Special Weather Statement, NWS Topeka, KS

Area Forecast Discussion
National Weather Service Topeka KS
709 PM CDT Tue Apr 6 2021

...Update to aviation forecast discussion...

.DISCUSSION...
Issued at 320 PM CDT Tue Apr 6 2021

Strong to severe thunderstorms move through the region this
evening/tonight, with large hail and damaging winds the main
threats. Otherwise look for a seasonal and quiet forecast.

Elevated convection worked across the forecast area this morning
and early afternoon, bringing light rain to most locales and
moistening the lower BL in advance of our main event this
evening. Daytime solar insolation helped slow the rate of decay of
these showers, with even a few thunderstorms redeveloping along
the western flank of the convective cloud shield early this
afternoon. However, this complex should continue to slide eastward
and pose little in the way of a threat.

Water vapor imagery shows a compact, negatively-tilted upstream
shortwave/low centered across the UT/WY/CO border region, which
will be the driver for the main convective show this evening.
Return southern flow is well-established ahead of a surface cold
front (visible in satellite imagery) that stretches N to S over
western Kansas, producing temperatures in the upper 70s to low 80s
and dewpoints in the upper 50s to low 60s. Stable billow clouds
have given way to more convective cumulus fields near the frontal
boundary, an indication of destablilzation in the BL. The
approaching upper trough should steadily erode the H700 cap over
the next few hours and result in convective initiation in central
Kansas towards the 22-00Z timeframe.

CAM guidance is in good agreement in the general timing and
progression of the convection through the evening. A modest line-
parallel, storm-relative effective shear component and complex mid-
level hodograph structure should result in quick upscale growth to
multi-cell clusters and eventually a line as the convective cold
pool becomes established amidst DCAPE values of over 1000 J/kg.
Thus, expect that the threat will transition to wind with severe
hail possible with stronger updrafts. The threat for tornadoes is
non-zero towards central Kansas towards sunset with 0-1 km SRH
values of 300-400 m2/s2, but the aforementioned issues with the
mid-level hodographs--resulting in competing updrafts and lower
effective shear values--will certainly not aid in sustained
mesocyclone growth. The cold pool surges E/SE through the early
overnight hours, reaching the Topeka area a little bit before
midnight. Recent HRRR runs have E-W up-shear development along the
interface of the LLJ behind this initial wind surge, thus we will
also need to monitor the threat for heavy rain/flash flooding
throughout the night along and south of I-70 with any training
storms.

The trailing stratiform precipitation shield lingers through the
rest of the night and into the morning on Wednesday. The upper low
dives into western Kansas by 12Z Wednesday. The attendant dry
slot wraps around the southern and eastern flanks of the low by
mid-morning, which may temper the threat of rainfall in eastern
portions of the forecast area during the morning hours. Renewed
convective development is expected along the cold front as it
lifts northeastward through far eastern Kansas. While the best
threat for storms, and even a few tornadoes, will be further east
into MO, will still need to monitor trends in the timing of the
front/upper wave as the ribbon of 60 degree dewpoints is still
very close to the eastern CWA border at 18Z Wed based on the
HRRR.

The upper low slows as it becomes the western flank of a eastern
Great Lakes/Appalachian omega block. Multiple perturbations wrapping
around the cyclone keep cool, cloudy, and damp weather through the
day on Wednesday and even into Thursday in far NE Kansas. Clouds
start to clear in central Kansas late Thursday, allowing
temperatures to warm back up into the 60s for highs. A narrow ribbon
of warmer air preceding our next cold front boosts highs into the
low 70s for Friday, but the cold front moves through in the early
afternoon and keeps the bulk of any convection southeast of the
forecast area. The weekend looks to be quite nice with highs in
the upper 60s to mid-70s and with the threat of any showers coming
late Sunday into Monday as the next northern stream wave in the
caravan approaches from northwest.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 640 PM CDT Tue Apr 6 2021

Thunderstorms anticipated to arrive as early as 03-04Z time frame
right now but could be delayed. Threat should be mostly brief
heavy rain transitioning to moderate rain and wind. Thinking a
short window for LLWS ahead of these storms appears to be very
short, and with slightly stronger surface winds still in place,
have decided to not include at this time. Showers and storms
tonight should maintain MVFR categories but additional wrap around
showers and cooler air into the early morning hours are expected
bring CIGs down to low MVFR and dip into IFR levels. Showers could
linger much of the day over the terminals and would be light.
Right now this idea is reflected in the KMHK forecast but may need
to be spread east into the KTOP/KFOE terminals for the next
forecast update.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 8 PM CDT this evening for KSZ008>012-020>024-
034>039-054-055-058.

