Severe Thunderstorm Warning 273, NWS Des Moines, IA

648 
WWUS53 KDMX 311016
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
516 AM CDT FRI AUG 31 2018

IAC001-077-311026-
/O.CAN.KDMX.SV.W.0273.000000T0000Z-180831T1100Z/
Guthrie IA-Adair IA-
516 AM CDT FRI AUG 31 2018

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN GUTHRIE AND
EASTERN ADAIR COUNTIES IS CANCELLED...

The storms which prompted the warning have moved out of the warned 
area. Therefore, the warning has been cancelled.

LAT...LON 4172 9424 4176 9414 4186 9394 4134 9390
      4130 9424
TIME...MOT...LOC 1016Z 239DEG 20KT 4167 9418 4136 9419 

$$

IAC049-121-311100-
/O.CON.KDMX.SV.W.0273.000000T0000Z-180831T1100Z/
Madison IA-Dallas IA-
516 AM CDT FRI AUG 31 2018

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 600 AM CDT
FOR NORTHWESTERN MADISON AND CENTRAL DALLAS COUNTIES...

At 516 AM CDT, severe thunderstorms were located along a line
extending from 9 miles east of Panora to 9 miles west of Winterset,
moving northeast at 25 mph.

HAZARD...60 mph wind gusts and quarter size hail.

SOURCE...Radar indicated.

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees.

Locations impacted include...
Winterset, Adel, Dallas Center, Earlham, De Soto, Van Meter,
Redfield, Dexter, Minburn, Winterset-Madison County Airport and
Badger Creek State Park.

This includes Interstate 80 between mile markers 97 and 115.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4172 9424 4176 9414 4186 9394 4134 9390
      4130 9424
TIME...MOT...LOC 1016Z 239DEG 20KT 4167 9418 4136 9419 

HAIL...1.00IN
WIND...60MPH
 
$$

Beerends

548 
WWUS53 KDMX 311026
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
526 AM CDT FRI AUG 31 2018

IAC049-121-311100-
/O.CON.KDMX.SV.W.0273.000000T0000Z-180831T1100Z/
Madison IA-Dallas IA-
526 AM CDT FRI AUG 31 2018

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 600 AM CDT
FOR NORTHWESTERN MADISON AND SOUTHWESTERN DALLAS COUNTIES...

At 525 AM CDT, a severe thunderstorm was located over Earlham, or 11 
miles northwest of Winterset, moving northeast at 20 mph. The 
northern storm that was previously in this warning, and is moving 
across central and northern portions of Dallas County has weakened 
below severe limits. Small hail to the size of dimes will still be 
possible with the northern storm near Dallas Center and Minburn. 

HAZARD...60 mph wind gusts and quarter size hail.

SOURCE...Radar indicated.

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees.

Locations impacted include...
Winterset, Adel, Earlham, De Soto, Van Meter, Dexter and Badger Creek
State Park.

This includes Interstate 80 between mile markers 98 and 115.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4154 9424 4159 9413 4167 9393 4138 9390
      4135 9423
TIME...MOT...LOC 1025Z 242DEG 19KT 4147 9416 

HAIL...1.00IN
WIND...60MPH
 
$$

Beerends

561 
WWUS53 KDMX 311034
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
534 AM CDT FRI AUG 31 2018

IAC049-121-311043-
/O.CAN.KDMX.SV.W.0273.000000T0000Z-180831T1100Z/
Madison IA-Dallas IA-
534 AM CDT FRI AUG 31 2018

...THE SEVERE THUNDERSTORM WARNING FOR NORTHWESTERN MADISON AND
SOUTHWESTERN DALLAS COUNTIES IS CANCELLED...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning has been cancelled.  However small hail, gusty
winds and heavy rain are still possible with this thunderstorm.

LAT...LON 4154 9424 4159 9413 4167 9393 4138 9390
      4135 9423
TIME...MOT...LOC 1033Z 244DEG 19KT 4149 9410 

$$

Beerends

Area Forecast Discussion
National Weather Service Des Moines IA
426 AM CDT Fri Aug 31 2018

.SHORT TERM.../Today through Tonight/
Issued at 356 AM CDT Fri Aug 31 2018

This morning we have a shortwave pushing across mainly the
southern half of the state. Strong forcing and threat-e advection
resides across southwest Iowa and will track into eastern Iowa by
this afternoon. Thunderstorms have blossomed in this environment
aided by a low level jet focused into the area and will track
mainly across southern Iowa through 12Z. At the surface there is a
warm front across the forecast area. Surface analysis shows the
front to exist from roughly Estherville to east of Lamoni. The
front will move little through 18Z...especially the northern
extend of the boundary. The current convection that is confined to
southwest Iowa will likely quickly expand as the shortwave
encounters the frontal boundary. This looks to occur roughly
around the I-35 corridor around 12Z and reach the eastern portion
of the forecast area by 15Z. There is a lot of instability over
the state and shear of 30-40kts is sufficient for storms to be
organized and produce large hail.

There will be a few hours break this afternoon. However by mid to
late afternoon through tonight, another shortwave will traverse
central into northern Iowa. By 00Z the surface low which the warm
front was attendant to will push into north central or
northeastern MN and a cold front will stretch from that low into
SW MN and NE Nebraska. Re-initiation of storms will occur likely
near the frontal boundary during peak heating but there is also
strong theta-e advection occurring ahead of the boundary in SE
Nebraska and west central to SW Iowa. Storms could also re-develop
in this area as well. The storms will then move into western Iowa
during the late afternoon and evening and as a low level jet
becomes re-established later this evening, storm coverage will
again expand across central Iowa.

