Winter Weather Potential for Portland Metro January 11-18 2020

NCEP Temperature Probabilities Jan 11-18. Click to enlarge

BBBRRRrrrr!! Starting this weekend, a series of systems will usher in the coldest air we've seen so far this season.

By Garret Hartung (Wilkes East resident)
Climate Science Undergrad, Oregon State University

With this cold air in place next week (Jan 11-18), any system swinging in moisture from the Pacific has the potential to bring winter precipitation to the lowest elevations. In typical Pacific Northwest fashion, this forecast is complicated, so its best to break it down into a few categories: what we do know, what is uncertain, and how can you be prepared.

What We Do Know:

• Temperatures are expected to be well below the average high of 46°F for this time of year. The NCEP (National Centers for Environmental Prediction) is showing an 80% or greater probability of below normal temperatures in our area for next week. High temperatures are looking to be in the low 30’s starting Tuesday with lows in the mid to lower 20’s. It wouldn’t be too shocking to see temperatures dip below 20°F in this set up. There is still some uncertainty in regard to how cold it will get, there are a few models showing temperatures even lower than what was mentioned above but confidence in that is very low
• The east wind should be howling during this period. This is where most of the cold air will come from. Depending on the exact strength and location of a system we could see gusts exceeding 40mph, which is strong but not out of the ordinary for our area. Typically, we see a few 40+mph gusts from the east each year. This could lead to some very cold wind chills, probably getting into the teens or lower for some days.
• The upper level pattern is conductive of storms developing off the coast. For most of next week, temperatures should be cold enough in Portland to support snow at the valley floor. It’s appears fairly certain we should see some precipitation in this period.

What is Uncertain:

• A few models are showing extremely cold temperatures in our area that haven’t been seen in decades. While I wouldn’t bet on that occurring, there is a small possibility that does occur. For example, the latest run of the GFS (Global Forecast System) model has lows in the single digits. While other models keep us in the 20’s/30’s.
• The big question is how much precipitation we will get. Models have been showing anything from nothing to a 2008-like event for the Portland area. There are several factors that are leading to this uncertainty. The main thing is the track and strength of the storms that may or may not form. A stronger storm may produce more precipitation but could also bring in warm air from the south to keep us above freezing. A storm tracking too far north could do the same thing, while a storm tracking too far south may leave us cold but dry. We won’t know the exact strength and track of a storm till about 3 days out. So, any estimates of the amount of snowfall we could get should be questioned until we are with in 36 hours of the event. This was an issue last year when crazy model outputs were being shared on social media, causing some what of a panic. I will say that the models are starting to zero in on Thursday as out potential big snow day, but specific details will change in the coming days.

How to prepare:

• Winterize your home if you haven’t done so yet this winter. In particular shut off and cover outside faucets and make sure the pipes in your home are ready for the coldest temps of the season thus far. If you have a generator for your home, make sure its good on fuel and you know how to connect it properly. Freezing rain is not out of the question for this event, especially for areas exposed to the gorge winds.
• Stock your car on winter survival gear. Have chains or traction tires ready if you need to travel this week. Things like some food, water, kitty litter, and other supplies you may need if your car gets stuck.
• Have a plan. Should we have a high impact winter event, be prepared with food (for you and your pet) and medicine in your home and try not to travel. Think about things you’d need if you can’t leave the house for a couple days. It’s also good to think about potential loss of power. Keep your phone charged and have flashlights ready.
• Be weather ready! Stay informed by paying attention to local media outlets and the National Weather Service for the latest forecasts and warnings. These men and women know the area and know how snow events play out more so than the app on your phone.

The bottom line is that cold weather is expected and all types of winter precipitation including snow and freezing rain could occur next week. So be prepared for impactful weather.

It’s better to prepare for an event and it doesn’t occur than to not be prepared if it does.