Note: After today, forecasts will not be issued for an unknown duration (My mother not expected to survive the week).
Having to take days off at a time makes it difficult forecasting the weather (no continuity). It certainly got warmer than I expected this past weekend. Despite a not so strong, high pressure aloft, low level, off-shore flow was efficient enough to promote widespread 80 degree weather for a couple days (as many computer models predicted...a bit higher than actual forecasts, though).
The off-shore flow is transitioning to weak on-shore flow today (areas of low clouds/fog visible on satellite imagery around the coastal islands). A return to seasonable temperatures for most areas should occur tomorrow (thanks to a shallow marine layer). An approaching storm is expected to bring wet weather to much of southern California on Wednesday (some chance beginning late tomorrow evening western half of the region). Although it's weakly tapped into an atmospheric river, the storm is forecast to weaken considerably as it nears the state coast (upper level portion outrunning it's low, level circulation...never good for the health of a storm). The bulk of precipitation should fall Wednesday morning followed by scattered, instability showers (ending early Thursday most areas).
Storm totals in Santa Barbara County could exceed half an inch (one inch in favored, mountain locales), but totals should be considerably lower farther to the east. In the L.A. Basin, I'll be surprised if rainfall reaches a quarter inch (away from foothills/mountains). It may only amount to a few hundredths of an inch rain, if some model solutions are right. There is a small chance for a few, brief-lived, thunderstorms, but that should be mostly west of L.A. County (excepting around the mountains in the afternoon). Snow levels should fall to 6000 feet or slightly lower later Wednesday into Thursday, but the predicted, rapid weakening of the storm should limit snowfall to a couple inches at most.
The numerical models keep residual, low level moisture in place after the storm exits the Southland. So, marine layer clouds may be widespread Friday morning, but they should dissipate quickly in most areas to yield mostly sunny skies that day. A new storm is forecast to affect northern California Saturday morning, but it should stay too far north to threaten showers down in the Southland. Weak, off-shore flow may promote warmer than normal weather early next week, but many model solutions show widespread, wet weather around the middle of next week. Some model scenarios show a good soaker. However, the same was predicted by some models for the approaching storm this week (no longer likely).
UCLA Forecasts and analyses are written by James Murakami
– posted: 2019-03-18