National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KTOP 172340
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
640 PM CDT Wed Apr 17 2024

.KEY MESSAGES...

- Severe thunderstorms may develop along a cold front late
  tonight and Thursday morning. Large hail remains the concern.

- Blustery conditions are expected as the front passes Thursday
  with temperatures holding in the 50s for most locations.

- There could be some frost Sunday morning impacting gardeners
  who have plants in the ground.

&&

.DISCUSSION...
Issued at 243 PM CDT Wed Apr 17 2024

19Z water vapor imagery showed a upper wave lifting north over
WI and around a closed upper low over southern Saskatchewan. A
speed max was noted digging southeast across ID and into WY. At
the surface, a weak ridge of high pressure stretched from the
northern high plains across northeast KS. Surface low pressure
was noted over the northern TX panhandle with a warm front to
the east across northern OK and northern AR.

As a shortwave over the northern Rockies continues to propagate east
tonight, models lift the warm front north with dewpoints in the
middle 50s and around 60 advecting into east central Kansas. This
front is progged to push back southeast as a strong cold front
Thursday morning. While models show the better dynamics passing
mainly north of the forecast area, there is expected to be good lift
and frontogenesis with the cold front. Meanwhile the CAMs continue
to struggle developing deep moist convection along the front as it
pushes south. Not sure why this is the case since many of the
forecast soundings show little inhibition with around 2000 J/kg or
MUCAPE. Additionally effective shear is forecast to be upwards of
45KT. So have a 50 to 80 percent chance for storms across northeast
and east central Kansas late tonight and through mid-morning
Thursday in spite of the CAMs. Mid level lapse rates around 8C/km
and the good effective shear argue for large hail being the main
concern. But if a storm is able to move off the front into the warm
sector, forecast soundings show nearly 200 m2/s2 of effective SRH.
Since the main forcing mechanism is the front, it appears unlikely
storms will move ahead of it into the warm sector. Nevertheless
think the tornado risk is non-zero. CAMs are also showing isolated
to scattered storms developing late this evening within the warm air
advection pattern. Instability is more limited for the elevated
parcel within the warm air advection, so the main severe risk looks
to be with the frontal passage.

Models show an expansive stratus deck with the front that hangs in
after the front passes into the early afternoon. This along with
increasing cold air advection may act to keep temps nearly steady
through the day Thursday across east central Kansas. If the sun is
able to break out earlier in the day, highs may be a few degrees
warmer. A strengthening pressure gradient behind the front is also
expected to cause north winds to gust around 40 MPH. If wind speeds
increase much more than the current forecast has, we may need to
consider a wind advisory for a portion of Thursday.

For Friday into next week, models show a quasi zonal pattern across
the the central U.S. with much of the energy remaining to the north
of the forecast area. There are some POPs on Saturday and again
spread through next week. This looks to be for the potential for
weak perturbations within the zonal flow, and operational models
will show some mid level frontogenesis with saturation passing
through from time to time. Confidence in these POPs is low since
models have not shown a lot of consistency. With this in mind have
stuck with the blend and the small POPs in the extended portion of
the forecast. Overall temperature wise, persistent surface ridges
from Canada are expected to keep cooler weather in place with
seasonal or slightly below normal temps. Now that we are firmly in
the growing season, we will need to watch low temps for the coming
days. Sunday morning`s lows are forecast to be in the middle 30s but
there may also be some mid level clouds to inhibit radiational
cooling. So will keep an eye on this in the coming days.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 633 PM CDT Wed Apr 17 2024

Thunderstorms, strong winds and IFR conditions are forecast
during the 00Z TAF timeframe. Scattered storms could develop
late this evening in eastern KS. Confidence is not overly high
on exactly where those storms will occur, so kept VCTS mention
for now. Another round of storms is then expected along a cold
front toward the early morning hours of Thursday. CIGS look to
drop to IFR near the boundary as north winds quickly increase
behind the front. Gusts will approach 30 kts as rain exits the
area by mid morning.

&&

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

&&

$$

DISCUSSION...Wolters
AVIATION...Teefey