Storm brings snow to multi-state area; strong winds due in southern California. Warmth to return.
After a prolonged period of springlike weather a cold upper-air disturbance is bringing a return to winter weather conditions across portions of the west.
Winter weather advisories, a winter storm warning as well as flood warnings and advisories have been issued across portions of Montana, Idaho, Wyoming and the Dakotas as well as for northern Utah and northern Colorado.
High pressure has temporarily released its hold, allowing an “inside slider” to drop south, forming a cut-off low over southern Nevada by early Wednesday morning. The circulation around this pocket of cold air has brought a temporary end to unseasonably mild conditions which have prevailed for the past week all across the western U.S.
Mostly affected by this pattern are areas mentioned above, with snowfall and strong winds circulating around a deep 985 millibar low over the Kansas-Nebraska border this Tuesday, March 11. As this low moves southeast, cold arctic high pressure will follow, but gradually moderate, with a return to seasonal temperatures later in the week.
This pattern is expected to generate strong northeast Santa Ana – type winds beginning Tuesday in southern California for about a 24 hour period. A wind advisory will begin this evening across southern California, most notably across mountain areas, and areas below inland empire canyons and passes. Gusts in these areas could reach upwards of 60 mph later tonight. This could require upgrade to high wind warning status, and would likely affect travel on certain travel routes. Additionally, a fire weather warning is now in effect for Los Angeles and Ventura county mountain areas due to very low humidities, and unseasonably warm temperatures.
Surface pressure gradients are expected to intensify significantly through Wednesday morning, and while this event isn't expected to be widespread, some of usual windy locations may be subject to briefly hazardous windy conditions.
These conditions aren't expected to be long-lasting; by Wednesday afternoon both surface and upper air pressure gradients are expected to weaken significantly, resulting in a noticeable decrease in surface winds.
Once again, prevailing high pressure settling in will bring a return to warmer than average conditions all across the west later in the week.