Wednesday, 12/21: Winter has officially arrived, and our weather will reflect it. Unsettled conditions are expected at times for the upcoming 7 days, with a weak system affecting our weather from now through Thursday. A strong system is expected for late Friday and Saturday. This system has the possibility of producing significant mountain snows, widespread rain, strong winds, and even a possibility of high desert snow. Could be a White Christmas for the mountains and some high desert communities!
WEDNESDAY NIGHT - THURSDAY
*Update 9:00p Wednesday* - the storm off the coast has intensified this evening, and a band of precipitation blossomed to our south, providing lift for a good soaking this evening. Moderate to heavy rains are covering nearly all of Southern California, including all deserts and mountain areas. southeast flow ahead of the storm is allowing the deserts to see more rainfall than many coastal areas. My original notes earlier called for some areas to see up to 0.50 inch, and others with just sprinkles... but it appears now that almost all locations will see at least 0.10 - 0.30 inch, with the possibility of higher amounts over 0.5 inch if the storm continues to churn off the coast tonight and tomorrow. This could be the "surprise soaker" of the season. Be careful on area roads as they are experiencing some flooding. Some washes may begin to flow as well.
(Original discussion): For today, a weak system to the west of Baja California is bringing up loads of moisture and some diffluence, allowing for mostly cloudy skies and scattered showers. This is expected to continue tonight and into Thursday, before skies begin clearing sometime Thursday afternoon or evening. A thunderstorm or two is also possible tonight or Thursday. Amounts are expected to be highly variable, with some areas only reporting sprinkles, and others possibly seeing heavier showers and possibly over 0.25-0.50 inch. Southeast winds aloft will allow for the possibility that clouds will bank up along the east slopes for a time, with rainfall chances perhaps a bit higher along the foothills and a bit lower further from the nearby mountains. This storm is of warm origins, so snow is only expected far up on the highest nearby peaks, likely over 9,000 feet. Wednesday night low: near 50. Thursday high: 60-65.
THURSDAY NIGHT - FRIDAY
Skies will be clear to partly cloudy, with cool temps and light winds Thursday night. By Friday, the strengthening storm will begin diving southeast toward California. Clouds will begin to increase later Friday, as well as the possibility of increasing southwest winds once again late in the afternoon. Lows Thursday night: mid 40's. Highs Friday: mid 60's.
FRIDAY NIGHT - SATURDAY NIGHT
A strong storm is expected to move across California during this time frame.
Ahead of the cold front, strong southwest winds are expected to blow, with gusts potentially surpassing 60mph. It is possible the southern areas and foothills will once again experience some of the strongest gusts, with blowing sand and debris a possibility. As the storm moves closer, the chance of rain will increase Friday night and into Saturday evening. The cold front is expected to pass through sometime Saturday morning or early afternoon, with the highest possibility of desert rain during that time frame. Winds may shift to the west or northwest behind the cold front, and may become better focused along the I-10 corridor and the highway 62 corridor up into the 29 Palms area.
As the cold front passes, temperatures will drop, and the snow levels are expected to fall to near 3,000 feet by Saturday night. This could have SIGNIFICANT travel implications. Some highways that could be affected by snow at the 3,000 level include:
- I-15 Cajon Pass, and over Mountain Pass, south of Las Vegas.
- Highway 62 summit near Yucca Valley
- Highway 74 in the mountains south of Palm Desert
- Highway 243 in the mountains south of Banning, into the Idyllwild area
- Highways 18, 330 and 38 into the San Bernardino Mountains
- I-5 over the Grapevine, north of LA
If the snow level were to lower more than expected, it is possible I-10 in the Beaumont and Yucaipa areas could get a few flakes, as well as Joshua Tree and Morongo Valley.
Rainfall and snowfall amounts are still tough to predict, as the storm is coming together. However, it is likely the urban areas to our west will receive 1-2 inches of rain, the lower mountain slopes may receive 2-4 inches of rain, with 6-16 inches of snow expected in the higher elevations. The deserts could see anywhere from a trace to 0.50 inches of rain.
Saturday high temps for PS are expected in the 58-65 range. Low temps Saturday night should be in the upper 30's - mid 40's.
SUNDAY - MONDAY
Looks like Christmas and Monday will be clear and cold, with high temps in the upper 50's to low 60's. Low temps could fall into the 30's Sunday night.
Some computer models show another weak southern system, like the one we are experiencing today, to swing by on Tuesday. Other models show no effects on our weather. Therefore, confidence is low in next week's forecast. Best trends suggest a small chance of precipitation near Tuesday, with fair weather Wednesday and Thursday next week.
This next set of storms will dump another 1-4 feet of snow in the Sierras, for another much needed boost in the mountain snow pack. Dare I say it - but this is beginning to look like a good winter for the state, especially in the Central and Northern areas. Really hopeful this pattern will continue!
Happy Holidays to everyone - stay safe and watch media reports for updated travel advisories on Saturday!