Hail and Lightning Strike in California, April 16, 2018

Area Forecast Discussion
National Weather Service San Francisco Bay Area
458 AM PDT Mon Apr 16 2018

.SYNOPSIS...Scattered showers and isolated thunderstorms will
remain possible over much of the region through this afternoon.
Dry and cool conditions are likely for Tuesday and into most of
Wednesday before a weak, fast-moving system pushes through the
region late Wednesday into early Thursday. A drying and warming
trend is then likely by late week.

&&

.DISCUSSION...as of 03:21 AM PDT Monday...An unseasonably cold
mid/upper level trough will to advect a much colder air mass in
over the region today. As a result, showers will likely increase
in coverage and intensity across much of the San Francisco Bay
Area and Central Coast through the morning and into the early
afternoon. With 500 MB temperatures forecast to drop as low as -33
deg C today, the atmosphere aloft will become increasingly
unstable. With this and increased surface CAPE by this afternoon,
isolated thunderstorms will also be possible over much of the
region. A few thunderstorms have already been detected offshore
and over the North Bay early this morning. Any thunderstorms that
do develop will likely produce brief heavy downpours, small hail,
cloud to surface lightning and locally gusty winds.

Snow levels are also forecast to drop to as low as 3,000 feet
through the day which would support some snow showers in the higher
elevations. Thus, a dusting of snow will be possible in the Bay Area
peaks with light accumulations possible in the Santa Lucia Mountains
of Monterey County (especially above 4,000 feet).

Additional rainfall amounts are likely to be around 0.10" to 0.25"
for most areas with locally higher amounts within any heavier
showers/thunderstorms that do develop. Shower activity is then
forecast to diminish by late this evening as the main trough axis
shifts inland to our east. As winds also diminish, look for colder
conditions region-wide tonight into Tuesday morning with lows in the
30s to middle 40s.

Dry, cool weather conditions are forecast for Tuesday and into most
of Wednesday ahead of another approaching system. This system is
forecast to move in from the northwest and bring light precipitation
to portions of the region from Wednesday night into early Thursday.
The quick moving system will only produce light rainfall amounts,
generally 0.10" or less with isolated amounts upwards of 0.25" along
the coastal ranges.

A ridge of high pressure is then likely to build back over the
region and along much of the West Coast by late in the week. This
will result in a warming and drying trend for the region from Friday
into the upcoming weekend. Look for temperatures to warm back to or
above seasonal averages by Saturday with widespread 70s to lower 80s
expected for inland areas. Dry weather conditions also appear likely
into the extended forecast period.

&&

.AVIATION...As of 4:58 AM PDT Monday...VFR/MVFR with scattered
showers and a slight chance of thunderstorms today. Low freezing
levels with cold upper level trough passing over northern California
today. Convection will dissipate by evening with VFR tonight, could
see a few patches of fog developing early Tuesday morning.

Vicinity of KSFO...VFR with MVFR cig at times today, lower cig mainly
with passing showers. Westerly wind gusts near 20 knots developing in
the afternoon

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR with MVFR possible at times today,
lower cig mainly accompanying passing showers.

&&

.MARINE...as of 3:21 AM PDT Monday...Chilly, showery weather with
a slight chance of thunderstorms will continue as an upper level
trough passes over northern California today. Northwest winds will
increase today. Winds will decrease Tuesday but another system
will arrive late Wednesday increasing winds again.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...SCA...Pt Arena to Pt Reyes 0-10 nm from 11 AM
             SCA...Pt Reyes to Pigeon Pt 0-10 nm from 11 AM
             SCA...Pigeon Pt to Pt Pinos 0-10 nm from 11 AM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 11 AM
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Mry Bay from 11 AM
             SCA...SF Bay from 3 PM

&&

PUBLIC FORECAST: RGass
AVIATION/MARINE: Canepa

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