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Area forecast discussion 
National Weather Service San Francisco Bay area
447 PM PDT Thursday Jul 10 2014

Synopsis...an upper level low pressure off the coast will produce
a slight chance of late night thunderstorms over the extreme
northeast portions of the North Bay. Other than this tonight...typical Summer
weather can be expected through the work week with clouds
overnight giving way to mostly sunny conditions during the day for
most locations. High pressure will build back toward the area by
the weekend leading to a warming trend especially across inland
areas where hot weather will return.

&&

Discussion...as of 1:15 PM PDT Thursday...forecast focus today
continued on low end thunderstorm chances in the extreme northeast
portions of Napa County. As the upper low spins slowly towards the
coast tonight...and impulse lifting north around the low will help
provide some lift to act on middle level moisture. MUCAPE and tt
fields indicate at least a low end threat for thunderstorms across
northeast Napa County tonight...primarily after 09z /2 am PDT/.
The area remains on the southern edge of a very tight instability
gradient which will favor Sacramento area and points northward for
more significant thunderstorm development but given the favorable
parameters will mention this low end thunderstorm threat after
coordination with neighboring offices. Threat will end by around
sunrise Friday and the instability gradient lifts north out of the
area. The upper low and the shortwave trough responsible for this
will then lift back westward across the Pacific and heights will
ridge again across the area.

The rising heights will continue through the weekend as a 500 mb
high strengthens across southern Nevada. The upper low will
persist over the ocean and eventually lift northeast but at
present it looks like the ridging will win out over the area and
suppress the impacts of the low to extreme northern California by
late this weekend. After the trough clears the area just expecting
middle level ridging to dominate the pattern into early next week and
slowly weaken towards the end of the forecast period. Temperatures
will begin near to below normal and moderate to above normal
through the period as the ridging straightens. The hot spots in
the far interior will warm above 100 degrees again by this
weekend. Coastal temperatures will remain cool and locked in a typical
summertime regime.

&&

Aviation...as of 4:46 PM PDT Thursday...the weather pattern is
very similar to that of yesterday with a low pressure center
positioned just off of the coast maintaining southerly flow for
the area. This is resulting in gusty southerly winds at kmry and
an early stratus return for ksns. The southerly flow will also
keep stratus out of ksfo and the terminal through at least
midnight.

Vicinity of ksfo...VFR is expected to prevail through at least
midnight. MVFR ceilings are in the forecast beginning 0700z. First guess
for morning stratus burn off 1800z. Southwesterly winds 10 to 15 knots are
expected to prevail 0400z.

Confidence is moderate

Ksfo bridge approach...similar to ksfo.

Monterey Bay area terminals...VFR is anticipated at kmry through
0300z at which point MVFR ceilings are expected to return. Ksns is
currently reporting ovc014 so stratus has returned to the Salinas
terminal for the evening. Ceilings are expected to fall to ovc008 at
both terminals around midnight. Gusty southerly winds 15 knots
gusting to 20 are expected to prevail at kmry through early this
evening.

&&

Fire weather...
with an upper level low moving towards the area late tonight and
some moisture present above the surface...have included a slight
chance of thunderstorms in extreme northeast Napa County for
tonight. Chances will remain very low and so will not issue any
red flag warning products at this time but wanted to highlight
awareness to the low end threat of storms in a small portion of
the forecast area. After this threat tonight...warm and dry
weather returns with interior areas becoming hot again by the
weekend.

&&

Marine...as of 12:38 PM PDT Thursday...southerly flow will
continue along the central coast today as a low pressure system
remains over the eastern Pacific. Locally gusty winds will be
possible along the immediate coastline. Northwest winds will
return Saturday as the low moves north and high pressure builds
off the California waters.

&&
&&

Mtr watches/warnings/advisories...
... Bay north of the Bay Bridge until 11 PM

&&

$$

Public forecast: Johnson
aviation: Larry
marine: mm

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