Shear this evening will be stronger...in the 50-60kt range so
very large hail and damaging wind will be likely with the storms.
There is a slight risk out for this area for that reason. Hires
models indicate that storms will become more of a wind threat
overnight...especially across northern Iowa. Near the location of
the frontal boundary an isolated tornado cannot be ruled out
especially early on in the event. In addition...PWATS this evening
now exceed 2 inches so heavy rainfall is also a threat. The
heaviest rain tonight will likely be in a different area from the
current and this morning's rainfall so flooding is not a concern
as yet but with several nights of this repetitious pattern to
go...this will be watched as it will likely become a concern down
the road.

.LONG TERM.../Saturday through Thursday/
Issued at 356 AM CDT Fri Aug 31 2018

Little has changed over the past 24 hours regarding the extended
with an active, wet pattern setting up now through much of next
week. Southwesterly upper level flow pattern in place Saturday
through the middle/end of next week with a broad upper level trough
building into the desert southwest and remaining nearly stationary
across the area through the period. Energy will continue to lift out
ahead of the parent trough with a number of shortwave troughs moving
through the region through the duration of the forecast period. At
the surface, a boundary will remain in place across the state and
will somewhat waffle back and forth across the state through the
extended range. Abundant moisture advection into the state with a
fetch off the the Gulf and from the Baja region of Mexico. This will
keep PWAT values up around seasonally high levels in the
neighborhood of 1.5 to 2 inches through much of the week with the
average for this time of year usually around 1 inch. This will also
usher in a return to more humid conditions with dewpoints expected
to be in the 60s/70s for much of the week and seasonal max
temperatures in the lower 80s. With the series of shortwave troughs
allowing for periods of thunderstorms every day, especially during
the diurnally favored times of late afternoon into the
evening/overnight hours, there will be an increasing flood/flash
flood threat through the period. Initially this weekend, some of the
different chances for storms will likely be spread out hitting
different portions of the state, but into the middle of next week
with several rounds of heavy rainfall potential likely river
flooding seems likely especially in areas that have already been
wetter this season along with flash flooding where soils are moist
from recent heavy rains over the past week or two.

Overall severe threat for Saturday into Sunday is smaller with deep
layer shear limited at times around 25-30 kts or less and decent
instability. A few severe storms still likely through the weekend,
with large hail and damaging winds the main threats given more
linear wind profiles, although some turning in the lowest levels
will aid in a non-zero tornado threat especially in areas near the
sfc boundary. Have continued with mainly broad-brushed pops from
guidance blend grids through the entire extended, with the greatest
pops most days in the overnight hours Saturday night and Sunday
night when heavy rainfall likely with each wave moving through and
the LLJ increasing and being oriented straight into central Iowa
through the weekend.

&&

.AVIATION.../For the 06Z TAFS through 06Z Friday night/
Issued at 1159 PM CDT Thu Aug 30 2018

Latest hires models have pulled back the timing of convection
until past 10z Friday. Looks to be mainly along I-35 and then push
east, so diminished the amount of time for thunder mentioned at
FOD. Higher confidence storms will impact DSM, MCW, and ALO during
the morning hours. A break is likely late in the morning Friday
before redevelopment seems reasonable during peak heating over the
south. After 18z Friday, low confidence with timing and duration
of convection in the afternoon and slightly higher confidence
with storms developing with the LLJ during the evening hours
Friday.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SHORT TERM...FAB
LONG TERM...Beerends
AVIATION...Podrazik

Hazardous Weather Outlook
National Weather Service Des Moines IA
316 AM CDT Fri Aug 31 2018

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-011100-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun-
Webster-Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene-
Boone-Story-Marshall-Tama-Audubon-Guthrie-Dallas-Polk-Jasper-
Poweshiek-Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union-
Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-
Appanoose-Davis-
316 AM CDT Fri Aug 31 2018

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

Strong to possibly severe storms will be possible at times through
the day, with chances increasing this evening into the late night
hours. Large hail and damaging wind are the main threats along
with locally heavy rainfall. A tornado chance cannot be ruled out
later today.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Periodic storm chances continue Saturday through Thursday. There
is a chance for strong to possibly severe storms Friday through
Sunday night. Large hail and damaging winds will be the main
threats. Localized heavy rainfall will be possible with all of the
storm chances. River flooding and flash flood threats could
increase into next week with several rounds of possibly heavy
rainfall expected through the weekend into next week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed today and tonight, and possibly
into the weekend at times.

MJB

Special Weather Statement
National Weather Service Des Moines IA
437 AM CDT FRI AUG 31 2018

IAZ058-059-071-311000-
Guthrie IA-Adair IA-Dallas IA-
437 AM CDT FRI AUG 31 2018

...GUSTY WINDS TO 50 MPH ACROSS GUTHRIE COUNTY...

At 437 AM CDT, Doppler radar was tracking a strong thunderstorm near
Stuart, or 11 miles southeast of Guthrie Center, moving northeast at
25 mph.

Wind gusts up to 50 mph will be possible with this storm.

Locations impacted include...
Stuart, Panora, Redfield, Dexter, Diamondhead Lake, Menlo and Linden.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4174 9429 4152 9410 4150 9419 4150 9424
      4149 9424 4146 9439 4157 9449
TIME...MOT...LOC 0937Z 237DEG 20KT 4155 9437

Beerends