Special Weather Statement, NWS Topeka, KS

Area Forecast Discussion
National Weather Service Topeka KS
1158 AM CDT Fri Jun 11 2021

...MESOSCALE and AVIATION UPDATE...

.MESOSCALE DISCUSSION...
Issued at 1158 AM CDT Fri Jun 11 2021

A special soundings released at 16Z shows a substantial capping
inversion still in place over northeast KS with 700MB temps
at +14C. With the lack of synoptic forcing for vertical motion or
dynamic cooling, we may be relying on heating of the very moist
boundary layer and/or local convergence along the outflow and
frontal boundary for new storm development. This cap lends to more
uncertainty in the timing of storms, and may be the reason some
of the CAMs are struggling with the storm evolution. Given the
amount of instability, the forecast continue to call for storms to
develop/move south through eastern KS through the day.

Storms in southeast NEB have shown better storm structure with
the RAP suggesting 0-6km bulk shear of 40KT. So there could be a
greater potential for hail than earlier expected if updrafts are
able to briefly organize and develop some mid level rotation.

&&

.DISCUSSION...
Issued at 343 AM CDT Fri Jun 11 2021

Main challenges are thunderstorm potential and heat today into
this evening.

A potent shortwave trough was rotating northeast out of the northern
Rockies early this morning with an associated cold front draping
southwest into western Nebraska. Most convection has been in the
Dakotas but development continues to take place into central
portions of Nebraska. The upper ridge axis remains in place across
the central Plains with dewpoints in the middle 70s across southern
Kansas.

Short-range guidance is consistent with the cold front sliding on
southeast into the northwest counties late this morning and on
southeast through the CWA by early evening. Changes from guidance
from 24 hours ago include a much weaker cap and stronger instability
for mixed layer parcels and have higher confidence in thunderstorms
developing through the area during the afternoon in this higher
instability. ML CAPE values reach around 4000 J/kg by late morning
in deep shear of 20-30 knots supporting at least brief large hail,
mitigated by hodographs that wrap over themselves. Pre-frontal
downdraft CAPE values are commonly in the 1000-15000 J/kg range for
a downburst wind threat. PWs in the 1.5 to 2 inch range bring some
heavy rain potential as well but seeing little evidence of training
or persistence of storms to overcome rather high flash flood
guidance values from the recent dry spell to bring a significant
flooding threat. The slower trend of the front and its associated
convection should bring high temps back to the lower to middle 90s
and heat index values of 100-104 in mainly east-central Kansas for a
few hours, but the short duration and some question on
frontal/precip timing keeps confidence too low for a Heat Advisory.

Thunderstorms should diminish in coverage and intensity this evening
with little support beyond the exiting front/outflow, giving rise to
a mainly dry forecast again through the middle of next week as the
upper ridge builds again over the Rockies and Plains. Surface high
pressure to the in generally located over the mid-Mississippi Valley
keeps dewpoints from supporting excessive heat but air temps will
be in the upper 80s to mid 90s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1158 AM CDT Fri Jun 11 2021

Main challenge is timing TS through the afternoon. Some
uncertainty as a result of higher convective inhibition and
inconsistent CAMs makes it more challenging. The inhibition may
require a longer period of heating the boundary layer for storms
to develop near the terminals unless outflow from storms to the
north surges south. As a result, may be a little more broad with
the window of time storms could impact the terminals. If storms
move in, expect VSBY to be restricted by +RA and strong wind
gusts causing IFR conditions. Otherwise I think VFR conditions
should prevail once the storms move south this evening. There is
some signal for MVFR CIGS to linger but confidence in this is to
low to include in the forecast at this time.

&&

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

MESOSCALE...Wolters
DISCUSSION...65
AVIATION...Wolters

Hazardous Weather Outlook
National Weather Service Topeka KS
847 AM CDT Fri Jun 11 2021

KSZ008>012-020>024-026-034>040-054>056-058-059-121400-
Republic-Washington-Marshall-Nemaha-Brown-Cloud-Clay-Riley-
Pottawatomie-Jackson-Jefferson-Ottawa-Dickinson-Geary-Morris-
Wabaunsee-Shawnee-Douglas-Lyon-Osage-Franklin-Coffey-Anderson-
847 AM CDT Fri Jun 11 2021

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

.DAY ONE...Today and Tonight.

Severe thunderstorms with damaging winds around 70 mph and
torrential rainfall leading to localized flash flooding are
possible across northeast, east central and parts of north central
Kansas. Areas along and east of a line from Washington to Abilene
stand the better chances of seeing severe weather. There may also
be some hail with the thunderstorms. Storms could enter northeast
Kansas as early as 10:30 this morning and the risk for severe
weather is expected to last into the early evening as storms
generally move south into east central Kansas through the
afternoon.

Heat indicies are expected to reach 100 to 105 this afternoon across
east central Kansas before thunderstorms move through the area.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotters should be ready to report severe weather to local
authorities and the National Weather Service in Topeka.

&&

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

Wolters

Special Weather Statement
National Weather Service Topeka KS
1210 PM CDT Fri Jun 11 2021

KSZ011-012-111745-
Brown-Nemaha-
1210 PM CDT Fri Jun 11 2021

...SIGNIFICANT WEATHER ADVISORY FOR NEMAHA AND NORTHWESTERN BROWN
COUNTIES UNTIL 1245 PM CDT...

At 1210 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 7 miles west of Bern to 3 miles north of
Baileyville to 4 miles south of Axtell. Movement was southeast at 25
mph.

Wind gusts up to 50 mph will be possible with these storms.

Locations impacted include...
Sabetha, Seneca, Centralia, Morrill, Bern, Goff, Oneida, Baileyville
and Woodlawn.

A Severe Thunderstorm Watch remains in effect until 300 PM CDT for
northeastern Kansas.

LAT...LON 4000 9563 3978 9580 3963 9594 3975 9624
      3992 9624 4000 9617
TIME...MOT...LOC 1710Z 295DEG 24KT 3998 9611 3989 9616 3980 9626

Omitt