River Flood Watch 49, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
605 AM CDT Mon May 27 2019

.DISCUSSION.../Today through Sunday/
Issued at 420 AM CDT Mon May 27 2019

Two areas of convection currently ongoing across the region. The
initial area of precipitation moving from central Iowa into southern
Minnesota and is associated with the initial wave of theta-e
advection. The second and more intense convection is over southeast
Nebraska and south into Kansas and is associated with stronger
kinematic support with a 60+ kt low level jet. These storms will be
lifting northeast into central Iowa in a few hours and may maintain
an attendant damaging wind threat as they arrive. These storms will
produce a period of heavy rainfall rates though the short residence
time due to forward propagation of the storms will limit the heavy
rain threat overall this morning.  That said, locally heavy rain
remains possible, especially over northern Iowa where the
precipitation region will pivot across the area.  Not planning any
headlines for northern Iowa for today but will continue to monitor
the situation. At this time, planning to cancel the current Flash
Flood Watch over the southwest area after the convection passes
thorugh.

Severe weather chances are the topic for later today and again
Tuesday. Surface low pressure will lift northeast into northwest
Iowa today with the warm front moving north into the state. The
second wave of thunderstorms will lift through this morning. The
boundary layer is expected to quickly destabilize with the warm
front arrival behind this convection and may have renewed convection
quickly firing over central Iowa by late morning then morning east.
This renewed convection may become quickly organized with rotating
updrafts into the early afternoon. Conditions are prime for very
large hail with these storms.  While the greater tornado threat is
into southeast Iowa and northern Illinois, a tornado threat may
extend back into central Iowa should storms become organized quickly
enough given the low LCL heights and sufficient low level shear.

Overnight, much of the area should be devoid of much precipitation
except with some thunderstorm potential over the far south. SPC has
maintained an enhanced risk for severe weather for Tuesday across
southern Iowa. The latest progs have shifted the boundary farther
south than 24 hrs ago. Not buying the farthest south NAM
solution(note the 06z NAM beginning to trend back north)with other
solutions placing the boundary near the IA/MO border Tuesday morning
then lifting it south into southern Iowa as the upper low lifts
northeast into western Nebraska. North of the boundary looks primed
for vigorous elevated convection with a large hail and heavy rain
threat. PWAT values will again be in excess of 1.5 inches aiding in
the potential for heavy rainfall. Very well may need a Flash Flood
Watch for portions of central and southern Iowa for Tue/Tue night
along and north of the boundary. Obviously the enhanced risk region
for severe weather across Iowa is conditional on the boundary
location. Should the convection initiate across southeast Nebraska
into Kansas first, this event may turn more linear as it moves into
Iowa during the evening and overnight and may have an attendant QLCS
tornado threat with 0-3 km shear vector of 30-40 kts with much of
that in the lowest 1 km. Supercells earlier in the event certainly
be possible with the boundary in the state.

Still some uncertainty regarding Wednesday as the boundary remains
over the state. If this occurs, it is plausible that good
destabilization will occur with storms redeveloping during the day
with some severe weather potential. The deep layer shear remains
good on Wednesday so organized storms are certainly possible though
at this time the low level shear is expected to be much weaker than
Tuesday.

Little change beyond Wednesday as the transition to less active
zonal/westerly flow occurs. The best chance for precipitation during
this period will arrive Saturday night as a boundary pushes across
the region.

&&

.AVIATION.../For the 12Z TAFS through 12Z Tuesday morning/
Issued at 601 AM CDT Mon May 27 2019

Thunderstorms will be common across much of Iowa this morning
then will become refocused over the southern portion of the state
this afternoon. Gusty outflow winds will be possible with this
mornings activity. A boundary will settle south later today and
tonight and bring a switch in wind direction and will bring
increasing MVFR to IFR cigs overnight.

&&

.HYDROLOGY...
Issued at 420 AM CDT Mon May 27 2019

Flash flooding remains possible on Tuesday afternoon and night
with heavy rain possible. Headlines may be required with future
forecasts with precipitation of 1 to 3 inches possible along with
locally higher amounts. Have been in collaboration with the NCRFC
and WPC regarding using more that 24 hr QPF in the current river
forecasts to include the Tuesday/Tuesday night precipitation. This
would cause significant changes to several river forecast and
pushing many into minor to moderate flood stage later this week.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 10 AM CDT this morning for IAZ044-045-
057-058-070>072-081>083-092>094.

