WeatherWatcher: Our slight chance of thunderstorms has become more likely for Saturday night

Lightning over Bellevue from Log Boom Park July 3, 2008
Photo by Carl Dinse

This Saturday morning's slight chance of thunderstorms verified, even though as late as Friday night the forecasts were leaning towards this system staying east of the Cascades. We got quite the impressive show of lightning and thunder.

The National Weather Service in Seattle even issued a severe thunderstorm warning for Shoreline Saturday morning at 8:15am, in effect until 8:45am with dime sized hail possible. The last time a severe thunderstorm warning was issued for Shoreline, I believe, was August 2006 when we had urban flash floods caused by a daytime thunderstorm cell.

The cloud tops for these thunderstorm cells reached as high as 45,000 feet, which is what prompted the large hail warning. Lightning was reported hitting a tree in Kirkland, knocking picture frames off walls of nearby houses and sending wood debris as far as a block away from the damaged tree.

Round 2 is now expected: Radar indicates another band of heavy showers moving through the area between 2pm and 3pm, but it does not appear any lightning is currently associated with this band. We should have a good break from the rain after 3pm or 4pm; we might even see some sunny skies for a couple hours late in the afternoon and early evening.

Our next band of possible thunderstorms moves in from Oregon sometime between 7pm and 10pm. The peak of it should be over Shoreline around 9pm, according to the recent high resolution forecast models. Forecasters are still calling for a slight chance of lightning, but we are expecting heavy rain at times. We could receive up to 1 inch of new rainfall this evening.

Severe thunderstorms are expected over the Cascade mountains, and Eastern Washington could see super cell development.  The National Weather Service even has severe thunderstorm watches and flash flood watches in effect for Eastern Washington. It is very likely we will at least be able to see some of the lightning from the Cascade mountains, especially if you have a good view looking east.

Our slight chance comes in play as we can't rule out some of those Cascade thunderstorms drifting west over the Puget Sound Lowlands, or if some of the heavier rain showers get a good electrostatic charge going.

For current weather conditions visit www.shorelineweather.com