Special Weather Statement, NWS Kansas City, MO

AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
308 PM CDT Sat Oct 21 2017

.Discussion...
Issued at 303 PM CDT SAT OCT 21 2017

Early afternoon satellite imagery, surface observations and radar
returns all point at a large trough, who's axis is currently
swinging through the Rocky Mountains into the Northern Plains, is
helping push a strong cold front quickly east this afternoon. This
has been well advertised by the many models for many days now, with
details in the latest batch of model runs simply reinforcing the
concerns for strong to severe thunderstorms this evening, though
only for a small window in time.

Winds ahead of the front this afternoon have continued to be very
strong with sustained southerly speeds in the 20 MPH range, gusting
to near 40 MPH, thanks to the mixing ahead of the front and a strong
low level jet, as 850mb winds are noted around 45 to 50 knots. A
little scattering in the skies ahead of the front has allowed
surface temperatures to climb into the low to mid 70s just ahead of
the front this afternoon, resulting in surface CAPE values in
between 1500-2000 J/KG. This has helped kick off a line storms,
currently stretching form Wichita to Topeka; with a fine line of
the actually front still about 20 miles farther back to the west.
Shear is rather strong ahead of the front thanks to the jet
structure, with 45 to 55 knots of Effective bulk shear, oriented
to the northeast, noted with the line of developing storms.
Convection is struggling a little at this time as shear is likely
over powering the instability, but think as the afternoon wears on
there will be sufficient lift, especially as the front catches up
to the line of storms, for the storms to quickly grow upscale
into strong to severe storms. The main mode of severe weather will
be the wind given the orientation of the shear, but strong low
level helicity mean that an isolated tornado can not be ruled out
with storms that might lead the front and/or occur within the
inflection points along the progressive squall line. That said,
the window of opportunity will be a bit small for severe weather
this evening as the progressive front will likely undercut
convection. But, that might then lead to hydrologic concerns as
precipitable water values around 1.4 inches are noted, which will
allow over running moisture to produce several hours of efficient
rain behind the leading line of strong storms. Current forecast of
rainfall totals would be for a widespread inch to to inch and a
half with locally higher amounts around 2 to 3 inches in areas
where discreet embedded circulations enhance rainfall rates.

As for timing...currently, given radar, satellite and model trends,
thoughts are that the main line of strong to severe storms will
start affecting our section of extreme northeast Kansas and
northwest Missouri between now and 5 PM, with the front and
associated storms nosing into the west side of Kansas City between
5 and 6PM, and areas to the south of Kansas City between 6-8 PM,
with areas farther south waiting closer to 8 PM. As the front
undercuts the strong storms, expect the severe threat to taper off
quickly past 8 PM this evening as the line moves east.

Rest of the forecast...Sunday will still be rather nice as wind
speeds will be more in the 5 to 10 MPH range under clearing skies,
allowing afternoon highs to reach through the 60s. However, there
will be some cooler temperatures later this week as a prevailing
northwest flow dominates our section of the Plains States,
allowing temperatures to roller coaster up and down a couple times
this week.

&&

.Aviation...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1247 PM CDT SAT OCT 21 2017

MVFR clouds currently prevail ahead of a cold front that will
sweep across the terminals this evening, roughly between 6 and 8
PM. Winds ahead of the front will be rather strong and gusty, but
anticipate a quick wind shift and strong gusty winds with a line
of storms moving through. Winds behind the front should remain
rather strong till much later tonight when the gradient relaxes.
Clouds are also expected to start clearing and/or lifting early
Sunday morning as the dry air moves in.

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&

Discussion...Cutter
Aviation...Cutter

Hazardous Weather Outlook
National Weather Service Kansas City/Pleasant Hill MO
414 AM CDT Sat Oct 21 2017

KSZ025-057-060-102>105-MOZ001>008-011>017-020>025-028>033-037>040-
043>046-053-054-220915-
Atchison KS-Miami-Linn KS-Doniphan-Leavenworth-Wyandotte-Johnson KS-
Atchison MO-Nodaway-Worth-Gentry-Harrison-Mercer-Putnam-Schuyler-
Holt-Andrew-De Kalb-Daviess-Grundy-Sullivan-Adair-Buchanan-Clinton-
Caldwell-Livingston-Linn MO-Macon-Platte-Clay-Ray-Carroll-Chariton-
Randolph-Jackson-Lafayette-Saline-Howard-Cass-Johnson MO-Pettis-
Cooper-Bates-Henry-
414 AM CDT Sat Oct 21 2017

This hazardous weather outlook is for northwest...north central and
west central Missouri...as well as extreme eastern Kansas.

