Flood Stage Change for the West Fork Des Moines River J e f f Zo g g , S e n i o r H yd r o l o g i s t

The Weather Whisper

May 2019 Volume 1, Issue 1 NWS Des Moines

Cover Photo Credit:

NWS Des Moines Damage Survey at the Iowa Operator Engineers Training

Facility, northwest of Lacona, Iowa.

The morning of August 20th saw

severe storms across the state pro-

duce 3 tornadoes. Extremely strong straight-line winds also produced

widespread damage within Lacona that

was just as intense as was seen in

some of the tornado impacted areas.

Through coordination with

local officials, on July 19th

the NWS in Des Moines

changed the flood stage for

the West Fork Des Moines

River at Estherville from the

old value of 8 feet to the

new value of 10 feet, or an

increase of 2 feet. The NWS

periodically works with local

officials to evaluate flood

stages—and changes them if

necessary—to ensure they

accurately reflect flood-

related impacts.

The NWS considers various

factors in evaluating exist-

ing flood stages and making

recommendations for

changes including a statisti-

cal analysis—analysis of

past crests on the river—and

more importantly, flood-

related impacts. A good

rule of thumb is for the river

to reach flood stage around

once every other year, or

from a statistical perspec-

tive, an annual exceedance

probability of around 50%.

In the case of Estherville,

past crests on the river were

reaching the previous flood

stage multiple times per

year. This frequency of oc-

currence was a red flag that

the flood stage may be set

too low. Statistical analysis

showed that for past crests

to reach flood stage around

once every other year, the

flood stage would have to be

raised by around 2 feet.

Despite what the statistical

analysis may show, the ulti-

mate decision in a change to

flood stage rests with flood-

related impacts and local

officials such as emergency

management. Ideally, flood

stage represents the stage

on the river at which

“significant impacts begin to

life and property within the

reach of the streamgage.”

The “reach of the stream-

gage” is a NWS-specified

distance up and down-

stream from the streamgage

within which the readings,

forecasts, and flood warn-

ings are considered to be

valid. When “significant

impacts” occur, water from

the river typically affects

access and egress, and/or

may flood properties. The

NWS often relies on local

emergency management

and community officials to

provide this information. In

the case of Estherville, local

flood-related impacts sup-

ported raising the flood

stage by 2 feet, because im-

pacts at the previous level

were minimal to none.

River forecasts and flood

warnings for Estherville will

continue to be valid along

the reach of the West Fork

Des Moines River extending

from the Iowa-Minnesota

border to near Wallingford,

reflecting the new flood

stage value. The gauge has

been in operation since

1986, is maintained by the

USGS Central Midwest Wa-

ter Science Center, and

funded cooperatively by the

U.S. Army Corps of Engi-

neers and the USGS .

As with other NWS river

forecast points, the NWS

will provide river forecasts

when the observed or fore-

cast stages go above the

Action Stage. For Esther-

ville, the Action Stage was

also changed on July 19th; it

was raised from 6 feet to 8

feet. In addition, the NWS

will issue river Flood Warn-

ings and follow-up river

Flood Statements when the

observed or forecast stages

go above the Flood Stage.

River forecasts for the above

locations will continue to be

available on the NWS Ad-

vanced Hydrologic Predic-

tion Service (AHPS) Web-

site. River forecasts for

these locations are updated

as needed while the stream

remains at or above the Ac-

tion Stage.

“Ideally, flood stage represents

the stage on the river at which

‘significant impacts begin to life

and property...’“

Flooding on the West Fork Des Moines River

at Estherville, Iowa. Images courtesy of Mike

Ehret and where taken on April 26, 2018.

What’s Your Game Plan? K r i s t y C a r t e r , P a t h wa ys I n t e r n

The days are getting slightly shorter. Tem-

peratures a little cooler. School is back in

session. What else does that mean? Football

season is back! With tailgate season upon

us, it’s important to discuss your severe

weather game plan with your friends, fami-

ly, or fellow tailgaters before heading out to

your favorite tailgate spot or pre-game ac-

tivity since severe weather in Iowa is possi-

ble most of the year. Do you know what the

university, high school, or professional foot-

ball action plan is in the event of severe

weather? Where should you go from the

parking lot if severe weather were to occur

before heading into the stadium?

