NWS Forecast Area Discussion - San Francisco Area

FXUS66 KMTR 192351

Area Forecast Discussion
National Weather Service San Francisco Bay Area
451 PM PDT Thu Apr 19 2018

.SYNOPSIS...A warming trend and dry weather conditions are
forecast into the upcoming weekend. A weak cutoff low approaches
the region mid to late next week.

&& of 03:00 PM PDT Thursday... The 550dm 500mb upper
low that brought cloudy skies and cooler temperatures yesterday
and into this morning has now eased eastward into the Great
Basin. High pressure from the eastern Pacific is now building
towards the California coast and will begin to move ashore later
today. Daytime temperatures reflect this shift in air mass,
starting 5 to 10 degrees cooler than yesterday this morning, but
lastest observations are 5 to 10 degrees warmer than yesterday
afternoon. A moderate northerly gradient has set up in between
these two features and is strongest along the coast (3.7mb ACV-
SFO/3.1mb SFO-SBA), resulting in breezy winds regionwide and local
gusts up to 40 mph (mainly along the coast). Winds are forecast to
ease in the coming days as high pressure builds in and the
gradients weaken.

Fair weather conditions are expected through the weekend and into
early next week.  A slight warming trend is forecast now through
the weekend where temperatures will rise to a few degrees above
normal at the coast (mid to upper 60s) and up to 10 degrees warmer
than normal farther inland (upper 70s to low 80s). A weak upper
trough passes to the north on Sunday which may limit the warming
trend over the San Francisco Bay area, however, the the warming
trend for the Monterey Bay area will not be impacted. Fair weather
conditions persist for Monday and into Tuesday.

The GFS EURO and Canadian models show a 556-562dm 500mb cut off
low near California mid week next week, but model output varies
widely on the positioning and trajectory of this feature. The
Canadian shows the upper low over NorCal by Wednesday morning, the
EURO brings the low ashore Thursday morning closer to the Big Sur
coast, and the GFS doesnt bring the upper low ashore until next
weekend, mainly from Big Sur to SoCal. None of these scenarios
should bring much precipitation to the area, instead, any
precipitation should be light and spotty, primarily in the form of
wrap around showers in the wake of any frontal passage. This storm
system should come into better focus as the model output begins to
align on a solution. Until then, confidence remains low.


.AVIATION...As of 4:52 PM PDT Thursday...For 00z tafs. Patchy low
clouds across area hill this afternoon will dissipate this evening
after sunset. Patchy low clouds will return to KMRY and KSNS after
a temporary clearing this afternoon. Elsewhere mainly clear skies
expected. Gusty onshore flow will persist through late this
afternoon and ease after sunset.

Confidence is moderate to low with respect to overnight cigs.

Vicinity of KSFO...VFR will prevail through the forecast period.
Afternoon west winds to around 20 kt, with gusts over 25 knots
will ease after 04z.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...MVFR cigs anticpated to return to KMRY
around 04z this evening. KSNS is anticipated to see temporary
clearing with cigs also returning around 04z. Gusty west winds
around 15 kt with gusty to around 25 kt expected through this
afternoon. Winds will ease this evening.

&& of 2:49 PM PDT Thursday...High pressure over the
eastern Pacific will maintain breezy/gusty NW winds through Friday
and into the weekend. As a result, the strong winds will generate
steep wind waves and fresh swell, causing hazardous seas through
much of the weekend.


     .Tngt...SCA...Pigeon Pt to Pt Pinos 0-10 nm
             SCA...Pt Arena to Pt Reyes 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...Pt Reyes to Pigeon Pt 0-10 nm
             SCA...Mry Bay until 3 AM




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NWS MTR Office Area Forecast Discussion