Severe Thunderstorm Warning 245, NWS Des Moines, IA

633 
WWUS53 KDMX 242344
SVSDMX

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

IAC081-242353-
/O.CAN.KDMX.SV.W.0245.000000T0000Z-180825T0000Z/
Hancock IA-
644 PM CDT FRI AUG 24 2018

...THE SEVERE THUNDERSTORM WARNING FOR NORTHEASTERN HANCOCK COUNTY IS
CANCELLED...
    
The severe thunderstorm which prompted the warning has moved out of 
the warned area. Therefore, the warning has been cancelled.

LAT...LON 4320 9309 4295 9323 4308 9349 4325 9349
TIME...MOT...LOC 2343Z 291DEG 22KT 4314 9336 

$$

IAC033-250000-
/O.CON.KDMX.SV.W.0245.000000T0000Z-180825T0000Z/
Cerro Gordo IA-
644 PM CDT FRI AUG 24 2018

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 700 PM CDT
FOR CENTRAL CERRO GORDO COUNTY...

At 643 PM CDT, a severe thunderstorm was located over Mason City
Municipal Airport, or 7 miles west of Mason City, moving east at 25
mph.

HAZARD...Half dollar size hail.

SOURCE...Radar indicated.

IMPACT...Damage to vehicles is expected.

Locations impacted include...
Mason City, Mason City Municipal Airport, Clear Lake, Ventura,
Burchinal, Portland, Clear Lake State Park and McIntosh Woods State
Park.

This includes Interstate 35 between mile markers 185 and 200.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

This storm is producing large hail. SEEK SHELTER NOW inside a sturdy
structure and stay away from windows.

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 4320 9309 4295 9323 4308 9349 4325 9349
TIME...MOT...LOC 2343Z 291DEG 22KT 4314 9336 

TORNADO...POSSIBLE
HAIL...1.25IN
WIND...<50MPH
 
$$

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

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

IAZ004>006-242230-
Kossuth IA-Winnebago IA-Emmet IA-
429 PM CDT FRI AUG 24 2018

...STRONG THUNDERSTORM MOVING ACROSS NORTHERN IOWA ...

At 428 PM CDT, Doppler radar was tracking a strong thunderstorm over
Iowa Lake, or 11 miles south of Fairmont, moving east at 25 mph.

Nickel size hail and winds in excess of 30 mph will be possible with
this storm.

Locations impacted include...
Iowa Lake, Rake and Ledyard.

LAT...LON 4350 9390 4342 9386 4342 9447 4350 9449
TIME...MOT...LOC 2128Z 268DEG 23KT 4348 9441

Boksa

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

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

0528 PM     HAIL             5 SW BUFFALO CENTER     43.33N 94.01W
08/24/2018  E1.25 INCH       KOSSUTH            IA   TRAINED SPOTTER

            50-60 PERCENT OF BEAN LEAVES STRIPPED.
            HAILED 528-535PM. MAINLY DIMES, AS LARGE AS
            HALF DOLLAR. WITH HEAVY RAIN AND 50 MPH
            WIND. THE DURATION OF THE HAIL EVENT WAS 7
            MINUTES.

&&

BSS