Continued rain & winds, possibility of thunderstorms
Excerpt from today’s AFD:
.UPDATE...
Issued at 815 AM PST Mon Feb 19 2024
Another gorgeous morning for most as much of the large scale
forcing has moved out of the area with main front now situated
along the Central Valley and down through the Central Coast. Moist
upslope flow continues throughout the day as the low remains
spinning offshore, so locations like the Santa Cruz Mtns will
continue to see periods of light rain throughout the day. With the
clearing this morning, this will aid in further destabilizing the
atmosphere as the surface warms and the air aloft continues to
cool. Forecast surface based CAPE on the order of ~500 J/Kg and
effective bulk shear 30-40 kts for areas mainly north of the
Monterey Bay will be more than enough for a few thunderstorms to
initiate and sustain themselves as they move inland off the
waters. As of writing, isolated cells moving through the waters
off the North Bay coast have been showing consistent signs of
rotation. Would not be surprised to see a waterspout or two today
along the coast with a marginal chance for a very brief tornado
threat to land, particularly from Monterey Bay northward and
inland areas from about Livermore through Napa County. This low
threat of a brief tornado decreases as we lose surface heating
heading into the evening and the vertical wind field becomes more
uniform. A brief wind threat is also possible from these storms
as well. Given steep low level lapse rates allowing for efficient
vertical mixing, a brief gust or two of up to 60 mph appears
plausible from any of the stronger cells.
Behringer
&&
.SHORT TERM...
(Today and Tonight)
Issued at 1200 AM PST Mon Feb 19 2024
SW-NE oriented rain bands have been persistent across the North
Bay and the Santa Cruz Mtns/Santa Clara Valley/East Bay regions
as the surface triple point (intersection of occluded, warm, and
cold fronts) continues to approach the Bay Area. Flood Advisories
continue for much of the area with minor impacts ongoing. More
rises on creeks/streams are being observed as well as increased
reports of roadway flooding early this morning.
Looking ahead...High resolution guidance has been consistently
hinting at the potential for a heavy/convective rain band setting
up across the Bay Area later this morning. There is still
uncertainty on if/where this narrow feature will set up and if it
will stall. Upper level support will be favorable for large scale
ascent through the afternoon, drawing in all that subtropical
moisture (PWATs of around 1"). If convective bands were to train
and stall for many hours today, this could result in more serious
flooding impacts. We`ll be watching this closely through the
morning. Chance for thunderstorms still look decent through early
this vening, especially for the North Bay and the interior East
Bay bordering the Sac Valley. A few stronger storms are likely,
with gusty winds, hail, and perhaps a brief tornado. Continue to
be weather aware today and have many ways to receive weather
alerts.