LONG RANGE FORECAST THROUGH THE MIDDLE OF APRIL - 4/7/2019
April is the first full month of spring. April typically is when we see the heavy rains and snows of the wet season wind down. Early April in Southern Oregon can be still be very chilly to even cold. The Pear Blossom Festival during the second weekend of April in Medford is usually plagued with colder temps and showers if not rain. Snow can still fall to low elevations. Typically April will have highs in the 60s and 70s at the beginning of the month which becomes mostly 70s with some 80s by the end of the month for highs. Overnight lows can be quite chilly through mid month. Most locations in the region will still have the risk of frosts. April on average is typically going to give us about one and a third inches of rain in Medford. Elsewhere west of the Cascades we can see as much as 2 inches of rain. April will generate about 2 -3 inches of rain along the Coast in a normal year. East of the Cascades there will typically be about a half inch of rain. Snow levels in the mountains usually are going up, but snowfalls up to 3 feet above 4500 feet have occurred in April. So what can we expect for early to mid April?
EVERY single long range forecasting source I have seen said April will be warmer than average and drier than average. Some of those forecasting outlets predicted April will be much below average for precipitation. We KNOW now this is not going to be true at all. And we also know now that both sides of this are going to be wrong through mid April. We can see int he longer range data coming out that temps will be cooler than average. In large part this is going to be due to persistent cloud cover and airflow coming more from the west northwest. Yes, at the current time we have a very tropical southwesterly flow coming up over us. That is going to change. When we do get back to west to northwest flow, we will see temps running a good 10 degrees below average. This means areas west of the Cacades are going to be seeing mid 50s to mid 60s where we should be running up in to the 70s. The same thing will be happening in the mountains and east of the Cascades.
As for rainfall, we are going to see as much rain as we would normally see for the entire month, by the middle of the month. In fact, most locations in Southern Oregon and Northern California will be at and then well above their average April rainfall by the time we hit the 9th. And, we could easily be 2 to 3 times the average amount. All of this is due to the Atmospheric River flowing in over us bringing us very unseasonably heavy rains to the area. Being that this airmass is so warm, snow levels are very high right now above 8000 feet at least. We are going to see snow packs melting under the combination of the rain and warm air. This will help enhance the potential for flooding through at least the 9th, and possibly longer. We do have good news in that colder air is going to return. This will cut snow melt way down. And, we will see snow levels really dropping. It looks as though they will be down near 4000 feet by the 12th. It is expected we will be seeing more rain and snow coming in through mid month for sure. In fact, it looks like we stay wet and cool through the end of April now according to all the latest data.