Winters across the Pacific Northwest can be a bit of a soggy mess for lower elevations and a winter wonderland across the higher elevations thanks largely in part to atmospheric rivers, which are very common in winter months.
This week is no exception as a powerful atmospheric river is taking aim at the Pacific Northwest, and the event kicks off on Monday.
(For More:What is An Atmospheric River?)
Level 4 of 5
This upcoming atmospheric river has been rated a level 4 of 5, according to the Center for Western Weather and Water Extremes (CW3E).
So what does that mean?
It means that this atmospheric river will likely bring days of heavy lower elevation and coastal rain as well as mountain snowfall to the higher elevations of the region.
Various National Weather Services have warned that this atmospheric river event has the potential to impact their areas, and flood watches are already in effect for Seattle and Portland for most of the week.
The Weather Prediction Center has identified multiple days with a level 2 (of 4) risk of excessive rainfall, and many of the same areas are in the bullseye multiple days in a row.
With this atmospheric river, and much of the West for that matter, being warmer than usual for this time of year, snowfall is only expected at the highest peaks this week.
Timing of the Event
The first round of rain is kicking off on Monday, when the atmospheric faucet really turns on and rainfall rates to an inch per hour are possible. This could lead to totals potentially reaching 5 inches across the coast and the Cascades.
Winds will also be strongest with this first round.
Widespread gusts to 30 mph with isolated gusts over 40 mph could bring down tree limbs and take out power lines.
The next round of moisture will surge onshore Tuesday into Wednesday. While this surge isn't currently forecast to be as strong, soils will start to become saturated after Monday's moisture, so flooding will begin to become a concern as the week progresses.
End Of Week
By Thursday, the heaviest rainfall will begin to decrease, which is good news.
However, as water begins to run off and collect in streams and rivers, there is a chance of river flooding by the end of the week and into the weekend.
In total, widespread rainfall amounts of 3 to 6 inches are possible by the end of the week, with higher elevations in the Cascades potentially seeing 6 to 12 inches.
Beneficial Yet Excessive
You ever hear the phrase, "too much of a good thing can be a bad thing"?
That may not even be the right quote directly, but I hear it all the time.
This quote applies to atmospheric rivers as well.
The Pacific Northwest is in drought. The map above shows all the areas that are in at least some drought.
But, too much rain too fast doesn't really help as much as you would expect.
The drought-stricken soil cannot absorb heavy rainfall fast enough, and as a result, runoff commences.
Rivers get saturated, and the drought doesn't decrease as much as you would expect.
