La Niña Impacts 

and Outlook

Missouri Basin Region

October 2020

Typical La Niña Winter Pattern

Highlights for the Basin

A La Niña develops when sea surface 

temperatures in the eastern equatorial 

Pacific are consistently cooler than average 

for an extended period of time. These cool 

waters affect the location of jet streams, 

which causes impacts in North America. The 

most notable impacts occur in the winter, 

when the wind patterns in the atmosphere 

are strongest.

While no two La Niña events are alike, 

there are some general patterns that are 

predictable. For instance, the polar jet 

stream is typically farther south than usual 

during La Niña winters. 

For the Missouri Basin states, the typical 

winter La Niña pattern leads to increased 

chances for below-normal temperatures 

across the upper Basin. The northern 

Rockies may also have increased chances for 

an above-normal snowpack.

The image above shows the typical pattern in the winter during La Niña 

events. The polar jet stream tends to traverse right through the Missouri 

Basin, making it the dividing line between cold and warm air masses. This 

means that colder conditions could be in store for areas of the upper Basin,

while the southern Plains could be warm and dry.

Image courtesy of the National Oceanic and Atmospheric Administration.

La Niña Outlook

Winter Temperature and Precipitation Outlooks

Valid for December 2020 - February 2021

Temperature Precipitation

Contact: Natalie Umphlett (numphlett2@unl.edu)

 Doug Kluck (doug.kluck@noaa.gov)

As of mid-October, NOAA's Climate Prediction Center outlooks largely 

follow a typical La Niña pattern for the Missouri Basin states. Generally, 

the region has increased chances for cooler, wetter conditions across 

the north, and warmer, drier conditions across the south. Normal to 

below-normal temperatures are favored in North Dakota and portions of 

Montana, Wyoming, and South Dakota, while normal to above-normal 

temperatures are favored across much of Colorado and Kansas, along 

with southern areas of Wyoming. Normal to below-normal precipitation 

is favored across southern areas of Colorado and Kansas, while normal 

to above-normal precipitation is favored across Montana, North Dakota, 

northern Wyoming, and much of South Dakota.

EC: Equal chances of above, near, or below normal 

A: Above normal, B: Below normal

La Niña Probability

Winter 2020-2021

Missouri Basin Region La Niña Impacts and Outlook | October 2020 

https://www.drought.gov/drought/resources/reports

La Niña conditions have continued this fall 

and forecasts indicate that this La Niña 

will strengthen, peaking as a moderate 

or even strong event in late fall or early 

winter. According to the Climate Prediction 

Center, there is a greater than 85% chance 

that these conditions will last through the 

winter and about a 60% chance that La 

Niña will continue into the early spring, 

as shown in the image above. A La Niña 

Advisory is currently in effect.
Potential Winter and Spring Impacts

Agriculture

Fall harvest in full swing, photo courtesy 

Ken Dewey.

La Niña conditions can have 

worldwide impacts to the agricultural 

sector. In the Missouri Basin, 

widespread drought conditions have 

helped the fall harvest progress 

quickly. However, dry conditions could 

be an issue for winter wheat if timely 

rains do not materialize. Potential 

concerns for the winter include the 

overwintering of pests due to warm 

conditions in southern areas, and 

calving/lambing issues due to cold 

conditions in northern areas.

Missouri River

The Platte River, a tributary of the 

Missouri River, photo courtesy Ken Dewey.

According to the U.S. Army Corps of 

Engineers, after a near-record year 

in 2019, the 2020 runoff forecast for 

the upper Basin was 30.2 MAF, which 

is just above average. Widespread 

drought conditions have impacted 

streamflows and reservoir inflows in 

certain areas this summer and fall. 

Releases from Gavins Point will be 

adjusted upward, as needed, to help 

meet water intake and navigation 

needs downstream. Conditions will be 

monitored throughout the winter.

Economy

Snowy scene in Colorado, photo courtesy 

Bill Sorensen.

Although losses occur regardless of 

ENSO phase, according to insurance 

data, La Niña events tend to result 

in the largest economic losses 

worldwide. For the Missouri Basin, 

impacts could be mixed. For instance, 

northern areas expecting a cold and 

snowy winter could have increased 

costs for heating and snow removal, in 

addition to travel difficulties. However, 

an increased snowpack in the 

northern Rockies could be welcomed 

by ski resorts and outdoor enthusiasts.

Comparisons and Limitations

Winter Conditions During Past La Niña Years

Maps courtesy of the Midwestern Regional Climate Center

The maps above show the winter conditions of the most recent La Niña 

event in 2017-18. Much of the Basin was cooler than average, and, although 

precipitation varied, the highest amounts occurred from Montana through 

central Nebraska. Because no two La Niña events are alike, it is important 

to note that there are limits to the predictability of impacts this winter and 

other factors should be considered.

While past La Niña events can help inform forecasters about certain 

conditions, there are limitations. For instance, in the Missouri Basin, La Niña 

is not known to impact: 1) first freeze in the fall, 2) last freeze in the spring, 3) 

potential for ice storms or blizzards, 4) track or intensity of any single weather 

system, or 5) potential for drought/flooding in the spring.

Missouri Basin Partners

High Plains Regional Climate Center 

www.hprcc.unl.edu

National Drought Mitigation Center 

http://drought.unl.edu/

National Oceanic and Atmospheric 

Administration 

https://www.noaa.gov/

 National Integrated Drought Information 

 System 

 https://www.drought.gov/

 NOAA NCEI 

 www.ncdc.noaa.gov

 NOAA NWS - Central Region 

 www.crh.noaa.gov/crh

 NOAA NWS Climate Prediction Center

 www.cpc.ncep.noaa.gov

 NOAA NWS Missouri Basin River Forecast 

 Center 

 www.crh.noaa.gov/mbrfc 

American Association of State Climatologists 

https://www.stateclimate.org/

U.S. Army Corps of Engineers 

www.usace.army.mil

USDA Northern Plains Climate Hub 

www.climatehubs.oce.usda.gov

Contact: Natalie Umphlett (numphlett2@unl.edu)

 Doug Kluck (doug.kluck@noaa.gov)

Missouri Basin Region La Niña Impacts and Outlook | October 2020 

https://www.drought.gov/drought/resources/reports