Colder system will bring widespread CA rain this weekend, with modest flood risk SoCal

Respectable late-season storm will bring widespread CA rain this weekend; local SoCal flood risk possible

Today’s blog update will be a relatively quick one, but I wanted to get at least a quick post up since it does appear that the present active and cool pattern will start to wind down after this weekend’s more substantial storm–perhaps representing winter’s last gasp in some areas.

The feature of interest will be a modestly fast-moving low pressure system that will swing southeastward along the CA coast between Friday and Sunday. It will first bring widespread soaking rain, locally gusty winds, and higher mountain snowfall in NorCal (including some decent accumulations over the Sierra passes). It’ll then move across SoCal later in the weekend–dragging a band of moderate to locally heavy rain across the region. The Transverse Ranges will (once again!) be favored for some heavier precipitation in this pattern, though we won’t see totals anywhere near as high as multiple severe rainstorms earlier this season. Given how saturated soils already are, though, with ongoing landslides and slope failures even amid sunny conditions in recent days, it’s plausible that yet another widespread soaking could lead to localized flood and/or earth movement issues (mudslides/landslides). To be clear: I do not think this will be a major flood event in SoCal, but there could be some localized issues and urban flooding that could cause some disruption at times.

As has now been the case for essentially every storm this season, the coming system will likely be associated with enough atmospheric instability for at least some isolated thunderstorms (mainly Sat in NorCal and Sun in SoCal). This does not appear to be a particularly noteworthy thunderstorm setup compared to others this season, but there will still be the outside change of an isolated stronger cell or two that drops larger hail, a funnel cloud, or produces localized flooding problems somewhere.

This weekend’s storm won’t be extreme by any means–but it will be respectable by late March standards, especially across portions of SoCal that may see a pretty wet weekend overall. It’ll also top up the (already decent) Sierra snowpack, likely contributing to April 1 snow survey results pretty close to the long-term average (something of a feat in recent years more often characterized by either very low or very high snowpack!).

Drier and warmer conditions possible early-mid April

There may be one additional (though weaker) system that could bring some additional showers, isolated thunderstorms, and Sierra snowfall later next week. But after that, there are some signs of a quieter and warmer pattern developing that could persist until at least mid-April. Right now, seasonal models are suggesting relatively high odds that California will warm up rather fast starting in May and June this year–so I don’t necessarily expect last year’s long, cool, and wet spring to be repeated this year. For more discussion on this latter point, join me for my next live weather and climate office hour on YouTube (see below for details!).

My next live weather and climate “virtual office hour:” Mon, Apr 1, 4pm PT

Topic: I’ll discuss what this year’s California’s precipitation, temperature, and snowpack imply for water resources and wildfire risk in the coming months. Plus, an update on La Niña and what its impending rapid development might mean for California and beyond.