Hail in California, February 26, 2018

Area Forecast Discussion
National Weather Service San Francisco Bay Area
153 PM PST Mon Feb 26 2018

.SYNOPSIS...Look for scattered showers to continue into the
evening, along with a slight chance of thunderstorms. Snow levels
will drop as low as 2000 feet today and light snow accumulation is
likely on the highest peaks today. Locally breezy conditions will
develop near the coast this afternoon and in the hills tonight
and Tuesday morning. On Wednesday night and Thursday a stronger
and wetter storm system will likely bring widespread soaking rains
to our region, with showers to follow from Thursday night through
at least Friday night, and possibly into Saturday. Temperatures
will remain cooler than normal through the week and into the
weekend.

&&

.DISCUSSION...As of 2:00 PM PST Monday...Widespread rainfall today
continues to shift farther to the south along with a frontal
system. Rainfall amounts have generally been running a bit ahead
of what was expected with even a few isolated locations getting
more than an inch. Urban areas generally picked up less than half
an inch.

Behind that band, colder more unstable conditions are taking shape
with showers and isolated thunderstorms now firing to our north-
northeast. That will work its way to the south through the evening
with convection possible over the eastern third of our CWA.
Additional amounts should be light, however small hail remains a
definite possibility.

Winds will also pick up tonight with 925 MB speeds expected to
exceed 40 KT over the North Bay. Forecast soundings show wind
direction fairly uniform from the surface to 500 MB increasing the
likelihood that the gusts will make it to the surface. A wind
advisory has been issued highlighting speeds up to 50 MPH.

Tuesday will feature very quiet weather as we will be between
systems. This is expected to be the only day in the work week with
dry conditions and lighter winds. Highs will be in the upper 50s
to the mid 60s. Clear skies and lighter winds will lead to cooler
conditions Tuesday night. Widespread 30s are forecast.

Main focus is now switching to late Wednesday through Thursday as
a moderate system will move across our region and bring another
round of widespread rainfall. Models are in fairly good agreement
that precipitation will return to the North Bay Wednesday
afternoon and then progress into the San Francisco Bay area that
evening. Rain will continue to work to the south and be across
Monterey Bay and Santa Clara valley starting Wednesday night. Rain
rates will increase leading to the main focus as the front goes
across Thursday morning. Moderate to heavy rain will be possible
along with gusty winds. Although IVT values are not that
impressive (still looking for a max around 500 kg/m/s), it is one
of the highest values from this season. For comparison, last year
we had several systems near or even exceeding 1000 kg/m/s. Rain
will switch over the showers behind the front. With a moist
unstable post-frontal flow in place, showers will continue
through Saturday. Rain amounts for the initial band through
Thursday are expected to range from 1/2" to 1.5" in most spots.
Higher values are possible along coastal ranges.

Wind speeds are still looking impressive with this system with
gusts over 40 mph possible as the front goes across. NAM 925 MB
values over the last few runs have been in very good agreement
depicting values to 45 KT associated with the front. Will look at
wind advisory potential tonight.

Next week is still shaping up to be dry at the start as a ridge of
high pressure builds from the Eastern Pacific to the BC coast.
&&

.AVIATION...as of 09:30 AM PST Monday...18Z TAFs. Main frontal
band has pushed through the SF Bay and continues to move south
through SJC and Monterey Peninsula. End of showers and clearing
behind the boundary will be abrupt with VFR conditions. Expect
some sct clouds later this afternoon as CU develops in unstable
atmosphere. The HRRR/Local WRF generate showers late this
afternoon/early evening. The chance is low and will VCSH these.
Clear skies developing late tonight/tomorrow.

Vicinity of KSFO...Improving conditions as skies clear from NW to
SE.  VFR this afternoon with breezy conditions.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Frontal passage to occur over the next
few hours with rain and low cigs. Clearing late this afternoon and
especially tonight.

&&

.MARINE...as of 09:29 AM PST Monday...A passing cold front will
bring rain and increasing northwest winds. Fresh seas will build
behind the front with gale force  winds over the waters north and
west of Point Reyes. Gusty northwest winds will continue through
midweek with another cold  trough dropping down the coast Thursday
and Friday producing  another round of gusty northwest winds,
building seas and periods of rain.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             GLW...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             GLW...Pt Arena to Pt Reyes 0-10 nm
             SCA...Mry Bay
             SCA...SF Bay

&&

PUBLIC FORECAST: Bell
AVIATION: MM
MARINE: MM

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea