LONG RANGE FORECAST THROUGH THE MIDDLE OF JANUARY - 1/3/2019
January is the first full month of winter. There can be days and days of uninterrupted rainfall. Temps will usually be very cold with average highs in the 40s west of the Cascades and 30s east of the Cascades. January here can also feature days of surprising warmth with record highs near 70 west of the Cascades by the end of the month. What will typically be seen are daytime highs ranging from the 30s to the lower 50s. Rainfall is usually substantial at 2 - 6 inches west of the Cascades depending on where you are. Snow can pile up in the mountains as well. Typically above 4000 feet. Of course just two years ago we saw that huge snowfall hit on January 3rd in which nearly a foot to 4 and a half feet of snow fell in Southern Oregon. We also have had Januaries happen with little if any snowfall. At those times, we can see persistent valley fog set up.
January this year has taken some real turns over the last week. At one point it looked like we would be dry with persistent fog in the valleys and sunny and warm elsewhere. But, that has gone right out the window. We expect that the first half of January is going to be very active with rain, snow, and wind expected through the first part of the month. The long range data now shows that we will see above average chances for rain and mountain snow. Temps are also expected to be somewhat above average. This means we would be 5 degrees or so above where we would expect to see them. This means lots of mid to upper 40s west of the Cascades, low to mid 50s at the coast, and mid to upper 30s east of the Cascades.
Seeing wetter than normal conditions is exactly what we need right now. 2018 was a very dry year. Getting off to a good start in january would be a great thing. And, for what we see in the data, we could see rainfall amounts that would be an average January monthly total reached before we get to the end of the month. That is certainly going to be true of this first major storm set poised to come in on us the night of the 4th. We will see an Atmospheric River event set up and be coming right in on us. The moisture source here is a deep one so this is why the expectation is for above average rain and snow. And yes, we will see heavy snow for the mountains as it appears right now. Snow levels could be as low as 2500 feet near Mt. Shasta and 3500 feet elsewhere on this first arriving system. After that, snow levels look to be landing mostly in the 4000 - 6000 foot range. We will see snow continuing in the mountains for just about all of the first half of the month with no prolonged breaks expected. This is great news for the winter recreation areas like the ski areas. It also is great news for building the snowpack we need to help keep us moist and less likely for a severe fire season this year.