Weather Service Report

FXUS66 KSTO 282245

245 PM PST Wed Jan 28 2015

Dry weather expected into the weekend with night and morning
valley fog and above normal temperatures. Some breezy wind
possible Friday into Saturday. Mostly dry weather likely to
continue into early next week.

Satellite imagery showing thin cirrus over Interior NorCal while
fog and low clouds in the CWA have eroded away. Cooling cloud tops
seen on IR off the Northern California coast with some cu/tcu
along the coastal range. This in response to increased UVM and
instability with approaching upper trough. Considerable mid to
high cloudiness also located just to the south of the forecast
area with some of this likely to spread into southern portions of
the forecast area tonight. Despite this, expect fog and low clouds
to redevelop in the Northern San Joaquin valley later tonight and
expand northward into the Sacramento valley overnight into
Thursday morning.

Associated dynamics/instability and moisture look less with latest
model runs as the upper trough shifts through Thursday. Thus have
removed mention of precip from our forecast portion of the Sierra
Nevada for tomorrow afternoon. Main impact will be some higher
level cloudiness. High temperatures Thursday expected to be
similar to today.

Closed upper low develops over SoCal Friday as EPAC upper ridging 
builds into the PacNW. At surface, inverted trough extends through 
CA into OR as surface high builds into the the Great Basin. This 
pattern will result in some breezy N to E winds over Interior NorCal 
Friday. This will help limit valley fog development and allow for 
faster clearing for areas that have some.

Upper ridging builds into NorCal over the weekend with locally 
breezy wind again Saturday. Night and morning valley fog and low 
clouds expected to continue and possibly be more widespread under 
increased subsidence. Above normal temperatures continue over the 
weekend with upper 50s to around 70 in the Central Valley with 
mainly 50s to 60s elsewhere.



.Extended Discussion (Sunday through Wednesday)

Ridge flattens Sunday into Monday with the potential for some
disturbances moving through. This will bring a threat of
precipitation to interior Northern California, especially on
Monday. A few models now suggesting more amplitude in ridge which
would lead to a farther north storm track and lower precip
chances. If this trend continues precip chances will need to be
lowered in the next few forecast packages. No significant
precipitation is expected through the extended. High pressure
ridge builds over the Eastern Pacific Tuesday then moves over the
west coast on Wednesday bringing drier weather. Fog and low clouds
are expected in the morning in the Valley. Beyond the
extended...long range models indicate a possible pattern change to
wetter weather beginning around Feb 7th. Stay tuned. 



Predominant VFR conditions this afternoon across interior NorCal.
Expect some MVFR/IFR with local LIFR conditions to develop south
of KMYV between 6-18z tonight. Generally light northerly winds
continue across Valley TAF sites.



.STO Watches/Warnings/Advisories...


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