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

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FXUS66 KMTR 281736

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1036 AM PDT Wed Oct 28 2020

.SYNOPSIS...High pressure will bring sunny, mild afternoons and
cool, clear nights through the remainder of the week. A slight
warming trend is then forecast this weekend with continued dry
weather conditions.

&& of 08:20 AM PDT Wednesday...Widespread min temps
in the upper 30s to low 40s F were observed this morning in the
interior valleys of the North Bay, with one station near Novato
measuring a min temp of 32 F just before dawn. Nonetheless, have not
observed widespread below-freezing temps this morning. Min temps in
the 40s F were also observed in the East Bay Hills, and the same can
be said for the Salinas Valley and other valleys along the Central
Coast. In terms of moisture, humidity recoveries have been
substantial regionwide, with several stations (particularly those in
the North Bay) observing values that are 35-50% higher than the
single digits and teens that were observed around this time
yesterday morning.

Winds have also been trending lighter across the CWA, with our
windiest peaks measuring much weaker overnight gusts than what was
observed 48 hours ago. Mt. St. Helena measured the strongest
overnight gust of 50 mph, but these winds did not mix down much
below 2500 ft. Elsewhere in the East Bay, Mt. Diablo peaked at 30mph
but again, very little of that mixed down below 1000 ft. It should
be stated that the SFO-WMC gradient is still around 9mb this morning
and is progged by the NAM to continue relaxing in the next couple of
days as the 588dm 500 hPA upper-level ridge becomes the dominating
synoptic feature for the region, and introduces slightly warmer max
temps through midweek.

From Previous Discussion...A general warming trend is forecast
through the remainder of the week as upper level high pressure
persists off of the California Coast. This will result in mostly
sunny daytime conditions with temperatures in the 70s to lower 80s
for most urban areas. Cool conditions are likely during the
overnight and early morning hours with the coldest interior
locations dropping in the the mid/upper 30s while most urban areas
cool into the 30s to lower 50s. There remains the potential for a
shallow marine layer to develop by late week which would bring
periods of low clouds to coastal areas during the late night and
early morning hours. Additionally, cloud cover in these areas will
hold temperatures up as well.

The upper level high over the eastern Pacific is then forecast to
shift inland this upcoming weekend resulting in a slight warming
trend. If this pattern holds true, look for more widespread 80s each
afternoon with continued dry weather conditions. The medium range
models indicate a mid/upper level trough approaching the West Coast
around November 3rd or 4th, yet confidence remains low for the
potential for rainfall across our region.

&& of 10:36 AM PDT Wednesday...For 18z tafs. VFR
conditions through the period as a predominately dry air mass
remains over the region. Profiler data shows a shallow marine
layer along the coast this morning at around 500 ft AGL. Continued
light offshore flow and dry conditions will likely prevent an
inland push of the marine layer tonight as well as suppress any
potential fog development. Light winds this morning turning
onshore this afternoon at about 10-15 kt.

Vicinity of KSFO...VFR through the period. Generally light winds
with increasing breezy onshore winds during the afternoon. A few
clouds present along the Pacific coast, though satellite shows
those currently dissipating.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR through the period. Light winds this
morning aside from locally breezy SE winds down the Salinas
Valley. Winds expected to turn onshore this afternoon.

&& of 08:50 AM PDT Wednesday...Winds will continue to
shift to a more southerly direction along the coast this morning,
but will remain generally light. Winds will shift back out of the
northwest by tomorrow. Mixed seas will persist through the period
with a pair of northwest swell trains in addition to a lighter
southerly swell and some weak wind waves.





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