Thursday, May 14, 2015
The wet and cool long-range forecast I’ve been talking about since mid April looks to continue through at least the end of the month as Pacific energy continues to enter the West Coast and tap, to varying degrees. the cold air over the central Canadian plains.
In the short-term, and similar to last weekend, a large and complex storm currently along the West Coast will keep the current unsettled weather going through the weekend. Showers will begin around mid-afternoon today and intensify for a period this evening before briefly ending around midnight.
However, continued pieces of energy ejecting from this storm as it moves eastward will reinvigorate the showers by Friday morning, and keep them going through the day and into the overnight hours. Additionally, temperatures will be cool as the storm approaches the area.
Some energy entering the West Coast around southern California on Friday will lead to a partially split system that first decreases or even ends the rain over our area for Saturday morning. But showers will again increase later in the day as the southern part of the split storm moves first south and then east of our area by Saturday afternoon.
The northern portion of the split will pass mostly to our north, though a lobe of energy looks to pass over our area around Sunday morning, bringing significantly colder air to the region during the day. While the system is not as cold as last weekend, snow levels will eventually fall to around 8000′ with snowflakes again a possibility in the valley during the day Sunday and overnight.
The northern and southern portions of this split recombine to our northeast by later in the day Sunday, dragging the coldest air of this storm over our area by Monday morning and leading to the lowest snow levels of the event overnight Sunday.
Precipitation will only briefly end as another Pacific storm crosses the West Coast on Monday and increases showers again by Monday afternoon. These showers will only intensify as energy is ejected from this new storm, and will turn into more persistent rain later Tuesday as the storm crosses over the area.
Conditions will finally moderate for a short time midweek, though afternoon storms are likely with lots of moisture hanging around after the two storms.
Yet another storm will threaten Memorial Day weekend, though the forecast for then is uncertain as the American GFS takes a lead shortwave across the area near the end of the workweek before bringing a much stronger storm across the West Coast by late in the weekend, with relatively drier weather in between. The European ECMWF has these two waves moving across more coherently earlier in the weekend leading to a wetter forecast.