Seasonal weather change arrives with potential for heavy rain in the forecast

WHATCOM COUNTY, Wash. — Days of 70-plus high temperatures appear to be coming to an end this year according to the latest weather forecasts.

A moderate weather system expected to bring light rain to the lowlands and up to a half-inch in the Cascades is expected to arrive over Whatcom County and much of western Washington late today, September 19th.

Precipation forecast for Whatcom County lowlands as of Tuesday, September 19th. Source: meteoblue

As detailed in the graph above, a stronger weather system is currently forecast to arrive Sunday that will bring several days of moderate to heavy rain to the Whatcom County lowlands. As is normal, heavier rain is expected in the Cascades.

Plot of vertically integrated water vapor analysis forecast for September 25, 2023, as of September 19th based on ECMWF forecast model. Source: Center for Western Weather and Water Extremes

The image above shows a forecast showing the September 25th position of an atmospheric river expected to deliver significant precipitation to the Pacific Northwest region.

Click for more information

Nooksack River level forecasts reflect increases due to the expected rain but do not show river levels near flood stage.

Whatcom News readers are encouraged to stay up to date with current weather alerts and forecasts and air quality readings for their specific Whatcom County locations along with tide tables via the Whatcom News Weather page.