&&

DISCUSSION...Donavon
AVIATION...Donavon
HYDROLOGY...Donavon

Hazardous Weather Outlook
National Weather Service Des Moines IA
433 AM CDT Mon May 27 2019

IAZ005>007-015>017-023-025>028-033-034-036>038-046-048-049-061-
062-073-074-084-085-095>097-280945-
Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-Pocahontas-
Wright-Franklin-Butler-Bremer-Sac-Calhoun-Hamilton-Hardin-Grundy-
Greene-Story-Marshall-Jasper-Poweshiek-Warren-Marion-Lucas-Monroe-
Wayne-Appanoose-Davis-
433 AM CDT Mon May 27 2019

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

Thunderstorms are likely today...especially through the afternoon
and evening hours. Large hail, damaging winds, and tornadoes are
possible. Heavy rainfall may lead to flash flooding concerns.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Thunderstorms are likely Tuesday afternoon through Tuesday night.
Tornadoes are possible, along with large hail and damaging winds.
Heavy rainfall may lead to flash flooding concerns.

Thunderstorms are possible Wednesday afternoon and evening. At
this time, the threat for severe weather with these storms is low.

Non-severe thunderstorms are possible Thursday afternoon.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening, and
again Tuesday afternoon and evening.

IAZ004-024-035-039-047-050-059-060-075-086-280945-
Emmet-Humboldt-Webster-Black Hawk-Boone-Tama-Dallas-Polk-Mahaska-
Wapello-
433 AM CDT Mon May 27 2019

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

River Flood Warnings are in effect for parts of the area. Please
refer to the National Weather Service website at
weather.gov/desmoines for further details.

Thunderstorms are likely today...especially through the afternoon
and evening hours. Large hail, damaging winds, and tornadoes are
possible. Heavy rainfall may lead to flash flooding concerns.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

River Flood Warnings are in effect for parts of the area. Please
refer to the National Weather Service website at
weather.gov/desmoines for further details.

Thunderstorms are likely Tuesday afternoon through Tuesday night.
Tornadoes are possible, along with large hail and damaging winds.
Heavy rainfall may lead to flash flooding concerns.

Thunderstorms are possible Wednesday afternoon and evening. At
this time, the threat for severe weather with these storms is low.

Non-severe thunderstorms are possible Thursday afternoon.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening, and
again Tuesday afternoon and evening.

IAZ044-045-057-058-070>072-081>083-092>094-280945-
Crawford-Carroll-Audubon-Guthrie-Cass-Adair-Madison-Adams-Union-
Clarke-Taylor-Ringgold-Decatur-
433 AM CDT Mon May 27 2019

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

A Flash Flood Watch is in effect for the area through this
morning. Please refer to the National Weather Service website at
weather.gov/desmoines for further details.

Thunderstorms are likely today...especially through the afternoon
and evening hours. Large hail, damaging winds, and tornadoes are
possible. Heavy rainfall may lead to flash flooding concerns.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Thunderstorms are likely Tuesday afternoon through Tuesday night.
Tornadoes are possible, along with large hail and damaging winds.
Heavy rainfall may lead to flash flooding concerns.

Thunderstorms are possible Wednesday afternoon and evening. At
this time, the threat for severe weather with these storms is low.

Non-severe thunderstorms are possible Thursday afternoon.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening, and
again Tuesday afternoon and evening.

Kotenberg

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
623 AM CDT MON MAY 27 2019

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

0550 AM     TSTM WND GST     5 NW CRESTON            41.11N 94.42W
05/27/2019  M62 MPH          UNION              IA   PUBLIC

            MEASURED ON PERSONAL WEATHER STATION.

&&

RD

Special Weather Statement
National Weather Service Des Moines IA
630 AM CDT Mon May 27 2019

IAZ046-047-058>060-072-073-271200-
Guthrie IA-Boone IA-Greene IA-Polk IA-Madison IA-Dallas IA-Warren IA-
630 AM CDT Mon May 27 2019

...Line of Storms May Produce Winds of 40 to 50 mph...

At 630 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 7 miles northeast of Panora to 7 miles
northeast of Winterset. Movement was northeast at 60 mph.

Winds in excess of 40 mph will be possible with these storms.

Locations impacted include...
Des Moines, West Des Moines, Ankeny, Urbandale, Johnston, Clive,
Altoona, Waukee, Norwalk, Pleasant Hill, Grimes, Perry, Adel, Windsor
Heights, Bondurant, Polk City, Saylorville, Madrid, Ogden and Dallas
Center.

LAT...LON 4210 9397 4163 9343 4126 9388 4178 9434
TIME...MOT...LOC 1130Z 208DEG 52KT 4178 9428 4140 9389

Kotenberg

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