WeatherWatcher: Special report, winter storm watch issued

• Forecast
• Winter Storm Watch
• Graphs and Highlights

Forecast: Cold air has begun moving in Wednesday evening and will continue to move into the region during Thursday and Thursday night under clear skies. We have a wet but warm storm moving in from the Pacific overnight Thursday into Friday morning. Air is expected to be below freezing when the precipitation from this storm moves over our area overnight into Friday morning. Snow accumulations are likely from 1-4 inches in Shoreline and Lake Forest Park before turning over to rain in the afternoon hours. Warmer air moves in Friday afternoon and over the weekend bringing temperatures back into the mid-upper 40's for a high. Expect a series of weather systems to move through to keep us wet off and on through the weekend and early next week.

Winter Storm Watch: The National Weather Service in Seattle has issued a winter storm watch including the areas of Shoreline and Lake Forest Park. The watch is in effect from Thursday evening until Friday afternoon. As this next storm moves in overnight Thursday, widespread snow is expected to develop across the entire Puget Sound region. We are right on the fringe of accumulation totals from 1-2, to 2-4 inches, so I suspect the exact alignment of the storm will be key for how much snow Shoreline and Lake Forest Park might get before it warms up to rain. The further north you are, the more snow is likely on the ground.

Worst case scenario, we could receive up to 5, maybe 6 inches of snow. More is possible if the changeover to rain does not happen when expected.

Likely to happen, and what I think will happen, is we will probably get 2-3 inches of snow before a changeover late morning. It will be just enough to make the morning commute difficult; however the drive home should be clear and unfrozen. This event will have help sticking to roads and urban areas due to the very recent deep freeze we just had. This is because most lakes, rivers and creeks now have cooled down to just above the freezing mark and no longer provide the extra moderating effect that usually takes place during an early season snow event. Many freshwater bodies around here have already frozen at least partially earlier this month.

Be prepared for winter driving conditions if you will be heading out in the overnight or early morning hours Thursday night and Friday morning.

Below are some graphs from the data so far this month. We have had a very cold and dry December. Usually we are warm and dry, or cold and wet, but not this winter so far. What was amazing was the very low dew points we had during the cold snap. One day we had a dew point as low as -6.6°F! Coldest temperatures recorded this month, Saturday December 7th: 15.8°F, Sunday December 8th: 14.5°F, and Monday December 9th: 18.1°F. We stayed below freezing from December 4th, Wednesday afternoon until December 10th, Tuesday afternoon, (6 days total). 

Daily Average Temperature December 2013
Graphs by Carl Dinse

Daily Average Dew Point December 2013
Graphs by Carl Dinse

Daily Average Barometer December 2013
Graphs by Carl Dinse

For winter storm updates and current weather conditions, check out my web page www.shorelineweather.com.