New Forecast Zones - Oct. 10th

Effective Tuseday, October 15, 2019, at 1200 PM Mountain Daylight Time, 1800 Coordinated Universal Time (UTC), the NWS WFO in Billings, Montana (WFO BYZ) will change all public forecast zone names and boundaries.  Upon implementation of this change, all public forecasts and related products will use the zone numbers and names shown below.

The zone changes will improve services by allowing more fine-tuned warnings and advisories for hazards such as dust, fog, and winter weather.

Why is NWS Billings Proposing to Change Their Forecast Zones?

In Montana, most long-fused watches, warnings, and advisories issued by the NWS (such as Wind Advisories and Winter Storm Warnings) are issued in areas called “zones”. Our current configuration of 26 forecast zones was created during the mid-1990s using broad-brushed climate areas and has not significantly changed since that time. Over the years, NWS Billings meteorologists have found that our current zone configuration does not adequately reflect important local differences in geography and weather impacts. This sometimes results in "over-warning", where an impact is occurring within the current structure of our zones.

To provide a better service to our community we are working towards changing our zone configuration from 26 zones to 31 zones. These proposed zone changes are based on both climatological data, such as average annual precipitation; known weather, water, and climate impacts; and forecaster experience.

How Will The New Zones Result in a Better Service?

There are numerous examples of how adopting a new forecast zone configuration would be valuable for both our core partners, and the public:

Example 1: The Bighorn Canyon is a popular site for recreationists, and is prone to experience strong winds that funnel through the canyon and exit at Fort Smith, MT. These winds are unique to this specific location and do not occur throughout the remainder of southern Big Horn county, a zone that currently includes the town of Crow Agency and much of the Crow Reservation. A new zone at Bighorn Canyon will allow us to fine tune our services for hazardous winds in this area.

Example 2: East of the Crazy Mountains, and between the Musselshell River to the north and Yellowstone River to the south, exists an area of higher elevations that sees much more snowfall than the surrounding valleys. Highway 191 passes through this region, which includes the town of Melville, and can be impacted by significant snowfall. A new zone at the Melville Foothills will enable us to issue winter highlights for this specific area, without the mention of the Harlowton and Big Timber, two towns that lie in the lower river valleys and typically receive much less snowfall.

Proposed New Forecast Zones for October 10th, 2019

Full Resolution 

Current Forecast Zones (Pre-October 10th, 2019)
 

Full Resolution

Additional Information

Updated public zone shapefiles are available for download via the NWS GIS Portal. 

For more information or for comments, please contact us via e-mail or 406-652-0851