November 10 t h Northern Iowa Ice B r o o k e H a g e n h o f f , M e t e o r o l o g i s t

The Weather Whisper December 2020

May 2019 NWS Des Moines

Cover Photo:

Ice-coated grass, power lines, and

street signs in Fonda, IA on

November 10th.

Courtesy @Fonda_IA via twitter.

On the morning of November 10th, many across northern Iowa awoke to a coating of ice across trees, power lines, and fences. This coating of ice caused power outages and tree damage for some, but what made this event unique was the relatively minor impact to roads. While a few slick spots did develop by mid to late morning, most roads remained wet with little to no ice accumulation at all.

Forecasting the event was a challenge in and of itself with portions of the state receiving snow while others saw freezing rain and still other received only rain. Systems such as this that involve multiple types of precipitation—rain, freezing rain, snow, etc.—can be partic-ularly difficult to forecast as a single degree can make a big differ-ence in what kind of precipitation falls and how much of it accumu-lates. This can be further complicated by warm ground tempera-tures, which may result in accumulations on elevated surfaces but not on roadways—as was seen in this case. But temperatures at the surface are only half the story. For the full story, we need to examine temperatures through a deep layer of the atmosphere. Warm layers above the surface determine what kind of precipitation will reach the ground, and even small changes in these temperatures can have a big impact on the weather we experience at the surface.

B

A

C

Ice covered trees in Fonda, IA.

Courtesy @Fonda_IA via twitter.

Descriptions of graphics to the right

A. Precipitation falls as snow when the temperature remains at or below 0 degrees

Celsius (32°F) from the cloud base to the ground.

B. Sleet falls when snowflakes partially melt as they fall, and then refreeze before

they reach the ground.

C. Freezing rain falls when snowflakes melt completely before reaching the surface,

and refreeze upon contact with anything that is at or below 0 degrees C (32°F).

Graphics courtesy of NSSL—click to view larger

Weather.gov/desmoines

Editor E-mail:

Kenneth.Podrazik@noaa.gov

Brooke.Hagenhoff@noaa.gov

9607 NW Beaver Drive

Johnston, Iowa 50131

Phone: 515-270-2614

Partner and Public Feedback Wanted!

The National Weather Service is conducting a national survey to solicit

feedback from partners and the public on how they receive and use frost

and freeze information. Currently, the NWS issues five products to alert the

public and partners on these hazards: Frost Advisory, Freeze Watch, Freeze

Warning, Hard Freeze Watch, and Hard Freeze Warning. No changes are

being proposed at this time, but the NWS will use information gathered

during this public comment period to inform future plans.

Click the image to take the survey!

Christmas Climatology for Waterloo and Des Moines K e n n y P o d r a z i k , M e t e o r o l o g i s t

The Iowa Department of Transportation, Iowa

Department of Public Safety/Iowa State Patrol, and

the National Weather Service partnered together to

produce an hour long winter resources webinar for

members of the media on the Friday before

Thanksgiving. Each agency presented how their

respective offices prepare for winter operations and

ways to communicate with them during winter

weather. The three agencies also provided specific

winter safety tips and various statistics related to

winter storms (like the image to the left) and winter-

related incidents. Remember, you can find the latest

road conditions at 511ia.org and the latest forecast at

weather.gov.

The webinar was well received by the media across

the state of Iowa. Thank you to the Iowa DOT and

Iowa DPS for their great partnership as well as to all

media for joining the webinar. We hope you all have a

safe winter weather season.

Joint Winter Preparedness and Resources Media Webinar K e n n y P o d r a z i k , M e t e o r o l o g i s t