The West Coast is prepping for the first atmospheric river (AR) of the season. The river of moisture in the sky sets to slam Oregon, Washington and Northern California beginning on Monday.
The FOX Weather Center is watching carefully to see if this storm will be the first of many, similar to the battening the West took last winter from the parade of atmospheric river-fueled storms. Researchers caution that the devastating 2022/23 winter was during La Niña. This 2023/24 winter is in El Niño, making the atmospheric river connection more likely.
“During El Niño, when the eastern Pacific Ocean is warmer than normal, atmospheric rivers are more likely to impact the western U.S.,” wrote NOAA’s Climate Prediction Office in a study. “Conversely, during La Niña, when the eastern Pacific is cooler than normal, atmospheric rivers are less likely to impact the western U.S.”
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An atmospheric river can carry up to 27 Mississippi Rivers’ worth of water. A warm front sweeping over the Pacific Northwest Sunday will direct the AR hose to the Washington and Oregon coasts Monday. The areas can expect a strong atmospheric river event, Category 4, according to the Center for Western Weather and Water Extremes (CW3E). Northern California is forecast to see a moderate event.
“The first and strongest is the moderate to low-end strong atmospheric river that is still slated to impact the (Pacific Northwest) Sunday night through Monday,” stated the NWS Portland Office in a discussion. “Models show the jet streak peaking around 30–50 knots (35-58 mph) pushing through the region during this time period along with a significant amount of upper-level moisture.”
This translates to a rainmaker, especially in higher elevations. Commuting on Monday will be tough.
“And we’ve got significant rain to come, I mean, easily 3 to 5 inches, up to eight inches in higher elevations. And you might be thinking, okay, well, this last system that we saw that moved out of the Rockies brought in a little bit of snow up through the Tetons,” said Meteorologist Jane Minar.
“Well, not this one, unfortunately. We’re not going to say the S-word this go around. It’s really just a bit too warm,” she continued. “We do expect that it’s going to be all rain even up into the higher elevations of the Cascades. It is more of a rain event that it is a snow event.”
“Most of this rain will be beneficial as areas begin to recover from severe to extreme drought conditions,” stated NOAA’s Weather Prediction Center. “Heavy rain could lead to impacts associated with debris flows from this season’s burn scars across northwest California and southwest Oregon, where Flood Watches have been issued.”
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The AR connection will be in place through the early part of the week. The strongest storm will dump the heaviest rain on Monday. The next in a series of storms comes through Tuesday and Wednesday. The forecast stays showery through the work week.
The NWS forecasts a strong El Nino to last through the winter.