&&

DISCUSSION...Skow
AVIATION...Drake

Hazardous Weather Outlook
National Weather Service Topeka KS
833 PM CDT Tue Apr 6 2021

KSZ008>012-020>024-026-034>040-054>056-058-059-080145-
Republic-Washington-Marshall-Nemaha-Brown-Cloud-Clay-Riley-
Pottawatomie-Jackson-Jefferson-Ottawa-Dickinson-Geary-Morris-
Wabaunsee-Shawnee-Douglas-Lyon-Osage-Franklin-Coffey-Anderson-
833 PM CDT Tue Apr 6 2021

This hazardous weather outlook is for east central...north
central and northeast Kansas.

.DAY ONE...Tonight.

A complex of strong to severe thunderstorms is forecast to move
west to east across the region early this evening through the
overnight hours. Damaging winds and heavy rainfall appear to be
the main threats into the overnight period. However, large hail
and a brief tornado can't be ruled out.

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

A strong to severe storm cannot be ruled out in far
eastern/northeastern Kansas around midday on Wednesday, with the
threat of storms rapidly moving east in the early afternoon.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed through tonight.

&&

More detailed information can be accessed at...
http://www.weather.gov/top/sitrep

Special Weather Statement
National Weather Service Topeka KS
940 PM CDT Tue Apr 6 2021

KSZ008-070315-
Republic-
940 PM CDT Tue Apr 6 2021

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL REPUBLIC COUNTY UNTIL
1015 PM CDT...

At 940 PM CDT, Doppler radar was tracking a strong thunderstorm near
Belleville, moving north at 55 mph.

Nickel size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Belleville, Scandia, Munden and Narka.

A Severe Thunderstorm Watch remains in effect until 200 AM CDT for
north central Kansas.

LAT...LON 4000 9737 3993 9737 3968 9764 3973 9785
      4000 9778
TIME...MOT...LOC 0240Z 196DEG 47KT 3984 9770

Flanagan/Baerg

Special Weather Statement
National Weather Service Topeka KS
944 PM CDT Tue Apr 6 2021

KSZ034-070315-
Ottawa-
944 PM CDT Tue Apr 6 2021

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL OTTAWA COUNTY UNTIL 1015
PM CDT...

At 944 PM CDT, Doppler radar was tracking a strong thunderstorm near
Bennington, moving northeast at 35 mph.

Pea size hail and wind gusts up to 50 mph will be possible with this
storm.

Locations impacted include...
Minneapolis, Bennington and Wells.

A Severe Thunderstorm Watch remains in effect until 200 AM CDT for
central and north central Kansas.

LAT...LON 3925 9762 3922 9737 3907 9737 3896 9755
      3896 9772 3904 9781
TIME...MOT...LOC 0244Z 226DEG 30KT 3903 9765

Flanagan/Baerg

Special Weather Statement
National Weather Service Topeka KS
1002 PM CDT Tue Apr 6 2021

KSZ020>022-034>036-070345-
Geary-Clay-Cloud-Dickinson-Riley-Ottawa-
1002 PM CDT Tue Apr 6 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN DICKINSON...NORTHWESTERN
GEARY...NORTHWESTERN RILEY...EASTERN OTTAWA...CLAY AND SOUTHEASTERN
CLOUD COUNTIES UNTIL 1045 PM CDT...

At 1001 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Oak Hill to 3 miles southwest of
Manchester to 3 miles north of New Cambria. Movement was northeast at
45 mph.

Pea size hail and wind gusts up to 50 mph will be possible with these
storms.

Locations impacted include...
Clay Center, Solomon, Wakefield, Miltonvale, Milford, Leonardville,
Morganville, Green, Manchester, Longford, Oak Hill, Niles, Talmage,
Idana, Milford Lake and Moonlight.

This includes Interstate 70 between mile markers 267 and 270.

A Severe Thunderstorm Watch remains in effect until 200 AM CDT for
central, north central, northeastern and east central Kansas.

LAT...LON 3900 9746 3956 9749 3957 9679 3925 9686
      3904 9689 3891 9737 3892 9738 3896 9737
      3896 9751
TIME...MOT...LOC 0301Z 241DEG 39KT 3925 9731 3905 9736 3893 9751

Flanagan/Baerg