The following is a significant weather briefing highlighting possible weather conditions for Western Washington, Christmas Day, Tuesday December 25, 2012.
Current Weather Forecast from the National Weather Service is here: http://tinyurl.com/d45ylov
Current Weather Forecast from the National Weather Service is here: http://tinyurl.com/d45ylov
IMPACTS:
· Lowland snow expected across much of Western Washington Christmas day. Snow accumulations could be significant over the Kitsap peninsula (including Hood Canal), the Lower Chehalis Valley (East of Aberdeen), and the remaining Southwest Interior. Only light or insignificant snow accumulation elsewhere including the urban corridor from Pierce county (including Tacoma) Northward to Whatcom County (including Bellingham), the Strait of Juan De Fuca, and near the Washington Coast.
· Mountain snow including all passes. Snowfall amounts of 4 to 8 inches expected in the Olympics and North Cascades with 5 to 10 inches in the Central Cascades.
· Locally Strong wind. The East Puget Sound lowlands along the Cascade Foothills could get East winds of 25 to 35 mph with gusts to 50 mph.
· The threat of lowland snow will diminish for most areas by late afternoon as precipitation changes to rain. Areas along the Hood Canal could still have enough cold air trapped so that snow accumulations continue into the evening. By late evening, expect snow to become showery with little additional accumulation.
SUMMARY:
A front will approach the area Christmas Eve. There will be a break in showers and a period of partial clearing overnight which will allow temperatures across Western Washington to fall to near or just above freezing.
The most up to date information indicates precipitation will reach the coast around 4 AM Christmas morning and spread into areas South and West of Puget Sound through 8 AM.
Precipitation is not expected to begin around Tacoma Northward along the I-5 corridor through Everett and Bellingham until later in the morning. Because the air mass will initially be cold, precipitation is expected to begin as mostly snow across Western Washington. Some areas will change over to rain much quicker than other areas.
Locally heavy snow may fall along Hood Canal and from Western Pierce County Southward. Areas right near the Coast and from Tacoma Northward to Bellingham will also see a trace to locally 2 inches of wet snow before changing over to rain within a few hours after precipitation begins.
PRIMARY AREAS IMPACTED:
Winter Storm Watch: The Kitsap Peninsula including Hood Canal, the Lower Chehalis Valley (East of Aberdeen), and the remaining Southwest Interior:
The heaviest lowland accumulations are anticipated within this area. Snow will begin along the coast around 4 AM Christmas morning and spread into the remainder of the Southwest Interior area by 7 AM. Accumulations of 3 to 5 inches appear likely through early afternoon before a mix or change over to rain prohibits additional accumulation.
Cold air will be particularly stubborn to scour out of Hood Canal. This means precipitation could remain mostly snow through Christmas day into the evening hours. Accumulations of 4 to 8 inches with locally higher amounts are possible until precipitation becomes showery by midnight.
Snow amounts this heavy may cause tree branches to come down causing local power outages. Also, travel in the effected areas could hazardous at times.
Remaining Lowlands from Tacoma and Vicinity North to Bellingham including the Strait of Juan De Fuca and near Washington Coast:
The coast will have snow beginning earlier around 4 AM. A change over to rain should occur within a couple hours. Accumulations on the coast including Forks, Hoquiam, and Aberdeen will likely be a trace to locally 2 inches depending on how quickly the change over occurs.
Snow will begin after 9 AM Christmas morning and probably not until midday across the North Interior. Only a trace to 1 inch of snow is expected before a change over to rain occurs. Local amounts of 2 inches may fall on hilltops. Most snow accumulation will occur on grassy areas or cold surfaces, and on hilltops.
Cascades and Olympics:
Snow will begin first in the Olympics early Christmas morning, then spread to the North and Central Cascades by late morning. Accumulations of 4 to 8 inches are expected in the Olympics and North Cascades, with 5 to 10 inches in the Central Cascades by evening.
Travel through all the passes may be hazardous at times. Snow will taper to showers during the evening hours.
In addition, an avalanche watch is in effect for the Olympics and Cascades Christmas day and evening.
East Puget Sound Lowlands
Strong East winds are expected to develop along the the Cascade Foothills extending to just East of Bellevue Christmas morning. East winds of 25 to 35 mph with gusts to 50 mph are possible. The strongest winds are likely to occur from 6 AM to 2 PM on Christmas day.
FORECAST CONFIDENCE AND UNCERTAINTIES:
Confidence is high that precipitation will begin mostly as snow as it spreads into Western Washington Chistmas Day. It also appears likely that heavy snow defined as 4 inches or more will occur along the Hood Canal and Kitsap peninsula.
There is moderate confidence in snow amounts across the Southwest Interior, Lower Chehalis Gap, and remaining Southwest Interior. Some areas could see a faster change over to rain which would cut back on snow totals. The change to rain could also take a little longer than expected which would likely result in somewhat higher accumulations.
LOOKING AHEAD:
Showers will decrease Christmas night with little or no additional lowland accumulations. Snow showers will produce only minor accumulations in the mountains into Wednesday.
