Major springtime convective event across California

This will be a relatively short update this evening, but the incoming storm system is quite impressive. Major cloud top cooling and enhancement is noted on satellite imagery in a region of strong divergence  aloft ahead of the incoming low pressure area. Heavy rain is developing along a strong cold front just west of the far Northern California coast which will move ashore and southward through the overnight and morning hours.

IR satellite imagery depicting the incoming low pressure system (NRL)

By late morning, however, partial clearing behind the front will usher in a very unstable airmass. I think model progs may be significantly underestimating surface heating and thus surface-based CAPE (even though they are spitting out pretty high values right now). While the expected setup is not ideal for severe weather in NorCal, isolated large hail or damaging winds are certainly possible tomorrow. If one of the stronger vorticity maxima can rotate inland during peak heating, it’s possible that a line of organized strong thunderstorms could develop in the Central Valley and bring widespread lightning, torrential rainfall, and lots of hail.


Low freezing levels and the potential for strong updrafts portends a high likelihood of hail in virtually all stronger convective elements tomorrow. All in all, I expect tomorrow to see widespread convection and at least scattered thunderstorm coverage, if not more numerous storms. This system is expected to bring pretty substantial rainfall for April–upwards of one inch in the hills and in places that get hit with convective showers. SoCal will not miss out on all the action; it just might take until Wednesday for the most unstable air to reach Los Angeles and San Diego. This low now appears to be slow moving out of the region, and the models linger shower and possibly even thunderstorm chances into at least Thursday and possibly Friday across much of the state. All in all, a very active 72-96 hour period shaping up for CA.

Finally, the models are very consistent in bringing a similar system into the region in 7/8 days. This is turning out to be a very memorable spring, after all…


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