October 1, 2018
Summary: Temperatures this afternoon are running anywhere from 4 to 8 degrees higher than 24 hours ago due to a weak southerly flow at the surface and milder air being pulled around the southwestern flank of the off shore low. It’s quite interesting this afternoon to observe what is occurring to our south. It appears former hurricane Rosa which has winds of 45 MPH at this time has slowed down a bit and will cross the north/central Baja peninsula tonight and will be in the Gulf of California Tuesday, becoming a remnant low. The real rich tropical moisture is now crossing the California/Mexico border and into extreme southern California. High clouds from Rosa have pushed as far north as northern San Bernardino County and will be reaching into Kern County tonight. Dew points have gone crazy south of the Tehachapi Mountains. High desert locales are reporting dew points as much as 20 to 30 degrees higher than yesterday at this time. Some cloud build ups were also evident over the Kern County mountains as of 1:00pm.
Over the eastern Pacific, we have a rather impressive for the time of year low pressure system which is behind modeling schedules. A cold front extends out from the low through northwest California then southwestward to off the central coast. Light showers had spread as far south as the San Francisco Bay area earlier today but have temporarily migrated back northward. The cold front from this system will begin to push inland Tuesday night and Wednesday. We may see some light showers ahead of the front late Tuesday, especially later in the day, but the best chance of picking up measurable precipitation will be from late Tuesday night through Thursday morning. I’m still not completely convinced some of Rosa’s moisture won’t become involved with this system. If it does happen, it would certainly enhance precipitation amounts. Most models, though, keep that moisture south of the Kern County mountains.
Rainfall amounts from late Tuesday through Thursday morning could tally up to a tenth to a quarter of an inch with locally more, especially in the south valley. Precipitation should be over by Thursday afternoon with dry weather returning for Thursday night through Friday night. Over the weekend, a broad trough of low pressure will cover the western states. Some models are showing a fast moving wave of low pressure trying to move through southern California late Saturday for a chance of showers over the mountains. For now, it looks like the valley will be dry. That trough will remain in some way, shape, or form through next week, keeping temperatures near to somewhat below average.
Forecast: Partly cloudy tonight. Mostly cloudy Tuesday through Thursday morning with a chance of light showers Tuesday. Showers becoming likely late Tuesday night through Thursday morning with a slight chance of thunderstorms. Partly cloudy Thursday afternoon. Mostly clear to occasionally partly cloudy Thursday night through Monday.
Short Term: Lows tonight will range from the upper 50s to the mid 60s. Highs Tuesday will be in the low to mid 80s. Lows Tuesday night will be in the mid 60s. Highs Wednesday will be in the upper 70s.
Wind: Winds will be generally less than 12 MPH tonight then will be out of the northwest at 10 to 15 MPH Tuesday through Wednesday with local gusts to 25 MPH, especially near showers.
Next report: Tuesday, October 2