Severe Thunderstorm Warning 246, NWS Des Moines, IA

159 
WWUS53 KDMX 250015
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
715 PM CDT FRI AUG 24 2018

IAC033-069-250045-
/O.CON.KDMX.SV.W.0246.000000T0000Z-180825T0045Z/
Franklin IA-Cerro Gordo IA-
715 PM CDT FRI AUG 24 2018

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 745 PM CDT
FOR NORTHEASTERN FRANKLIN AND SOUTHEASTERN CERRO GORDO COUNTIES...

At 715 PM CDT, a severe thunderstorm was located near Nora Springs,
or 7 miles southeast of Mason City, moving east at 25 mph.

HAZARD...Quarter size hail.

SOURCE...Radar indicated.

IMPACT...Damage to vehicles is expected.

Locations impacted include...
Mason City, Rockwell, Dougherty, Burchinal and Portland. 

This includes Interstate 35 between mile markers 185 and 188.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

To report severe weather contact your nearest law enforcement agency.
They will send your report to the National Weather Service office in
Des Moines .

&&

LAT...LON 4287 9303 4302 9337 4316 9325 4311 9302
TIME...MOT...LOC 0015Z 291DEG 22KT 4307 9311 

TORNADO...POSSIBLE
HAIL...1.00IN
WIND...<50MPH
 
$$

Boksa

214 
WWUS53 KDMX 250033
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
733 PM CDT FRI AUG 24 2018

IAC033-069-250045-
/O.CON.KDMX.SV.W.0246.000000T0000Z-180825T0045Z/
Franklin IA-Cerro Gordo IA-
733 PM CDT FRI AUG 24 2018

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 745 PM CDT
FOR NORTHEASTERN FRANKLIN AND SOUTHEASTERN CERRO GORDO COUNTIES...

At 733 PM CDT, a severe thunderstorm was located over Rockford, or 14
miles southeast of Mason City, moving east at 25 mph.

HAZARD...Quarter size hail.

SOURCE...Radar indicated.

IMPACT...Damage to vehicles is expected.

Locations impacted include...
Rockwell and Dougherty. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

To report severe weather contact your nearest law enforcement agency.
They will send your report to the National Weather Service office in
Des Moines.

&&

LAT...LON 4291 9303 4297 9321 4312 9314 4308 9302
TIME...MOT...LOC 0033Z 291DEG 22KT 4303 9297 

TORNADO...POSSIBLE
HAIL...1.00IN
WIND...<50MPH
 
$$

Boksa

392 
WWUS53 KDMX 250045
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
745 PM CDT FRI AUG 24 2018

IAC033-069-250055-
/O.EXP.KDMX.SV.W.0246.000000T0000Z-180825T0045Z/
Franklin IA-Cerro Gordo IA-
745 PM CDT FRI AUG 24 2018

...THE SEVERE THUNDERSTORM WARNING FOR FRANKLIN AND SOUTHEASTERN
CERRO GORDO COUNTIES HAS EXPIRED...
        
The storm which prompted the warning has moved out of the area.
Therefore, the warning has been allowed to expire.

LAT...LON 4291 9303 4297 9321 4312 9314 4308 9302
TIME...MOT...LOC 0045Z 291DEG 22KT 4303 9297 

$$

Boksa

Area Forecast Discussion
National Weather Service Des Moines IA
337 PM CDT Fri Aug 24 2018

.SHORT TERM.../Tonight through Saturday/
Issued at 336 PM CDT Fri Aug 24 2018

Severe Threat

Short-wave trough and associated low pressure system continue to
move across the central Plains into the upper-Midwest, sweeping a
warm front and cold front through the area. As of 3 PM the a triple
point has developed and is analyzed over the Iowa-Nebraska state
line. Surface flow has remained southwesterly this afternoon
supporting the warm-moist airmass. Thick cloud cover this morning
has moved eastward nearly out of the CWA, leaving clear skies over
most of central Iowa. The CAMs have substantially backed off on
thunderstorm development over the CWA, focusing them more eastward.
However, with ongoing insolation in the mid to late afternoon,
SBCAPE values have recovered to near 2500 J/kg over central Iowa
with 100 hPa MLCAPE near 1000 J/kg, where skies have been clearing
for the last several hours. There are also a few cumulus clouds
beginning to appear, as well as several cloud streets and evidence
of convective rolls. Special 18z RAOB from DVN depicts 7.0C/km lapse
rates between 700 and 500 hPa, with 0-6 KM bulk shear of 55 knots. 0-
1 km SRH was nearly 200 m^2/s^2. Over central Iowa, these values are
likely a tad weaker, but cannot be overlooked. Although the CAMs are
favoring the threat to be more eastward than our CWA, WAA coupled
with the clearing skies and approaching warm front is still
favorable for storm development this afternoon through the evening
along and east of Interstate 35. Storms that do initiate will have
potential to be severe, with large hail and damaging winds being the
main threats. An isolated tornado cannot quite be ruled out yet.

