Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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000
FXUS66 KMTR 192338
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
438 PM PDT Sun May 19 2019

.SYNOPSIS...Scattered showers through the afternoon and into the
evening hours. There is also a slight chance of thunderstorms
today. Dry weather will return late tonight and into Monday. A
cold system dropping in from the north will bring renewed shower
chances from Monday night through Tuesday evening. Drier weather
is forecast later in the week, but temperatures will remain cooler
than normal.

&&

.DISCUSSION...as of 01:38 PM PDT Sunday...Afternoon KMUX radar
imagery pretty much says it all - widely scattered showers and
thunderstorms across the Bay Area. The showers/thunderstorms are
thanks to an unstable atmosphere associated with a cold core upper
low. Cold upper low is also keeping temperatures below normal
this afternoon. In fact, many locations are currently running
10-20 degrees below normal for late May. Snow in the Sierra is not
that uncommon in May or June for that matter. Snow in May for the
Central Coast is definitely noteworthy. No official confirmation
yet, but observations show temps in the mid 30s (5k ft) and the Pt
Sur Profiler puts snow levels around 4,900 feet. Precip that
passes over the higher peaks above Big Sur could fall as snow or
rain/snow mix this afternoon.

For the rest of the day - scattered showers/thunderstorms will
continue this afternoon through early tonight as the upper low
slowly drifts southeast across the state. It will be a chilly
night across the Bay Area with lows in the 40s to lower 50s -
upper 30s higher peaks. Given the ample low level moisture
wouldn`t be surprised to see some patchy fog tomorrow morning.

A break in the action early Monday before another system will
bring precip chances back to the Bay Area Monday evening through
Tuesday. The tail end of a cold front will drop south across the
region bringing rain initially to the North Bay Monday evening
before moving south overnight and into Tuesday. Rainfall amounts
will be much less than the Sunday system - a few hundredths to a
quarter of an inch. Scattered showers will then linger Tuesday
into early Wednesday as the associated low pressure system move
southward. Not much in the way of QPF with the low pressure
either.

For the most part drier weather late Wednesday into early Friday
as the upper low moves farther inland toward the Desert
Southwest. A broad upper trough does remain over the region
keeping cooler/below normal weather in place. Precip chances
return again late in the week/next weekend as weak disturbance
rounds the base of the retrograding trough. Simply put, low
confidence, but precip chances will linger in the extended with
below normal temperatures.

&&

.AVIATION...as of 4:30 PM PDT Sunday...Scattered showers continue
over the area but the deep convection has shifted into the
Central Valley. Showers will diminish from north to south this
evening ending in the Bay Area after 06Z and the MRY Bay Area by
12Z. Plenty of low level moisture remains so we could see some
areas of MVFR cigs early Monday morning.

Vicinity of KSFO...Scattered showers through 06Z. Cigs expected
to remain above 5000 feet but could drop very briefly to 4000 feet
in showers. A lower level inversion layer will develop late
tonight which could bring 1500-2500 foot cigs after 12Z. West to
southwest winds to 15 kt decreasing after 06Z.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR conditions with cigs above 4000 feet.
Scattered showers will increase locally in the MRY Bay Area after
dark with cigs lowering into MVFR. Showers should end sometime
after 12Z but clearing not expected until midmorning.

&&

.MARINE...as of 04:17 PM PDT Sunday...Scattered showers will
remain a possibility this evening across  the coastal waters,
diminishing overnight. Swells will build  across the waters
creating hazardous conditions, particularly for  smaller vessels.
West to northwest winds will increase across the  waters into
Tuesday as another system passes by to the north.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             SCA...Rough Bar Advisory for SF Bar
             SCA...Mry Bay until 3 AM

&&

$$

PUBLIC FORECAST: MM
AVIATION: W Pi
MARINE: Sims

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