Effective on March 8, 2023, at 1:00 PM Pacific Standard Time (PST), 21:00 Coordinated Universal Time (UTC), the NWS Weather Forecast Office in Pendleton, OR (PDT) will complete changes to Public Weather Forecast Zones encompassing the Washington counties of Kittitas, Yakima, and Klickitat. After this change, all public forecasts and related products will use the new zone numbers and names shown below. 

If March 8, 2023 is declared a Critical Weather Day, this implementation will be postponed to March 9, 2023 at 21:00 UTC.

These changes are intended to provide increased specificity, enhanced representativeness, and improved accuracy of forecast, watch, warning, and advisory products in the Public Weather Program. 

Service Change Notice

Why is NWS Pendleton Changing this Forecast Zone?

NWS Pendleton will be converting the Washington Public Forecast Zone 520, East Slopes of the Washington Cascades, into two (2) separate zones. This change will allow differences in climatology to properly be addressed while better reflecting the influences of complex terrain that can result in weather changing significantly over short distances. The public forecast zone will be divided roughly north to south into two zones. The westernmost zone will become a new zone named “Upper Slopes of the Eastern Washington Cascade Crest” and the easternmost zone will become a new zone named “Lower Slopes of the Eastern Washington Cascade Crest.”

Key Points:

1. This change will better support our Impact-based Decision Support Services and watches, warnings, and advisories by using two public forecast zones to address climatological differences in seasonal snowfall. Currently, winter weather watches, warnings, and advisories are disseminated often for too large an area when the threat is primarily confined to the Cascade crest and the immediate area east over the upper slopes. This characteristic has been identified both internally and by partners. The split will promote more representativeness in our winter weather products.
    
2. This change will improve our messaging through increased specificity that could be attributable to the large changes in elevation over short distances in the original zone and its size. The original zone contains multiple critical transportation corridors (I-90, US-12, US-97, and SR 410), mountain passes (Snoqualmie Pass, White Pass, and Blewett Pass), and numerous towns and communities.

Additional Information

Table 1: Universal Geographic Codes (UGC): Current Public Zone Forecast Name
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WAZ520: East Slopes of the Washington Cascades

Table 2: UGC: New Public Zone Forecast Name
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WAZ522: Upper Slopes of the Eastern Washington Cascade Crest
WAZ523: Lower Slopes of the Eastern Washington Cascade Crest
 

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

For more information or for comments, please contact us via email at w-pdt.webmaster@noaa.gov or (541) 276-7832.