SPOT WEATHE FORECAST

12/12/2008 Weather Discussion: Today’s winter storm is right on schedule with snow currently falling at the Pass. The snow should intensify through the night. Cold air will then push in from the northern interior bringing cold dry weather to the PNW by Sunday. Long-term models show snow showers lingering in the mountains through Sunday. Cold dry arctic air will then settle over PNW for a very chilly week ahead. Forecast from Friday 4pm to Saturday 4am Precipitation .75 -1 in. Water 10 -14” in. Snow Temperatures Low 20 High 26 Winds 5-15 W Gusty Forecast for Saturday 4am to 4pm Precipitation .25 in. Water 2-4 in. Snow Temperatures Low 10 High 20 Winds 0-10 NE TRENDS AND TIMING Precipitation: Snow will intensify through the day. A Puget Sound convergence will enhance *orographics this evening. Snow will begin to taper after 10am tomorrow. Storm totals will depend where the center of the low tracks. (which the models disagree on) If the center tracks north of Stevens Pass we could see 2 feet of snow by the end of tomorrow, but if it tracks directly over us then we will get less accumulation. For now storm totals are calculating out to be 12 -16”. A weak showery pattern will persist through Sunday which could provide a few more inches of very cold dry snow. Freezing levels: Freezing levels will trend down from 3500’ to 2000’ by 4am tomorrow. Then freezing levels will continue to drop reaching sea level later in the day. Cold NE air will follow in late Saturday night bringing single digit temps for Sunday. Winds: There is still a question whether the high winds will affect the center of the state – they seem to be targeting the coast and the southern lowlands. The best chance of high winds will be during the convergence period this evening. Wind will shift to NE during the day tomorrow. *Weather fun fact: orographics – how weather is influenced by the mountains. As air moves into mountains it has to rise right. Rising air cools, moisture condenses, and you get rain or snow. This is the best set up for squeezing the maximum amount of moisture out of an air mass.