September 29, 2018
Summary: Temperatures this afternoon are ranging 14 to 18 degrees cooler than yesterday at this time. As of 1:00pm, all locations were reporting readings in the mid 70s. The big push of marine air into the valley has subsided for now. Winds at both Pacheco Pass and Travis Air Force Base are at less than 10 MPH.
The first low pressure system is entering northern California. It’s only marked by some high, thin clouds over central California. Now that the valley is pooled with marine air, temperatures will remain well below average Sunday, but will begin to warm a bit Monday due to a developing southerly flow ahead of our next low pressure system which models continue to indicate will give our region the first rainfall since April 16. This will be an interesting system as models continue to suggest a good moisture field will wrap around the low for a good chance of measurable rain throughout the valley beginning later Monday night and lasting possibly through the day Wednesday.
In the meantime, mighty Rosa is now a cat 2 hurricane with maximum sustained winds at 105 MPH. The National Hurricane Center is projecting Rosa will weaken beginning tonight and its current northerly track will switch to a northeastern path, trekking across the northern Baja peninsula Monday. Models this afternoon show very little change in the projected path, or how far north moisture from Rosa may progress. It is likely the real rich tropical moisture will cross the Imperial Valley and go up through Las Vegas. It’s possible high level moisture could work as far north as southern Kern County, but this moisture will be mainly high level and shouldn’t have much of an impact.
Precipitation amounts may range from .10 to possibly .33 of an inch. If isolated thunderstorms develop, then locally .50 amounts would be possible but that seems unlikely at this time. A new trough will swing through central California Thursday. At this point, it looks like the valley will remain dry with perhaps a chance of showers over the Sierra Nevada. This feature will do a good job in keeping temperatures below average with possibly some low to mid 80s next weekend. Beyond that, a trough of low pressure is projected to remain over the west well into next week. No rain is expected, but pleasant fall conditions will continue.
Forecast: Mostly clear tonight through Sunday with occasional high clouds. Mostly clear Sunday night, becoming partly cloudy Monday, morning. Increasing clouds by Monday afternoon. Mostly cloudy Monday night through Wednesday with a chance of showers Monday night and the likelihood of showers Tuesday through Wednesday with a chance of thunderstorms. A chance of showers Wednesday night. Becoming partly cloudy Thursday. Mostly clear Thursday night through Saturday.
Short Term: Overnight lows will fall into the upper 40s to the mid 50s north of Kern County and the mid to upper 50s in Kern County. Highs Sunday will warm into the lower 80s. Lows Sunday night will chill into the low to mid 50s, perhaps the upper 50s to lower 60s in Kern County. Highs Monday will range in the mid 80s.