WeatherWatcher: Weekly Report, A storm, snow, then very cold

• Forecast
• December cold
• Last week's data

Forecast

Sunday - We have some heavy rain moving into the area. It looks like Shoreline and Lake Forest Park will be on the southern fringe of the Olympic Mountain rain shadow so we may not be as wet as most places in the Puget Sound region. It will be breezy at times as well, however we are not expecting anything major to cause widespread power outages. 

Monday - Rain showers in the morning may turn into snow showers in the afternoon and evening. For the most part it is expected to dry out by the time the really cold air arrives from the north.

However, there are a couple of wild cards in the mix. One situation is that there will be a Puget Sound convergence band that may develop, anywhere north of Seattle. It could form over Shoreline-Lake Forest Park or it could be further north. Also it could easily slowly move from north to south or south to north, depending on where it forms. Another wild card is that the leading edge of the cold air could generate a local "cold front" which would force a small band of showers to move from north to south leaving a light accumulation. Of course if both wild cards happen it could make things a little more interesting. In general though this is not looking like it will be a major event but it is possibly going to make the evening commute a disaster.

Bottom Line: I strongly urge everyone to prepare for winter driving conditions before leaving for work Monday, even if it's warm and raining Monday morning. This cold air moving in is going to be the coldest air mass we've had in the region in 2 years. It will cause a sharp temperature drop through the afternoon and evening.

Tuesday-Saturday: We will be back into another blocking high pressure dry pattern, but it will be very cold. Most of the week temperatures in our area will struggle to reach above the freezing mark. We will have low temperatures in the 20's, and we could see the teens mid-week.

Next weekend is still far enough away to be somewhat uncertain, but early indicators are pointing to another possible snow event. This may be interrupted by Sunday or Monday with a slight warmup to rain, before yet another cool down to below freezing is possible.

December Cold: Longer range forecasts on multiple sites seem to agree that our December will be anywhere from 2-8°F colder than normal. There is strong hints that ridging well off the Pacific Coast stretching to Alaska will force storms to go up and over the Arctic bringing storms and cold down along the west coast. We may be a lot drier than normal for December due to the ridging so I'm not expecting significant snow accumulations but I'm pretty sure we will have a couple of snow events. Most of our precipitation in December, might fall as snow, instead of rain in general. 

Average daily temperature for November 2013.
Graphs by Carl Dinse

Average Daily Barometer (inHg) November 2013.
Graphs by Carl Dinse

Last week's data:

High temperature: 51.8°F (Wednesday)

Low temperature: 30.7°F (Saturday)

No rainfall last week.

Warmest day: 43.9°F (Wednesday)

Coldest day: 37.5°F (Saturday)

Average temperature last week: 40.3°F (3.1°F colder than normal.)

Station historic average temperature: 43.4°F

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