Rain on the way, forecast for Dec 18th

A very interesting day as the lower level of our atmosphere sees the lingering effects of our recent dry and warm offshore wind event. At the upper levels, clouds are increasing and showers are expected to arrive soon. We should see only a very slight chance for isolated sprinkles in our northern areas tonight as the dry lower levels of the atmosphere struggle to get saturated enough to allow for rain. Overnight lows will be mostly in the 50's and 40's as winds pull up mild air from the southwest. Sprinkles and light rain will become likely for early Monday morning along the Central Coast. Scattered sprinkles and light rain will spread in to the Santa Barbara Channel through Monday and in to Tuesday. The first round of showers will bring rain totals on the order of one quarter to about one inch of rain. Winds will be gusty from the south and snow levels will stay pretty much above the highest elevations of our local mountains.

Looking ahead, the core of the storm system will approach Central and Southern California by the mid and second half of the work week. This is where things get interesting as many weather variables are all pointing toward very solid potential rain totals. First, southerly winds will drive moisture upslope which is referred to as orographic lift. Rain basically gets squeezed out of the clouds along south facing slopes. We also see some cold air rushing in from the north which will collide with the warm tropical air from the south. This could lead to heavy rain and even thunderstorms which usually produces heavy down pours. The last variable is an ample supply of moisture, which as mentioned, is streaming up from the south. With all of this expected, rain totals through about Thursday could exceed 1 to 3 inches for the coastal plains and much more for foothills and mountains. Details will of course need to be watched as per exact timing and expected intensities. We will be vigilant as always and update all of our media platforms as needed all next week. Beyond Thursday and in to Christmas weekend, we expected drier weather and gradual warming to return to the region.