WeatherWatcher: Surprise thunderstorm, December graphs, forecast for the week

Monday, December 31, 2018

Radar image December 30, at 1:45AM PST.
National Weather Service in Seattle

Sunday morning we had a surprise thunderstorm develop through Shoreline and Lake Forest Park.

It produced a nice lightning show for residents in the area, as well as causing brief power outages 3-10 seconds long in some neighborhoods.

This thunderstorm was the result of an active convergence zone behind the cold front of Saturday's windy storm. There was heavy rain, and even hail in areas from this storm. Some of the hail even survived until daylight hours in some spots. Rainfall totals at both Richmond Beach and North Ridge were 0.15 inches from the thunderstorm.

December graphs: December had a quiet start, continuing the weather pattern from November before turning active December 9. We came out just slightly above normal in total rainfall for the month, with several rain events, and wind events. We averaged around 3.6°F warmer than normal for the month as well.

December 2018 rainfall at the North Ridge station.

We had three wind storms, on December 14, 20, and 29. The first windstorm only received a wind advisory by the National Weather Service. This storm did the most damage as it was the first significant windstorm of the season, clocking in a peak wind gust of 43 mph.

Our second windstorm was the strongest, and prompted a high wind warning from the National Weather Service, clocking a peak wind gust of 46 mph. The third storm on December 29 earned a wind advisory which ended up being canceled shortly after the high winds peaked at 35 mph. The third storm just didn't quite get as strong as forecast models predicted.

Daily wind gusts at the Richmond Beach Station for December 2018.

The temperature graph shows the story of our above average temperatures for the month. We had several atmospheric river type storms keeping us warm with tropical and sub tropical moisture.

Daily high and low temperatures compared to station average December 2018, Northridge station.

Forecast: New Year's Eve and New Year's Day a cold start in the morning with temperatures in the low 30's or upper 20's. Areas of fog are likely as well, with a high temperature slightly above 40°F.

Our next weather system starts to approach the area Tuesday evening with increasing clouds and lows near 30°F.

Wednesday afternoon the threat of rain returns with temperatures in the 40's. Winds are expected to be on the increase as well Wednesday night through Friday. Some forecast models are hinting at another wind storm Thursday or Friday. Rain remains in the forecast Thursday through next weekend. High temperatures near 50°F with lows in the upper 30's to low 40's.

I'm still looking for photos and info on past weather events in the Shoreline and Lake Forest Park areas. If you'd like to share your stories and photos please send me an email at

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