‘Bomb cyclone’ over Pacific will target drought-stricken Washington, Oregon

Much needed moisture arrives for the weekend, with a series of storms bring rain to the Northwest.
KENNEWICK, Wash. — After a fairly mild start to the month, big changes are coming for the second half of October. Breezy winds and widespread rain are on the way to finish the week.

VIDEO FORECAST: Very wet Thursday night into Tuesday

It will start to feel more like fall as multiple systems track across the Pacific Northwest, bringing some showers to the Tri-Cities and Yakima Valley as early as Wednesday morning.
Ecmwf Mslp Uv850 Namer 6
After a dry/warm Thursday forecast, heavy mountain rain and snow are more likely by the upcoming weekend. The First Alert Weather Team meteorologists say they are keeping their eyes on a strengthening low pressure system over the northern Pacific Wednesday morning. A rapid drop in pressure is known as bombogenesis…hence the name ‘bomb cyclone.’

What is a bomb cyclone?

Bombogenesis, as defined here by NOAA, occurs when “a midlatitude cyclone rapidly intensifies, dropping at least 24 millibars over 24 hours. A millibar measures atmospheric pressure.”

A combination of different weather ingredients can cause bombogensis to happen. This week, computer models are coming into agreement with the timing of a cold air mass over the northern Pacific colliding with warm tropical energy from the western Pacific.  The rapidly strengthening weather system acts a vacuum as the pressure rapidly drops. This incoming system has the potential to bring damaging storms and wind up the entire west coast, with very drought stricken areas benefiting greatly from the extra moisture.


NOAA: Bombogenesis is a popular term that describes a midlatitude cyclone that rapidly intensifies.

The central pressure of the latest incoming storm is forecast to dip to approximately 28 inches of mercury (948 millibars), putting the bomb cyclone at similar intensity levels to hurricanes in the Atlantic. Snow levels will be dropping to 4500-5000 feet in the Cascades on Sunday. This snow line could drop even lower on Monday. Great news for skiers and snowboarders itching for the upcoming ski season.

The First Alert Weather Team will keep an eye on mountain pass travel on Monday morning. It’s still uncertain if another round of snow Monday would impact drivers heading over the main passes or if it will fall as rain (Snoqualmie Pass elevation: 3022′, Stevens Pass: 4,062′, White Pass: 4,501′).

And a reminder: Eastern Washington and Oregon are still under drought conditions from the extremely hot and dry summer of 2021. The Tri-Cities usually receives 5.43″ of annual rainfall by this time in October. The total amount this year is 2.13″…less than half of normal. Bring on the extra moisture!

Us Drought Monitor