Flash Flood Watch 1, NWS Topeka, KS

Area Forecast Discussion
National Weather Service Topeka KS
1141 PM CDT Wed May 13 2020

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Thursday)
Issued at 410 PM CDT Wed May 13 2020

As of 2030Z, water vapor imagery shows southwest flow over the
Central Plains with a broad trough in the western US. Embedded in
the southwesterly flow is a weak perturbation over northeastern CO
and southwestern NE. At the surface, low pressure has been deepening
in CO with the warm front still well to our south in northern OK.
The main change in the short-term is the break-up of the stratus in
eastern KS, which has not been handled well by the models. This is
likely due to mesoscale subsidence occurring behind this morning's
showers and weak thunderstorms. With the WAA regime still in place
and the fact that soundings still show a saturated boundary layer
through the afternoon and evening, it's tough to say when or if the
stratus will fill back in this evening in this area, but CAMs do
show showers developing ahead of the chance for storms tonight
mainly near the NE border.

Heading into tonight, the trend has been for storms to develop near
the NE border after 9pm and progress northward. There remains a bit
of uncertainty as to how far south in KS these storms develop, as
some model runs have kept them entirely in NE while others have them
initiating in north central KS near US-36. There was one run of the
HRRR late this morning that brought an isolated cell as far south as
Manhattan, but that appears to be an outlier at this point. In any
case, consensus generally keeps the convection near the 850mb
frontal boundary, which appears to be just north of the KS/NE border
by 06Z. It is also around this time that the LLJ strengthens to 40-
50 kts. With all these factors in mind, this could provide enough
lift in north central KS to overcome the cap. RAP and HRRR soundings
show MUCAPE as high as 2000-3000 J/kg at Concordia, although
effective shear ranges between 25-40 kts -- the RAP and HRRR go up
to 40 kts while the NAM has tended to stay within 35 kts. Large hail
would be the primary threat with any elevated storms that may
develop in this area tonight.

Thursday is when we have the better potential for severe weather in
the area, mainly in east central KS. By morning, the frontal
boundary should be situated from southwest to north central KS, and
there is generally good consensus to bring it near the Kansas
Turnpike by 21-00Z. Storms should initiate along this boundary
during this time frame and exit the area with it by 06Z. NAM and GFS
forecast soundings at Emporia show CAPE of 2000-3000 J/kg, although
bulk shear starts out around 25 kts in the afternoon before
increasing to 40 kts in the evening. With that in mind, there is
better potential for storms to develop with the eroding cap as well
as the instability, but the timing of the shear along with the
boundary placement may be the main piece to monitor to see how
organized updrafts will become. Locally heavy rainfall with any
storms will also be a concern.

.LONG TERM...(Thursday night through Wednesday)
Issued at 410 PM CDT Wed May 13 2020

Storms should be out of the CWA by 06Z Thursday. The boundary
lingers in southeast KS during the day Friday, with some models
trying to bring it slightly back north into east central KS while
others keep it south of the CWA. Saturday the boundary does move
further north with some variation as to how far north. Showers and
thunderstorms will once again return to the area with a more
amplified trough that moves into the area. Areas that see
repeated rainfall may have some flooding concerns if they receive
heavy rainfall on Thursday, but at this time the bulk of the rain
looks to fall on Thursday.

Next week, an amplified ridge returns dry weather to the area
ahead of a deep trough moving onto the Pacific coast. Temperatures
will be in the 70s to start the week, but increase well into the
80s by mid- week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1136 PM CDT Wed May 13 2020

Thunderstorms could impact KMHK by the start of this TAF period.
Further development is expected early this period for the
overnight hours, mainly near and north of terminals. VCTS is
included much of tonight as a result. LLWS still looking likely
for first few hours of this period as the LLJ gets going.
Otherwise, CIGS will bounce around from low end VFR and MVFR
tonight and Thursday. Another round of storms is expected to
develop along a surface boundary Thursday afternoon near
KTOP/KFOE. Timing of initiation is currently expected to be
21/22Z.

&&

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

SHORT TERM...Picha
LONG TERM...Picha
AVIATION...Teefey

Hazardous Weather Outlook
National Weather Service Topeka KS
412 PM CDT Wed May 13 2020

KSZ008>012-020>024-026-034>040-054>056-058-059-142115-
Republic-Washington-Marshall-Nemaha-Brown-Cloud-Clay-Riley-
Pottawatomie-Jackson-Jefferson-Ottawa-Dickinson-Geary-Morris-
Wabaunsee-Shawnee-Douglas-Lyon-Osage-Franklin-Coffey-Anderson-
412 PM CDT Wed May 13 2020

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

.DAY ONE...Tonight.

Additional thunderstorms are possible tonight, especially along
the Nebraska border. Areas along US-36 may see these develop
after 9 pm and continue into the early overnight hours. Some
storms may be severe with large hail and damaging winds as the
main threats.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Severe thunderstorms are possible Thursday afternoon and evening,
especially across east central Kansas. Large hail and damaging
winds will be the primary hazards. In addition, multiple rounds
of heavy rainfall could result in localized flooding.

.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
141 AM CDT Thu May 14 2020

KSZ023-024-140715-
Pottawatomie-Jackson-
141 AM CDT Thu May 14 2020

...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL POTTAWATOMIE AND
SOUTHWESTERN JACKSON COUNTIES UNTIL 215 AM CDT...

At 141 AM CDT, Doppler radar was tracking a strong thunderstorm near
Emmett, moving northeast at 30 mph.

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

Locations impacted include...
St. Marys, Emmett and Potawatomi Reservation.

LAT...LON 3939 9576 3922 9600 3922 9603 3919 9604
      3916 9608 3917 9608 3918 9607 3919 9608
      3919 9610 3920 9611 3919 9612 3927 9623
      3952 9606
TIME...MOT...LOC 0641Z 220DEG 26KT 3927 9608

Teefey

Special Weather Statement
National Weather Service Topeka KS
145 AM CDT Thu May 14 2020

KSZ009>011-140715-
Washington-Nemaha-Marshall-
145 AM CDT Thu May 14 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN NEMAHA...
NORTHEASTERN WASHINGTON AND MARSHALL COUNTIES UNTIL 215 AM CDT...

At 144 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 8 miles east of Mahaska to 6 miles west of
Frankfort. Movement was northeast at 35 mph.

Penny size hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Marysville, Frankfort, Hanover, Axtell, Beattie, Summerfield, Oketo,
Hollenberg and Bremen.

LAT...LON 4000 9618 3999 9615 3962 9650 4000 9731
TIME...MOT...LOC 0644Z 235DEG 30KT 3999 9719 3967 9653

Teefey

Special Weather Statement
National Weather Service Topeka KS
203 AM CDT Thu May 14 2020

KSZ010-011-023-140730-
Pottawatomie-Nemaha-Marshall-
203 AM CDT Thu May 14 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL POTTAWATOMIE...
SOUTHWESTERN NEMAHA AND SOUTHEASTERN MARSHALL COUNTIES UNTIL 230 AM
CDT...

At 203 AM CDT, Doppler radar was tracking a strong thunderstorm near
Wheaton, moving northeast at 35 mph.

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

Locations impacted include...
Blaine, Centralia, Wheaton and Lillis.

LAT...LON 3942 9637 3954 9650 3976 9617 3960 9597
TIME...MOT...LOC 0703Z 235DEG 30KT 3955 9631

Teefey

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