One of the stronger systems to impact Southern California this winter will drop right into the LA Basin/San Diego area tonight bringing pre-frontal strong, gusty winds, then a spell of heavy rain before the upper low drops directly overhead of SOCAL. Once the front pushes through, expect heavy, thundery showers, gusty, cold backside winds, particularly along the coast. Watch out as snow levels drop off sharply once the front passes through. Travelling I-5 or through the Grapevine or I-15 over Cajon Pass tonight or through the passes linking San Diego and the desert? Be sure to check out and watch for quickly changing weather conditions. It was AccuWeather’s Bernie Rayno who rightly pointed out that wet roads fron earlier rains may ice up fast along with precip quickly changing from rain to snow. Several inches of snow is possible even down to pass level and with strong winds, visibility would likely be greatly reduced. Closures are possible, especially over the Grapevine of I-5. The higher reaches of the San Gabriel and San Bernardino Mountains may pick up 1-2 FEET of snow as this storm system barrels right over the area tonight.

While it’s blustery, heavy and thundery showers with the possibility of hail, snow levels are down to 2,000, maybe 1,500 feet tonight and that means snow down to the valleys and basins of the Mojave Desert so please be careful if travelling between LA and Vegas.

Here’s the NCEP GFS vort heights for Wednesday morning which shows the deep upper low which pulling down the cold air aloft and will support the sharp cooling at 850, reducing snow levels from 5-6,000 down to 2,000ft overnight. Note the very strong upper winds hooking around the base of that upper low.

During Wednesday, this system marches east dragging colder air through the Southwest, heavy rain showers will impact Phoenix and Tucson while Flagstaff and other mountain resorts are likely to get walloped by heavy snow, perhaps accumulating to over a foot, maybe even nearer 2 feet before this thing heads for the Plains.

You can see from the height vort max chart at 42 hours, so a little later in into tomorrow, the core of the upper low pushes east but SOUTH of Las Vegas, this may allow wet snow flakes to fly on the strip!

See my next post for details on the Plains blizzard.

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