National Weather Service National Oceanic and Atmospheric Administration Weather Forecast Office Portland, OR Thursday, Mar 23, 2023
Late season winter weather is expected through the weekend with widespread probability for snow. Snow levels will begin to lower with the onset of colder air tonight. By Friday morning they will reach around 500-1000 ft where they will hover through Sunday. With this system expecting widespread precipitation over all of southwest Washington and northwest Oregon. Moderate to heavy at times heavy snow is forecast over the Cascades where we have the highest confidence. There is around a 90% chance of exceeding 12 inches of snow through Friday (period of heaviest snow) with the highest amounts along the Central Cascades and Lane County Cascades. There is around a 35-45% chance of seeing greater than 18 inches of snow during this time frame. Snow will persist through Sunday becoming lighter over time. The Coast Range too will see increasing snow amounts with greater than a 90% chance of seeing 6 inches or more tonight into Friday, and even higher amounts on elevations above 1500 ft. Lowland snow chance for greater than 1 inch remains around 20-25% by early Saturday morning. Thunderstorm chances remain each afternoon with small hail /graupel possible. If rates are high enough, may see accumulating hail along roadways. Note that below will refer to moderate winter related impacts. This means that there may be disruptions to daily life with some travel impacts.
KEY POINTS
• Snow levels will range from about 500′-1500′ Thursday night through Sunday afternoon, lowest in the early morning and highest in the late afternoon.
• The highest probability for low-elevation snow is late Thursday night / Friday morning and again Friday night /Saturday morning.
• The probability for 1″ or more of snow below 500′ is 10-20% Thursday night / Friday morning and 20%-30% Friday night / Saturday morning.
• Intense showers could bring bursts of hail and graupel Friday afternoon. The probability for hail or graupel to briefly accumulate on roads at any one location is ~10%.
• The Cascades will have heavy snow above 2500′ Thursday, with snow showers and continued accumulation Friday and Saturday.
• 80% chance of moderate winter related impacts to the Cascades above 2500 ft through Friday morning. Less than a 30% chance of moderate winter related impacts to lowland valley locations through Friday morning..
CHANGES FROM PREVIOUS BRIEFING
• Winter Storm Warnings in effect for the following locations: The Coast Range including the Willipa Hills, and the Cascades and associated foothills.
• Slightly higher storm total snowfall over the Cascades with up to 25 inches at around 3500-4500 ft and up to 30 inches along the peaks.
• Moderate snowfall will persist through early Friday afternoon over the Cascades with the warning persisting through early Saturday afternoon.
• Increased chances to 25% for lowland snow below 500 ft Friday night into Saturday morning, with lowered probability on Thursday night into Friday morning.
CHECK TILLAMOOK COUNTY EMERGENCY MANAGMENT’S FACEBOOK PAGE FOR UPDATES DURING THE STORM