As the system continues to move eastward overnight, a ridge develops
behind it over the central Plains. While not well amplified, subtle
AVA will return to the area of Saturday leading to clear skies and
warm conditions. Afternoon high temperatures will be in the mid 80s
northward, with lower 90s possible southward.

.LONG TERM.../Saturday night through Friday/
Issued at 336 PM CDT Fri Aug 24 2018

Sunday Through Monday...
continues to look like an active wx day. Not too much deviation
from yesterday's forecast, so confidence has increased.
Synoptically, a robust area of high pressure/anticyclonic flow
will be in place across the SE CONUS. Meanwhile, a longwave trough
will reach from Canada, along the Rockies and into New Mexico.
This will sandwich Iowa in strong SW flow. It still appears two
shortwaves will pass through Iowa on Sunday... the first wave
during the morning hours, and the second, more potent, wave during
the evening hours. The first wave, tracing back to near the Four
Corners region, continues to look very weak and disorganized. The
second wave can be traced back to southern New Mexico.

The first wave looks to have some decent height falls with it, but
there is not much in place for a mechanism to get convection to be
surface-based. This wave should also be passing through western to
northern Iowa from around 09z-15Z Sun, which is not a
climatologically favored time for strong convection. So at this
time, am looking at an area of low-impact/low-QPF showers with an
isolated rumble of thunder or two possible.

Sunday evening is when more support arrives, as evidence by a 50KT
LLJ oriented from SW to NE overspreading most of the state.
Instability will be sufficient for convection as MUCAPE values reach
3000 J/KG. There seems to be a concentration of steeper low-level
lapse rates in SW Iowa, coincident with the nose of the theta-e
ridge and strong moisture transport into Iowa. Forecast
hodographs look very impressive across SW Iowa Sunday evening.
Ultimately, am hopeful the SPC will catch on and upgrade the
severe wx threat across SW/western Iowa on Sunday as large hail
and a tornado or two cannot be ruled out at this time. With 850mb
temps pushing +21C to +23C across Iowa, with strong WAA in place,
temps should have no problem reaching the low 90s. Thus have
increased temps vs guidance.

This synoptic/mesoscale setup remains in place for Monday... with
the LLJ/slug of strong moisture transport shifting slightly
eastward. So will have to watch for potentially strong to severe wx
across central to eastern Iowa for Monday evening... though threat
may be lessened.

Tuesday through Thursday...
Long-range models still struggling at timing of cold fropa from
cold front attendant to a sfc low passing along the Canada/US
border sometime on Tuesday. Both the 00z and 12z Fri ECMWF runs
slowed down the progression of the fropa and are in line with the
GFS, which ever so slightly sped up its rendering of the fropa.
Thus have gone with consensus for fropa timing. Notable result is
increased temperatures across central to SE Iowa. Afternoon
convection now possible as well across central Iowa... with strong
to severe thunderstorms certainly unable to be ruled out at this
time.

Very strong push of cold air behind this front as 850mb temps go
from +20C or so at 12z Tue to +13C or so on 12z Wed. Cooler
temperatures short-lived, however as WAA looks to infiltrate Iowa
once again heading into the weekend...

Friday and Beyond...
Conditions beginning to become favorable for well above-normal
temperatures across the upper Midwest. For the past few days, both
long-range models have been hinting at trying to establish
another death ridge across the Ozarks. The good news is there is a
lot of time between now and next weekend for things to change. If
things do not change, 850 temps of +25C would likely be advected
into Iowa, yielding a prolonged period of highs in at least the
mid 80s-low 90s across Iowa.

&&

.AVIATION.../For the 18Z TAFS through 18Z Saturday afternoon/
Issued at 1227 PM CDT Fri Aug 24 2018

Low IFR ceilings will be moving out of the area between 1900 and
2000 UTC. Main concern this afternoon will be the development of
rain showers and thunderstorms. A few thunderstorms could be
severe. At this time, hard to determine if thunderstorms will
directly impact terminals. For now, have left VCTS in most TAFs.
Patchy fog may develop in southwest and northeast Iowa overnight,
dependent on how much rainfall actually occurs. At the end of the
period, conditions will clear up.

