Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
1119 PM PDT Thursday Jul 2 2015
Synopsis...showers and isolated thunderstorms will remain a
slight possibility this evening...mainly across the north and
East Bay. Otherwise dry weather is forecast through the Holiday
weekend and into next week...along with a gradual cooling trend.
Discussion...as of 9:15 PM PDT Thursday...00z Oak sounding shows
a continued moist southeasterly flow aloft with a precipitable water value at
1.37 inches. Within this moist flow isolated light showers
continue to move from east to west across our region...producing
nothing more than a few sprinkles. Radar currently shows an area
of more widespread shower activity over the southern Sacramento
Valley and SAC Delta area...associated with a shortwave trough
currently moving from east to west across north-central California.
This shower activity has the potential to produce some measurable
precipitation across the North Bay and northern portions of the
East Bay late this evening. Thunderstorms have been almost
entirely confined to the Sierra today and it appears unlikely that
we will see any thunderstorms in our area...but will leave the
slight chance in for the North Bay and portions of the East Bay
through the evening.
Meanwhile...the marine layer is becoming better established along
the coast and is quite shallow this evening...resulting in patchy
dense fog near the ocean from San Mateo County south to Monterey
County. A forecast update earlier this evening included the
addition of patchy dense evening coastal fog.
The middle/upper levels are forecast to become drier tomorrow and
into the weekend as the upper low offshore lifts north and the
flow aloft veers from southeast to south. Thus...precipitation
chances will end by tomorrow and we can expect dry weather
through the Holiday weekend. In addition...the upper ridge over
northern California will continue to weaken over the next few
days...resulting in a deeper marine layer and a gradual cooling
trend. Some inland valley locations saw their high temperatures
drop by 10 to 15 degrees from yesterday to today. The cooling
trend through the weekend is expected to be more gradual. Gradual
cooling is then expected to continue through much of next week as
the upper low offshore slowly approaches the northern California coast.
Aviation...as of 11:19 PM PDT Thursday...for 06z tafs. Mixed bag
overnight with area of virga showers over the North Bay shifting
north and west over the ocean. Low ceilings now showing up at koak and
Monterey Bay terminals and will likely last through 16-17z Friday.
Vicinity of ksfo...mainly high clouds impacting ksfo but low
clouds are nearby and cant rule out some low ceilings by sunrise but
thats still low confidence. Finger of fog may just stay pointed
over koak. Higher confidence that given the shallow nature of the
marine cloud deck that any low ceilings will mix out between 16-17z.
Ksfo bridge approach...similar to ksfo.
Monterey Bay area terminals...low ceilings are in for the night at
kmry and ksns and will mix out by 17z Friday.
Marine...as of 11:19 PM PDT Thursday...high pressure over the
interior and a trough near the coast will create a prolonged
period of light wind and seas across the coastal waters through
the Holiday weekend.
Public forecast: dykema
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