Tailgaters and tailgating activities can be

vulnerable to lightning, high winds (flying

debris), and heavy rain/flooding. Having a

game plan before the big game could save

your life if severe weather were to strike.

Here are some tips to add to your tailgate

preparations on game day:

Remain weather aware. Check the fore-

cast. Look before departing the house even

if you looked at the forecast earlier in the

week, or the night before, they can change!

Get a good weather app that can provide

weather warnings if needed.

Have a backup way to get those weather

warnings. Phone batteries can die. Consider

a portable NOAA weather radio.

Postpone tailgate activities if you hear

thunder. Return to your vehicle or get to a

sturdy building. Avoid metal objects and

water (puddles), as both are conductors for

electricity.

Heed all NWS warnings. On/near

bleachers, under trees, in a tent, or out in an

open parking lot are all not safe places to be

in thunderstorms, even if you can’t see the

lightning!

Don’t forget about the heat and its poten-

tial effects on your body! (Same with the

cold!)

Severe weather policies and action plans

vary by university, school district, and or-

ganization, so check with your team or tail-

gating location of choice for specifics to stay

safe during your next tailgate. Enjoy the

game!

Fire Weather Season Begins This Month! F r a n k B o k s a , M e t e o r o l o g i s t

The fall fire weather season for central Iowa

typically begins in mid to late September…

once the corn and soybean crops begin their

curing process. In central Iowa we experi-

ence two peaks in the fire weather season.

Each peak has their own threats. In the

spring, when grasses go from dry and

dormant to green, and Iowans are cleaning

areas from yard litter and burning the litter

in ditches when the weather can rapidly

warm and dry out (low humidity), the fire

threat comes from strong southerly winds

carrying embers from the ditches into dry

and mostly cured grass stands.

In the fall, the threat is very different and

actually has two phases. Beginning in Sep-

tember, crops dry and if we get warm and

windy days once crops are dry fires can

quickly spread. The threat early on comes

from farm equipment working it the fields

to harvest crops. Hot machinery can start

corn and bean stubble on fire and the wind

can carry these embers into standing crop

areas and adjacent grasslands. Fires can

quickly grow out of control and become a

danger. We would like to make the farming

community aware of our Grassland and

Crop Fire Danger maps issued in the fall

season to give a heads up to potential dan-

ger. If your area is in a very high or extreme

fire danger, please consider harvesting

when winds are light and humidity levels

are above 25 percent. This information can

be ascertained from our fire weather

webpage at: https://www.weather.gov/

dmx/fire

Towards the end of harvest through Novem-

ber, camping and warm season grass dry

down become the main danger. Be cogni-

zant of the conditions around you and the

dangers of campfires and dry conditions.

Make sure fires are completely extinguished

before leaving them and don’t discard lit

cigarettes and other smoking material into

an open area. Place them in a burn proof

container.

Eugene McAlexander (top left photo) of Beaconsfield, Iowa and Nicky Lenz (top center photo) of Boyer, Iowa were recently honored

for 30 years of service as volunteer observers for the National Weather Service. As observers, Eugene and Nicky send in daily tem-

perature and precipitation measurements, valuable in forecast verification and understanding the local climate. Eugene also re-

cently celebrated is 95th birthday—Happy Birthday, Eugene!

Interim General Manager Shawn Dietz (holding plaque in bottom left photo) receives a 25-year Institutional Length of Service

award on behalf of KLMJ Radio in Hampton, Iowa. Brad Fillbach (left in bottom left photo) presented the award. The NWS has

many institutions like KLMJ Radio that take daily temperatures and precipitation observations for several years.

Bretty Murley of Sac City, Iowa (top right photo) and Meg Beshey (holding award in bottom right photo) both received their 10-year

Length of Service award. Pictured with Meg is Brad (left) and Jeff Johnson, Meteorologist-In-Charge at NWS Des Moines (right).

Weather.gov/desmoines

Editor E-mail:

Kenneth.Podrazik@noaa.gov

Brooke.Hagenoff@noaa.gov

9607 NW Beaver Drive

Johnston, Iowa 50131

Phone: 515-270-2614

Cooperative Observers Honored for Their Years of Service B r a d F i l l b a c h , O b s e r va t i o n P r o g r a m L e a d e r