NWS Forecast Area Discussion - San Francisco Area

FXUS66 KMTR 200525

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1025 PM PDT Fri Oct 19 2018

.SYNOPSIS...Sunny and warm with a only a few degrees of cooling
through the weekend. More noted cooling to return early next week
as fronts pass to our north with increasing onshore flow and a
cooling airmass. Any light rain from these fronts will likely
stay north of Sonoma county next week while high pressure builds
over southern and Central California by the second half.

&& of 9:00 PM PDT Friday...High pressure ridging
across the Pacific Northwest coupled with a thermal trough along
the coast brought clear skies and light offshore flow to the
forecast area today. Afternoon highs rose anywhere from a couple
of degrees along the coast to as much as 11 degrees inland
finishing well above normal for this time of year. Coastal area
reached into the 60s with mid to upper 70s around the Bay. Inland
areas reached well into the 80s with a few 90s over the warmest
inland areas.

Latest satellite imagery depicts mainly clear skies across inland
areas this evening with widespread low clouds spread across the
coastal waters from the California/Oregon border to south of
Pigeon Point. As the night progresses low clouds will fill in
along the coast and locally inland through coastal gaps and
valleys with patchy dense fog possible. The marine layer stands at
approximately 800 feet at this hour with little change expected.
High pressure ridging across Northern California and into the
Great Basin will maintain a compressed marine layer and as well as
light offshore flow. The combination of the two will keep status
confined mainly to the coast with limited inland intrusion
overnight. The gradient from WMC to SFO continues to trend
stronger and is currently 9.5 MB while the onshore gradient from
SFO to SAC remains weak at 0.5 MB.

The forecast remains on track. No updated expected.

From previous discussion...The upper level high pressure ridge
over California will maintain warm conditions through Saturday
with a gradual cooling trend beginning on Sunday and persisting
through midweek as low pressure systems move across the Pacific
Northwest. Latest model guidance keeps all rain chances north of
our CWA through the forecast period, though.

Another ridge is forecast to approach California from the Eastern
Pacific late in the week ushering in another warming trend by next
weekend. The latest run of the ECMWF hints at another upper
trough possibly affecting Northern California by the end of the
month...we`ll see, although climatologically, this timing checks

&& of 10:25 PM PDT Friday...For 06z tafs. A shallow
marine layer remains in place as satellite imagery shows low
clouds along the coast beginning to move inland locally. VFR
conditions forecast through the period at this time aside from
patchy fog in the North Bay. Some localized intrusion of low
clouds along the coast may occur and briefly cause MVFR/IFR cigs
at coastal terminals. Satellite will be monitored and tafs will be
amended as needed.

Vicinity of KSFO...VFR with some patchy low clouds possible early
tomorrow morning.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR. Patchy low ceilings may return into
tomorrow morning.

&& of 08:11 PM PDT Friday...Generally light to locally
breezy northwesterly winds will continue as high pressure over the
Great Basin and the eastern Pacific weakens heading into next
week. Mixed moderate period northwest and southerly swell will
persist before a longer period southerly swell arrives early next





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NWS MTR Office Area Forecast Discussion