.DAY ONE...Today and Tonight

 Severe thunderstorms are possible late Saturday afternoon and
 evening. Damaging winds will be the primary hazard however, hail up
 to quarter size will be possible early in the event and a isolated
 tornado cannot be ruled out. Otherwise, lightning and heavy rain
 are likely. The heavy rain may lead to minor river flooding and
 localized flash flooding.

 More detailed information can be accessed at...
 https://www.weather.gov/eax/hwo

.DAYS TWO THROUGH SEVEN...Sunday through Friday

 No hazardous weather is expected at this time.

 More detailed information can be accessed at...
 https://www.weather.gov/eax/hwo

Special Weather Statement
National Weather Service Kansas City/Pleasant Hill MO
412 PM CDT SAT OCT 21 2017

MOZ001-002-011-212145-
Atchison MO-Holt MO-Nodaway MO-
412 PM CDT SAT OCT 21 2017

...SIGNIFICANT WEATHER ADVISORY FOR EASTERN ATCHISON...NORTHWESTERN
HOLT AND WEST CENTRAL NODAWAY COUNTIES UNTIL 445 PM CDT...

At 412 PM CDT, Doppler radar was tracking a strong thunderstorm near
Craig, or 11 miles northeast of Falls City, moving northeast at 55
mph.

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

Locations impacted include...
Tarkio, Fairfax, Craig, Quitman, Corning and Indian Cave State Park.

This includes Interstate 29 between mile markers 92 and 104.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

A severe thunderstorm watch remains in effect until 1000 PM CDT for
northwestern Missouri.

LAT...LON 4056 9526 4037 9500 4014 9543 4016 9544
      4018 9548 4020 9548 4022 9547 4025 9549
      4026 9555 4027 9556
TIME...MOT...LOC 2112Z 224DEG 46KT 4021 9548

Barham

Special Weather Statement
National Weather Service Kansas City/Pleasant Hill MO
417 PM CDT SAT OCT 21 2017

KSZ025-212145-
Atchison KS-
417 PM CDT SAT OCT 21 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN ATCHISON COUNTY
UNTIL 445 PM CDT...

At 417 PM CDT, Doppler radar was tracking a strong thunderstorm over
Horton, moving northeast at 45 mph.

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

Locations impacted include...
Muscotah and Huron.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

A severe thunderstorm watch remains in effect until 1000 PM CDT for
northeastern Kansas.

LAT...LON 3950 9557 3965 9556 3965 9532 3949 9557
      3950 9558
TIME...MOT...LOC 2117Z 222DEG 39KT 3962 9553

Barham

Special Weather Statement
National Weather Service Kansas City/Pleasant Hill MO
451 PM CDT SAT OCT 21 2017

KSZ025-102-MOZ020-212215-
Doniphan KS-Atchison KS-Buchanan MO-
451 PM CDT SAT OCT 21 2017

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN DONIPHAN...ATCHISON
AND SOUTHWESTERN BUCHANAN COUNTIES UNTIL 515 PM CDT...

At 450 PM CDT, Doppler radar was tracking a strong thunderstorm over
Effingham, or 11 miles northeast of Valley Falls, moving northeast at
50 mph.

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

Locations impacted include...
Atchison, Effingham, Rushville, Lancaster, Denton, Doniphan,
Farmington, Huron, Cummings and Bendena.

A severe thunderstorm watch remains in effect until 1000 PM CDT for
northeastern Kansas...and northwestern and west central Missouri.

LAT...LON 3965 9535 3965 9534 3966 9534 3981 9519
      3964 9491 3953 9508 3953 9510 3952 9510
      3942 9527 3942 9544 3948 9553
TIME...MOT...LOC 2150Z 222DEG 43KT 3949 9538

Barham