Severe Thunderstorm Warning 199, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
314 PM CDT Mon Sep 9 2019

.DISCUSSION.../Tonight through Monday/
Issued at 314 PM CDT Mon Sep 9 2019

Surface boundary has made slow progress north into central Iowa
this afternoon with isolated to scattered convection. Instability
has increased rapidly in the warm sector with 100MB Mixed-Layer
CAPE of around 2000 J/KG in southwest Iowa. There is a very tight
gradient of CAPE along the boundary and this will be the focus
area late this afternoon into the evening of any potential severe
storms. Shear along this boundary is quite robust with bulk
parameters of 30-40kts in the first kilometer. While the low level
shear is quite good along with the 0-3km CAPE of 100-150 J/KG, mid
level lapse rates are somewhat weak. This would suggest an overall
limit on hail size without stronger mid level accelerations.
However, the tornado threat will still remain given the low LCL,
decent low level CAPE and the strong near low level shear. The
main concern will be as storms approach/intersect the boundary
where the increased helicity would support quick spin-ups.

All the activity will lift northeast this evening and will pass
into MN later in the evening. However, additional forcing is
forecast along the low level moisture transport axis overnight
with additional convection. This will produce an axis of storms
from southwest to northeast across the forecast area during the
night which will shift slightly south as a the front heads back
south toward daybreak. Locally heavy rainfall is expected with
the storms as the train over the same areas, although most areas
can handle some decent rainfall. The convection will gradually
subside Tuesday morning with a break from storms for much of the
day as forcing will remain negligible.

Additional convection is expected in Tuesday night/early
Wednesday, primarily across the northern half of the state where
near the location of a warm front. Strong moisture transport into
the boundary overnight will support convection which is expected
to be moving east into Iowa from Nebraska and South Dakota. The
main threat will be from heavy rainfall but some gusty winds are
also expected. With the boundary lifting northward into later
Wednesday/early Thursday, the threat of storms will be relegated
to northern Iowa with warm and humid conditions in central and
southern Iowa. The main western trof approaches on Thursday with a
stronger synoptic boundary crossing the state during the day.
Convection, possibly severe, is expected to cross central into
eastern Iowa by midday into the evening before cooler and drier
air arrives in the wake of the front. Thereafter, much of the
weather will be quiet Thursday night into early next week except
for some threat of storm Saturday night into early Sunday with a
surge of theta-e advection.

&&

.AVIATION.../For the 18Z TAFS through 18Z Tuesday afternoon/
Issued at 1242 PM CDT Mon Sep 9 2019

Warm front is lifting through the state this afternoon with
widespread MVFR to IFR status and fog across northeast Iowa.
Conditions will improve across the northeast as the front
continues to move north into the evening. Convection is forecast
to fire by mid to late afternoon in western Iowa and spread north
and east into the evening. While mainly VFR conditions are
expected at this time, MVFR to isold IFR ceilings and visibilities
are forecast in and around thunderstorms. Elevated convection will
persist near low level moisture transport axis overnight with
occasional MVFR conditions where the showers are occurring. Winds
will be from the south for much of the period and gusty.

&&

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

&&

DISCUSSION...Cogil
AVIATION...Cogil

Hazardous Weather Outlook
National Weather Service Des Moines IA
424 PM CDT Mon Sep 9 2019

IAZ074-075-081>086-092>097-101100-
Marion-Mahaska-Adams-Union-Clarke-Lucas-Monroe-Wapello-Taylor-
Ringgold-Decatur-Wayne-Appanoose-Davis-
424 PM CDT Mon Sep 9 2019

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Tonight

Thunderstorms are possible this afternoon and evening. At this
time, the threat for severe weather is marginal.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Thunderstorms are possible Wednesday and Thursday afternoon and
evenings. A few of these storms could be strong to
severe...especially Thursday afternoon and evening.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time, but cannot be
ruled out later in the week.

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>073-101100-
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-
424 PM CDT Mon Sep 9 2019

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Tonight

Strong to severe thunderstorms are expected into the evening.
Tornadoes and damaging winds are the primary threats, with large
hail a secondary threat.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Thunderstorms are possible Tuesday... Wednesday... and Thursday
afternoon and evenings. A few of these storms could be strong to
severe...especially on Thursday afternoon and evening.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening... and
also again later this week.

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Special Weather Statement
National Weather Service Des Moines IA
505 PM CDT Mon Sep 9 2019

IAZ036-037-048-049-061-092300-
Hamilton IA-Story IA-Jasper IA-Hardin IA-Marshall IA-
505 PM CDT Mon Sep 9 2019

...Gusty Winds Continue to Move through Central Iowa...

At 505 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Boone to Huxley to Saylorville. Movement
was northeast at 50 mph.

Penny size hail and wind gusts up to 50 mph will be possible with
these storms.

Strong thunderstorms will be near...
  Nevada around 515 PM CDT.
  Story City and Jewell Junction around 525 PM CDT.
  Roland around 530 PM CDT.
  State Center around 545 PM CDT.
  Iowa Falls around 555 PM CDT.
  Marshalltown around 600 PM CDT.

Other locations impacted by these storms include Steamboat Rock,
Rhodes, Radcliffe, Iowa Falls Municipal Airport, Union, Melbourne,
Ellsworth, Buckeye, St. Anthony and McCallsburg.

A Tornado Watch remains in effect until 1000 PM CDT for central and
north central Iowa.

LAT...LON 4203 9284 4180 9335 4186 9335 4193 9339
      4221 9370 4221 9381 4256 9322 4256 9315
      4246 9300 4221 9300 4221 9283
TIME...MOT...LOC 2205Z 231DEG 43KT 4209 9386 4191 9361 4169 9362

Small

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
511 PM CDT MON SEP 9 2019

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

0454 PM     TSTM WND GST     4 N NODAWAY             41.00N 94.91W
09/09/2019  E57 MPH          ADAMS              IA   MESONET

            VIA CWOP OBSERVATION.

&&

CC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
520 PM CDT MON SEP 9 2019

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

0435 PM     TSTM WND DMG     MINBURN                 41.76N 94.03W
09/09/2019                   DALLAS             IA   FIRE DEPT/RESCUE

            12 INCH DIAMETER TREE SNAPPED. RELAYED BY
            DALLAS COUNTY EMERGENCY MANAGEMENT. TIME
            ESTIMATED FROM RADAR.

&&

JAZ