Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Sacramento California
357 am PDT Monday Jul 6 2015
cooler this week with daily afternoon and evening thunderstorms
mainly over the mountains. Thunderstorm coverage may increase over
the mountains...SAC valley and surrounding foothills later Tuesday
through Thursday as an upper low over the eastern Pacific moves
across the region.
mostly clear skies across interior norcal early this morning. Some
middle and upper clouds are present at times over the northern Sierra
and northern mountains. Onshore flow continues and the marine
layer remains around 2500 feet deep. This along with lower temperature/deep
spreads may result in some stratus making it inland into the SAC
region early this morning. Temperatures are mostly slightly
cooler compared to 24 hours ago and range from the upper 50s to
upper 70s in the Central Valley to the 50s and 60s in the
Little change is expected across the region today as most
thunderstorm activity this afternoon will again be along or east
of the northern Sierra crest. Temperatures will cool a bit
further in most areas with onshore flow continuing.
Bigger changes develop across the area Tuesday through Thursday as
the low over the eastern Pacific moves slowly eastward and
eventually inland across central California later Wednesday into
Thursday. More widespread clouds along with cooler temperatures
are expected as the airmass cools and middle and upper level moisture
continues to circulate across the region.
While showers and thunderstorms will remain most likely over
higher terrain, elevated instability may be enough to sustain some
storms propagating off the higher terrain into the Central Valley
starting Tuesday. A better chance of more widespread showers and
thunderstorms will be possible Wednesday and Thursday as dynamics
associated with the low may come into play.
Extended discussion (friday through monday)...
GFS and ec models have the closed low weakening on Friday into an
open trough before moving out of the region by the end of the day.
However, a broader synoptic trough pattern quickly follows in its
wake. This secondary trough will linger over the West Coast over
the weekend. The axis of this trough will reside just offshore
through the extended keeping our region sandwiched between that
trough and high pressure over the Desert Southwest.
For Friday and Saturday, the chance of mountain thunderstorms will
persist and may also impact the northern Sacramento Valley on
Friday. By Sunday, the desert SW high pressure cell will
strengthen and build into our region causing a warming trend with
dry weather. Throughout the extended, daytime highs will start off
5-8 degrees below normal and then gradually warm up to normal by
VFR conditions continue, except local MVFR/IFR near the Delta as
marine stratus returns. South winds 8-15 knots in the Sacramento
Valley (nw in the San Joaquin valley) will continue, with SW wind
gusts 25-35 knots near the Delta. Dang/jbb