaging winds
Friday AM. Guidance appears to keep the bullseye for QPF over
central Kansas, but the exact location of the QPF will continue to
be monitored over the coming forecast periods. Regardless,
continued heavy rainfall over areas that will have received a good
rainfall the previous days could lead to localized flooding. A
similar setup overnight into Saturday AM will be possible with
heavy rainfall again a concern across central and east-central
Kansas.

By Sunday and into next week, temperatures warm up closer to the
climate average as weak upper-level ridging slides east.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 633 PM CDT Tue Jul 4 2023

The main hazard for the period will be with storms that move into
the area later this evening into the overnight period. Winds will
be the main hazard for aviation. Have tried to indicate the time
frame with a TEMPO group. This could be changed if the line of
storms developing over north central into eastern Nebraska gain
forward speed and arrive earlier than currently forecast. Showers
linger into the morning and eventual clearing takes place by late
morning into midday with the next risk of storms near the end of
the period.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

DISCUSSION...Griesemer
AVIATION...Drake

Hazardous Weather Outlook
National Weather Service Topeka KS
240 PM CDT Tue Jul 4 2023

KSZ008>012-020>024-026-034>040-054>056-058-059-051945-
Republic-Washington-Marshall-Nemaha-Brown-Cloud-Clay-Riley-
Pottawatomie-Jackson-Jefferson-Ottawa-Dickinson-Geary-Morris-
Wabaunsee-Shawnee-Douglas-Lyon-Osage-Franklin-Coffey-Anderson-
240 PM CDT Tue Jul 4 2023

This Hazardous Weather Outlook is for central Kansas, east central
Kansas, north central Kansas and northeast Kansas.

.DAY ONE...This afternoon and tonight.

Thunderstorms are likely to move north to south across the region
tonight. These storms could pack a punch with wind gusts up to
70 MPH and large hail. Storms are expected to move into north
central Kansas between 7 and 9 pm, and potentially making it to the
I-70 corridor around midnight tonight.

Heat indices are expected to be around 100 degrees between 2 and 7
pm this afternoon. Be sure to drink plenty of water and take breaks
in an air conditioned room.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Thunderstorms remain possible on Wednesday. If a frontal boundary
fails to move far enough south, there could be some risk for severe
storms in the afternoon across parts of east central Kansas.

Another round of thunderstorms is possible late Thursday night and
into Friday morning. These storms may be capable of producing large
hail.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

&&

More detailed information can be found at:
www.weather.gov/media/top/DssPacket.pdf

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