WeatherWatcher: Winter Weather Advisory, Forecast, December graphs

The National Weather Service in Seattle has changed the Winter Storm Watch to a Winter Weather Advisory in effect from 4pm Thursday evening until 8am Friday morning. A winter weather advisory is issued when winter weather is expected to mainly affect roadway surface conditions, causing travel difficulties.

In general we have a Pacific storm moving in from south to north. The air will remain below freezing, with snow expected to arrive from the south in the Shoreline area at about 7pm. Current models are suggesting a modest accumulation of 1-3 inches, with a changeover to rain not occurring until mid Friday morning or afternoon.

I want to stress that all of the forecast models have not been consistent with this development at all. There's a very good chance we might not see any accumulation. On the other hand there is also a chance that we could see more than a 3 inch accumulation. As you can imagine, the past few days has been very challenging for forecasters.

Bottom line: Be prepared for winter driving conditions if you will be traveling after 6pm Thursday and before 8am Friday morning. Changes in this event and the way it might turn out can occur at any point during or after the winter weather advisory period. I will be posting updates if significant changes occur.

Weekend forecast: Most models (not all) indicate a slight warm up to upper 30's and low 40's with rain and rain showers through the weekend. Temperatures will be on the cool side, and some models indicate that we may bump into the freezing mark at least in the overnight lows into early next week. Though not likely, some wet snow flakes might be a possibility still, especially if a convergence does form from a passing storm front.

There are still some hints that we might go into another modified arctic freeze off and on for the next week or two so I wouldn't put away the winter gear just yet after this storm.

Below is the rainfall and temperature data for this month so far. We're actually running near normal for temperature, if not slightly below normal right now. Rainfall is a little under the average at the moment but this is typical when we get a cold outbreak.

Daily rainfall for December 2016 compared to station average.

Daily High and Low temperatures for December 2016 compared to station average.

For current weather conditions here in Shoreline, visit www.shorelineweather.com