Red Flag Warning issued for all of Western Washington

Red Flag Warning issued for all of Western Washington »Play Video
A brush fire burns along SR-3 near Shelton on Aug. 17, 2012.

SEATTLE -- As Western Washington waded through a last day of 90 degree weather Friday, attention now turns to a new weather threat that looms for the weekend: a dangerous combination of lighting and super-dry conditions.

The National Weather Service has issued a Red Flag Warning for critical fire conditions for all of Western Washington from essentially midday Saturday through Sunday morning.

The warning even includes the Puget Sound metro and other lowland areas that are rarely given such warnings.

A Red Flag Warning means that conditions are already conducive for fires to easily begin and if a brush fire or wildfire were to be started -- be it caused by humans or lightning, that a combination of strong winds, low humidity and warm temperatures will create explosive fire growth potential.

Seattle hasn't seen measurable rain since July 22 -- a period of 26 days -- and hasn't seen significant rain since July 20. The past week's stretch of temperatures in the 80s and 90s with low humidity has only dried out everything further.

And as if to illustrate how dry it is, a brush fire broke out about 5 miles north of Shelton along Highway 3. Firefighters and a helicopter were working to douse the blaze. There is no word what started it.

Outdoor burn bans remain in effect for much of Western Washington, including King, Snohomish, Pierce, Kitsap and Thurston County.

Thunderstorms are expected to move through the region Saturday, first starting on the coast and Olympics in the morning, then spreading into the Puget Sound and inland areas in the afternoon through the night, courtesy of a low pressure center that will drift by just offshore.

The first inkling that it's happening will be an increase in the humidity Friday night into Saturday as the flow veers from the east to from the south and picks up some moist air.

As the low approaches and moves through, it will destabilize the atmosphere and add moisture and lift to the tremendous amount of heat energy already in place.

It's a recipe for towering thunderstorms with frequent lightning and therein lies the concern since any spark from lightning could touch off a wildfire. Highs will still remain quite warm -- in the low-mid 80s and as we mentioned, it'll be quite muggy. So not a very comfortable day Saturday either.

If you'll be outside just be sure to keep an eye to the south for any approaching storms and move inside if they approach. These storms have potential for quite a bit of lightning, if not much rain (these are more the desert-type mainly dry thunderstorms).

The thunderstorms will move off to the north by dawn Sunday and the rest of the day should feature calmer conditions with just some marine clouds giving way to sunshine. No additional thunderstorm threats are foreseen through the rest of next week.