&&

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

SHORT TERM...Krull
LONG TERM...Kotenberg
AVIATION...Krull

Hazardous Weather Outlook
National Weather Service Des Moines IA
339 PM CDT Fri Aug 24 2018

IAZ004-015-023-033-034-044>046-057-058-070-071-081-092-252045-
Emmet-Palo Alto-Pocahontas-Sac-Calhoun-Crawford-Carroll-Greene-
Audubon-Guthrie-Cass-Adair-Adams-Taylor-
339 PM CDT Fri Aug 24 2018

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

Isolated thunderstorms will be possible today into the early
evening although most location will remain dry. Marginally severe
hail and wind gusts will be possible with the strongest storms.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Starting Sunday, there will be a thunderstorm threat from time to
time into next week. A few storms on Sunday evening may be strong
to severe, with large hail and an isolated tornado the main
threats.

The overall severe weather threat for next week is unknown at
this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time, though it cannot
be completely ruled out Sunday evening.

IAZ005>007-016-017-024>028-035>039-047>050-059>062-072>075-
082>086-093>097-252045-
Kossuth-Winnebago-Worth-Hancock-Cerro Gordo-Humboldt-Wright-
Franklin-Butler-Bremer-Webster-Hamilton-Hardin-Grundy-Black Hawk-
Boone-Story-Marshall-Tama-Dallas-Polk-Jasper-Poweshiek-Madison-
Warren-Marion-Mahaska-Union-Clarke-Lucas-Monroe-Wapello-Ringgold-
Decatur-Wayne-Appanoose-Davis-
339 PM CDT Fri Aug 24 2018

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

There is a slight risk of severe thunderstorms later this
afternoon into this evening. Scattered strong to severe storms are
expected with large hail and damaging wind. Isolated tornadoes
will also be possible.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Starting Sunday, there will be a thunderstorm threat from time to
time into next week. A few storms on Sunday evening may be strong
to severe, with large hail and an isolated tornado the main
threats.

The overall severe weather threat for next week is unknown at
this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be necessary later today into the evening
across southern Iowa, and cannot be ruled out for next Sunday
evening.

Kotenberg

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
615 PM CDT FRI AUG 24 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0606 PM     FUNNEL CLOUD     4 WSW FOREST CITY       43.24N 93.71W
08/24/2018                   HANCOCK            IA   TRAINED SPOTTER

            TRAINED SPOTTER CALLED IN ROTATION WITH THE
            STORM AND AN ASSOCIATED FUNNEL CLOUD.

&&

Special Weather Statement
National Weather Service Des Moines IA
622 PM CDT FRI AUG 24 2018

IAZ006-007-017-250015-
Cerro Gordo IA-Winnebago IA-Worth IA-
622 PM CDT FRI AUG 24 2018

...STRONG THUNDERSTORMS CONTINUE TO DEVELOP ACROSS FAR NORTHERN
IOWA...

At 620 PM CDT, Doppler radar was tracking strong thunderstorms 7
miles east of Forest City, moving east at 30 mph.

Dime size hail will be possible with these storms.

Locations impacted include...
Forest City, Manly, Thompson, Plymouth, Fertile, Leland, Hanlontown
and Rock Falls.

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 4329 9302 4320 9303 4319 9303 4320 9307
      4326 9353 4327 9381 4338 9378
TIME...MOT...LOC 2320Z 291DEG 23KT 4328 9350

Boksa

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
645 PM CDT FRI AUG 24 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0643 PM     HAIL             1 WNW CLEAR LAKE        43.14N 93.38W
08/24/2018  M1.00 INCH       CERRO GORDO        IA   TRAINED SPOTTER

            TRAINED SPOTTER REPORTED LOTS OF QUARTER
            SIZED HAIL.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
646 PM CDT FRI AUG 24 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0644 PM     HAIL             1 NE CLEAR LAKE         43.15N 93.36W
08/24/2018  E1.00 INCH       CERRO GORDO        IA   TRAINED SPOTTER

            TRAINED SPOTTER REPORTED UP TO QUARTER SIZED
            HAIL.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
653 PM CDT FRI AUG 24 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0645 PM     HAIL             3 NW CLEAR LAKE         43.17N 93.42W
08/24/2018  M1.25 INCH       CERRO GORDO        IA   PUBLIC

            PUBLIC RELAYED A PICTURE OF HAIL LARGER THAN
            QUARTERS VIA TWITTER.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
656 PM CDT FRI AUG 24 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0656 PM     HAIL             CLEAR LAKE              43.14N 93.37W
08/24/2018  E1.25 INCH       CERRO GORDO        IA   TRAINED SPOTTER

            TRAINED SPOTTER REPORTED ONGOING QUARTER TO
            HALF DOLLAR SIZED HAIL.

&&