FXUS66 KMTR 190549

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1049 PM PDT Thu Oct 18 2018

.SYNOPSIS...A slight warming trend is forecast through the upcoming
weekend as high pressure builds over the region. Dry weather
conditions are also likely to prevail through the weekend. A pattern
change will result in cooling conditions early next week that will
persist through late week with a slight chance of precipitation
developing over the North Bay.


.DISCUSSION...as of 08:48 PM PDT Thursday...The marine layer
remains at around 1000 ft per the Fort Ord Profiler. Satellite
imagery shows stratus offshore as well as patches of low clouds
developing around Point Reyes, along the San Mateo coast, and
around the Monterey Peninsula. Expecting similar, if not less,
cloud coverage overnight tonight than was seen this morning.
Temperatures this evening are a few degrees warmer than this time
yesterday as high pressure builds across the region and onshore
flow has slightly lessened.

No changes made to the forecast this evening. A warming trend is
expected tomorrow and Saturday as onshore flow weakens and a ridge
of high pressure builds over the region. Lingering offshore winds
aloft will allow for warming to reach the coast as well. Expect
highs tomorrow in the 60s to 70s at the coast with some 70s and
more widespread 80s inland. Isolated interior locations may
approach 90 deg F. As high pressure builds over the region and
weak offshore flow aloft remains, the marine layer is forecast to
compress into the weekend. Therefore, expect less overnight and
morning low cloud coverage. Some low clouds may still form along
the coast and around San Francisco.

The upper ridge will then move further inland late this weekend
and into next week allowing for some cooling. Models still show an
upper trough approaching the region early next week. This would
bring widespread cooling and increasing cloud cover as the marine
layer expands. Many locations could see afternoon high
temperatures at or even a few degrees below seasonal normals by
Monday. Disagreement remains among forecast models as to the
possibility of precipitation Tuesday through Friday. The GFS
shows rainfall chances further south into the North Bay on
Wednesday with a moist flow into Northern California. The ECMWF
has been trending drier, keeping precipitation well to the north
of our area. Will need to see if there is more consistency with
upcoming model runs. Whether or not we see any precipitation,
temperatures are forecast to cool next week to near or below
seasonal averages. Chances of precipitation will continue to be
monitored as the event nears.


.AVIATION...as of 10:30 PM PDT Thursday...Marine layer has
compressed down to around 1000 feet this evening. Northerly
gradient has increased which will delay the stratus from
spreading inland and may keep it out completely if the latest
model guidance verifies. For now will delay the timing of cigs and
see how much the stratus spreads inland.

Vicinity of KSFO...VFR is expected through 13Z. Becoming MVFR from
13Z-17Z but confidence is low as latest model guidance has backed
off on the amount of stratus.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...Stratus over southern MRY Bay extends
into SNS. Stratus has stopped just north of KMRY but should be in
after 08Z. IFR cigs clearing after 17Z.


.MARINE...as of 10:34 PM PDT Thursday...A 1024 mb high centered
350 miles west of Point Arena will slowly weaken over the weekend.
This will keep light northwest winds over the coastal waters.





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