Possible heavy winds, t-storms, and small hail today and tonight

NWS OPC forecast for 00Z Sun Mar 24 (5pm PDT Sat Mar 23). Front has passed. A series of minor surface troughs will be passing through, which could bring some isolated locally heavy winds, t-storms, and small hail.

12Z Mar 23 (5am PDT Mar 23) surface analysis shows surface trough that has already passed through. This was the minor trough of concern. Others may follow, such as the approaching one shown in the 00Z Mar 24 forecast above.

18Z Mar 23 (11am PDT Mar 23) sfc analysis:

Storm arriving this afternoon

NWS OPC Forecast valid 00Z Sat 3/23 (5pm PDT Fri 3/22). Cold front is passing through Bay Area, immediately followed by low pressure system and associated trough that will bring convective lifting and the possibility of thunder storms. This is not expected to be a big rainmaker overall, but there is a possibility of locally heavy rain, moderate to high winds, small hail, and some thunder and lightning.

Another storm Saturday night, lingering showers Saturday/Sunday

From latest AFD:

.SYNOPSIS...
Issued at 159 AM PST Sat Mar 2 2024

A cold front is moving through the Bay Area early this morning.
Showers and strong westerly wind will continue Saturday before
tapering off Sunday. Cold temperatures will persist through
Monday.

&&

.SHORT TERM...
(Today and tonight)
Issued at 159 AM PST Sat Mar 2 2024

The surface cold front is currently moving through the Bay Area.
Doppler radar velocity data and higher elevation anemometers are
indicating winds are gusting as high as 55 mph as the frontal
boundary passes. Rain showers continue, although the coverage has
decreased overnight. The post-frontal environment will likely
continue to support this lull in precipitation Saturday morning,
and there will even be some sunshine. By Saturday afternoon, the
combination of surface heating and cold middle levels will
decrease the stability and will likely lead to a final round of
strong showers and possible low-topped thunderstorms. Winds will
subtly shift from SW to westerly behind the front, and remain
strong through the day.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 159 AM PST Sat Mar 2 2024

High pressure will quickly build behind the front and the gradient
will relax by Sunday. There may still be a few showers, but they
will be lighter than Thu-Sat. Winds will also be lighter on
Sunday, but there will still be a moderate westerly breeze in the
afternoon. The biggest impact will shift from wind and rain to
cold morning temperatures. The low temps on Sunday and Monday
morning are expected to range from mid-30s to low-40s.

A weak system will move through in the middle of the week. This
will keep the cooler temperatures, cloud cover, and light rain
chances in the forecast through Tuesday or Wednesday. High
pressure finally rebuilds late week. Thursday and Friday look to
be clear and calm, with more normal temperatures. For example, the
Thursday high temperature at Santa Rosa is expected to climb back
to the mid-60s for the first time in a week.

Special Weather Statement

San Fransisco Peninsula Coast CA-Santa Cruz Mountains CA-
Santa Clara Valley Including San Jose CA-
San Francisco Bay Shoreline CA-
529 PM PST Fri Mar 1 2024
...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN SANTA CRUZ...
SOUTHEASTERN SAN MATEO AND NORTHWESTERN SANTA CLARA COUNTIES THROUGH
600 PM PST...
At 528 PM PST, Doppler radar was tracking a strong thunderstorm 10
miles west of Boulder Creek, or 18 miles southwest of Saratoga,
moving northeast at 35 mph.
HAZARD...Wind gusts up to 40 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
San Jose, Sunnyvale, Santa Clara, Redwood City, Mountain View, Palo
Alto, Cupertino, Campbell, Menlo Park, Saratoga, Los Gatos, Los
Altos, East Palo Alto, Los Altos Hills, Atherton, Woodside,
Fruitdale, Boulder Creek, North Fair Oaks, and Stanford.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.

Wet and windy Friday through Sunday

From AFD:

.SYNOPSIS...
Issued at 112 AM PST Fri Mar 1 2024

Expect a nasty couple of days ahead as a second cold front moves
through the Bay Area. Strong winds will pick up this afternoon.
Periods of rain will persist through Saturday with cold weather
sticking around into next week.

&&

.SHORT TERM...
(Today and tonight)
Issued at 112 AM PST Fri Mar 1 2024

The rain forecast is holding steady and gauges overnight are more
or less agreeing with the expected accumulation so far. There are
some exceptions where stronger rain bands were able to persist for
several hours. These include over 1.5" at Ben Lomond and similar
totals throughout the higher peaks in the Santa Cruz Mountains.
The Santa Lucias have also over performed, with several gauges
already over 2". Otherwise, the forecast has been very good so
far. With roughly another 1-2" expected over the next 48 hours,
there are still no major flooding concerns expected this weekend.
That being said, the rain combined with a cold wind will not make
for great picnic weather.

Strong SW winds will increase through the day ahead of the
frontal passage tonight. Gusts to gale force are expected,
especially as the frontal boundary moves through in the afternoon
and early evening. After the front passes, winds will shift to
westerly, but remain strong through the night. A wind advisory is
in effect for the majority of the area from noon today through 10
AM Sunday.

&&

.LONG TERM...
(Saturday through Thursday)
Issued at 112 AM PST Fri Mar 1 2024

Saturday will feel like the Pacific Northwest. In addition to
periods of rain, it`s going to start cold and won`t warm up very
much. The official forecast for San Francisco has a low of 46F
with the high only reaching 53F. While that`s nowhere near the
daily record (lowest max temp) of 45F set in 1896, it`s 9 degrees
below normal and more in line with the average March high temp in
Seattle (54F). The majority of the rainfall looks to be in the
morning, with only scattered showers in the afternoon. Winds will
also be lighter than Friday, but there will still be a stiff
westerly breeze through the day, especially along the Central
Coast. The first real snow of the year is expected in the
mountains as the thickness finally drops low enough during the
tail end of the multiday rain event. There`s some instability,
but the air mass will be drying out in the post-front environment.
The 06Z NAM point sounding for Santa Rosa valid at 10AM Saturday
brings the freezing level to 1465` with 142 J/kg of CAPE. The
problem is the precipitable water is only 0.38" at that time, and
continuing to decrease through the day. A few inches are expected
in the higher peaks of the Mayacamas and Santa Lucias, around an
inch in the Diablo Range, and a possible dusting in the Santa Cruz
Mountains. To be clear, the snow levels will remain above 2,000
ft and will not impact the main mountain passes.

The rain will really taper off Sunday, but the cold temperatures
will linger through the week. Monday morning looks to bring the
coldest temperatures with most areas dropping into the mid to
upper 30s before the sun comes up. The remainder of the week will
have lows in the upper 30s to mid 40s and highs in the upper 50s.
Some light rain is possible mid week. The uncertainty is much
higher than normal beyond Thursday with the global models all over
the place by next weekend.
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