Wildfire in California, July 4, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
917 AM PDT Fri Jul 4 2014

.Synopsis...
Little change today and Saturday with warming temperatures Sunday
and Monday. Monday will be the warmest day with highs 10 to 15
degrees above normal. A gradual cooling trend is forecast for the
rest of the week. There is a slight chance of thunderstorms over
the mountains Monday through Thursday.

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.Discussion...
Not looking at much change in the forecast. Dry conditions with
above normal daytime highs today into the weekend. Temperatures
at 9 am were generally similar to 24 hours ago or up to 5 degrees
warmer. It looks like Saturday should be fairly similar. But
once Sunday rolls around, high pressure over the 4 Corner region
will shift towards the west coast bringing widespread triple digit
heat to the Central Valley. Additional strengthening of the high
will increase temps again on Monday which is forecast to be the
hottest day of the week. Daytime highs on Monday will range 10-15
degrees above normal as several valley spots warm up between
104-110 degrees. Some monsoonal moisture could move into our
region starting Monday which could bring a slight chance of
thunderstorms to mountain regions.  JBB

.Previous Discussion...A weak weather system passing to the north will keep
onshore flow going over the north state today with stable
southwest flow aloft. Daytime highs today should come in similar
to Thursday or just a few degrees above normal for this time of
year. Little change is expected in the overall pattern on Saturday
with light to moderate onshore surface flow and stable southwest
flow aloft. The upper ridge of high pressure now over the great
basin will however begin to retrograde westward on Saturday
bringing a slight warm up in airmass. By Sunday...the axis of the
amplifying ridge is forecast to back to near the west coast. The
warming airmass and reduced onshore push will bring several
degrees of warming on Sunday. Forecast models put the ridge axis
directly over the CWA on Monday. Near maximum subsidence under the
ridge and a northerly gradient at the surface will bring still
more warming. Adiabatic warming over the Shasta Siskiyou mountains
will help push Northern Sacramento valley high temperatures close
to 110 degrees or about 15 degrees above normal on Monday. In
addition to the well above normal heat early next week...the other
weather feature to watch is the monsoon moisture forecast to begin
moving it's way northward into NORCAL early next week. Current
modeling has the higher precipitable water values still well south
of our forecast area Sunday afternoon. Have therefore removed
slight thunderstorm threat for the northern Sierra Sunday. By
Monday however...models push moisture plume northward up the coast
range with some instability showing up in this region as well.
Therefore...thunderstorm threat for the northern coastal range
still looks good for now. In coordination with Reno office...have
remove Cascade range and northern Sierra thunderstorm threat for
Monday where more stable conditions are indicated.

.Extended Discussion (Tuesday through Friday)

A gradual cooling trend is expected Tuesday through Friday of next
week as high pressure slowly weakens and shifts back eastward and
a more onshore surface flow returns. Each day next week will see a
few degrees of cooling as the upper ridge continues to slip
eastward. Subtropical mositure and instability being brought
northward in southeast flow aloft will bring a threat of afternoon
thunderstorms to most mountain aras Tuesday. By Wednesday...a
return to southwest flow aloft over the northwest corner of the
state should bring an end to the thunderstorm threat over the
coastal range. Southeast flow aloft over the Sierra Cascade range
will keep the threat going there. Thursday should be the last day
of Sierra crest thunderstorms as the upper flow becomes more
southerly. An upper trough moving into the eastern Pacific by
Friday will return stable southwest flow aloft to the region. This
will bring an end to any mountain thunderstorms and still cooler
daytime highs.

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.Aviation...

VFR conditions next 24 hours. SW winds 15-25 kts thru the Carquinez
Strait and Western Delta, otherwise mainly Southerly winds 10-15
kts in the valley.

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.STO Watches/Warnings/Advisories...
None.
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