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

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FXUS66 KMTR 202348
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco Bay Area
448 PM PDT Thu Sep 20 2018

.SYNOPSIS...A warming and drying trend continues today due to offshore
flow. Temperatures are expected to cool slightly over the
upcoming weekend but will remain slightly above seasonal averages.
A renewed warming trend is then possible during the first half of
next week as high pressure builds near the West Coast and offshore
flow returns.

&&

.DISCUSSION...As of 12:47 PM PDT Thursday...Under sunny skies,
area temperatures are really warming up across the district.
Stations in the east Bay Valleys are running mainly in the mid
80s, roughly 10 degrees warmer than yesterday at this time. Some
places closer to the coast area also running much warmer,
including Salinas Airport, which is 80 degrees, and even downtown
San Francisco has warmed to 79 degrees! Monterey is still on the
cool side, registering in the middle 60s.

Wind speeds continue to decrease across the higher terrain.
Latest RAWS readings show gusts in the 10-20 mph range last hour
in both the North Bay and East Bay mountains. Wind speeds are a
little lighter in the Santa Cruz mountains, but Relative Humidity
readings are low - in the mid teens to mid 20s. The Red Flag
Warning remains in effect until 5 pm.

Skies should continue to be clear overnight. Models indicate a
"southerly surge" or at least a wind shift occuring along the
coast by Friday morning. However, right now, satellite imagery
shows coastal stratus still south of Point Conception. Expect
stratus to increase over the coastal waters at least by Saturday
as an upper level trough approaches the Pacific Northwest. We
should also see a cooling trend as this trough moves through.

High pressure aloft is then forecast to rebuild over the Eastern
Pacific early next week. This will bring in warmer temperatures
once again beginning early next week with warmest inland areas
seeing highs in the 90s. There could be episodes of offshore flow
night and morning hours as a surface high develops over the Great
Basin.

&&

.AVIATION...As of 4:30 PM PDT Thursday...Warm offshore flow over
the area. While the winds have diminished the airmass remains dry.
VFR conditions will persist through at least Friday morning.
Southerly flow develops along the coast Friday which may start to
push stratus up the coast from southern California. Does not look
like it right now as there is little stratus along the southern
California coast.

Vicinity of KSFO...VFR. West to northwest winds to 15 kt through
04Z.

SFO Bridge Approach....Similar to SFO.

Monterey Bay Terminals....VFR.

&&

.FIRE WEATHER...As of 9:00 AM PDT Thursday...High pressure to the
north of the district resulted in locally gusty northerly winds
and drier air in the hills and mountains overnight. Winds were
strongest over the highest terrain of far northern Sonoma and
Napa counties. Northerly winds in the hills and mountains have
started to decrease and will continue to do so today. A Red Flag
Warning is in effect for the North Bay Mountains, East Bay Hills
and Diablo Range, and Santa Cruz Mountains until 5 pm today.

Winds will continue to decrease in the afternoon, but the air
mass will remain very dry in the hills and mountains tonight into
Friday.

Slightly cooler conditions are forecast over the weekend, but a
renewed warming and offshore flow is possible during the first
half of next week especially if high pressure strengthens into the
Great Basin.

&&

.MARINE...as of 04:30 PM PDT Thursday...High pressure over the
eastern Pacific and a thermal trough along the coast will resulted
in continued breezy to gusty northwesterly winds. These winds will
produce steep waves over the northern offshore waters as well.
Winds will then diminish on Friday as high pressure weakens.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 9 PM
             SCA...Pt Arena to Pigeon Pt 10-60 nm

&&

$$

PUBLIC FORECAST: Sims
AVIATION: W Pi
MARINE: RGass
FIRE WEATHER: Canepa/Sims

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