Rip Current in California, May 13, 2019

Area Forecast Discussion
National Weather Service San Francisco Bay Area
249 PM PDT Mon May 13 2019

.SYNOPSIS...Generally dry weather conditions are forecast to
continue through Tuesday with periods of night/morning low clouds and
patchy coastal drizzle. An unseasonably wet weather pattern is
forecast to develop by midweek and potentially continue to early
next week with widespread rainfall likely.

&&

.DISCUSSION...as of 02:49 PM PDT Monday...Mostly sunny conditions
have developed over inland areas this afternoon with temperatures
generally in the 60s coast to 70s inland. Coastal stratus
continues along the immediate coastline with some locations still
in the 50s. Look for the marine layer to deepen through the night
with more widespread coastal/valley cloud cover heading into
Tuesday morning.

Slight cooling is likely region-wide on Tuesday in advance of an
approaching mid/upper level trough. In advance of the trough, a
deeper plume of atmospheric moisture will begin to advect inland
across northern California on Tuesday. Atmospheric river forecast
products are suggesting this system will be a weak event, rather
uncommon for the month of May. PWAT values in excess of 1.00" and as
much as 1.25" will then shift southward into the region as a weak
frontal boundary sags southward Tuesday night into Wednesday. This
will allow for light rain to develop over the North Bay as early as
late Tuesday night before increasing in coverage and intensity
Wednesday morning. The boundary will continue to shift southward
down the coast resulting in widespread rainfall region-wide through
the day Wednesday and into Wednesday night. Moderate to locally
rainfall will be possible Wednesday night into early Thursday
morning as a stronger vort max swings through the base of the upper
level trough and pushes inland across the region. Rain is forecast
to change over to rain showers by Thursday morning when there will
also be the potential for isolated thunderstorms as the core of the
disturbance moves inland. Showers will diminish in coverage Thursday
night into Friday as a weak short-wave ridge develops over the
region.

Rainfall totals during the second half of the week are forecast to
range from 0.50" to 1.00" in most urban areas (lesser amounts in the
rain shadowed valleys and typically drier spots) to as much as
2.00" in the coastal ranges and North Bay Mountains. Breezy to
locally gusty southerly winds will also develop ahead of the
approaching system Wednesday night into Thursday. While this system
is forecast to be rather strong for this time of year, widespread
damaging winds and flooding do not appear likely at this time.

Unsettled weather conditions appear likely to continue into the
weekend and even into early next week as a series of storm systems
push inland across the region. This will keep daytime temperatures
below seasonal averages with periods of wet weather conditions.
Ensemble mean rainfall during the next 7 to 10 days could range from
2.00 to 2.50" for some urban locations, definitely uncommon for mid
May. Folks are urged to continue to monitor the forecast in the
coming days for additional details as we move into an unseasonably
wet weather pattern.

&&

.AVIATION...as of 10:40 AM PDT Monday...For 18z TAFs. Slow eroding
marine layer is complicated matters this morning with continued
onshore flow. Interior terminals are now VFR and coastal/Bay
terminals are transitioning to VFR. Do expect mostly VFR through
this afternoon with an early return of stratus this evening.
Marine layer is on track to deepen tonight so coverage of clouds
will be greater. Burn off of low cigs will be later on Tuesday
morning.

Vicinity of KSFO...SFO continues to be on the edge of clouds this
morning with solid cigs NW and SKC to SE. Expect this to be the
case for much of the afternoon given the onshore flow. Will
forecast SCT in TAF, but obs may say BKN at times. Early return of
cigs tonight.

SFO Bridge Approach...VFR with clouds confined to runways
northward.

Monterey Bay Terminals...VFR this afternoon. MRY may occasionally
see a passing cig or two. Early return of cigs this evening.

&&

.MARINE...as of 08:55 AM PDT Monday...High pressure located off
the coast of Southern California will maintain light to moderate
northerly winds over the waters. Winds will be locally strong
south of Pigeon Point along the coast. An approaching late season
storm will bring unsettled weather as well as southerly winds to
the coastal waters Tuesday and Wednesday. Westerly winds will
return to the region by Thursday. A combination of a long period
SW swell and a short period wind waves will continue to move
across the coastal waters through the first half of the week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...SF Bay until 9 PM
             SCA...Mry Bay until 9 PM
             SCA...Pigeon Pt to Pt Pinos 0-10 nm until 9 PM
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM

&&

PUBLIC FORECAST: RGass
AVIATION: CW
MARINE: MM

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