Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Sacramento California
328 am PDT Thu Jul 24 2014
temperatures will rise to near normal today then continue to climb
slightly Friday and Saturday. Above normal temperatures will
continue through next week. The Sierra crest will see a threat of
thunderstorms Sunday through much of next week and possibly as
far north as the Shasta County mountains on Tuesday and Wednesday.
Short term discussion (today through saturday)...
an upper low pressure system over the Pacific northwest will lift
to the northeast today allowing high pressure to begin building
back over the western U.S. This will allow warming temperatures
today with daytime highs pushing upwards to near normal. At the
surface...high pressure will begin pushing into Oregon and
Washington creating an increased northerly surface gradient across
the north state. The current surface gradient from mfr to rdd is 8
mb and increasing breezy north winds have already begun in the
northern Sacramento Valley. This wind will likely increase later
this morning. Without upper level support however the increased
northerly winds will be somewhat spotty and not likely to become
especially strong. Fire concerns will increase however as relative humidity
values decrease considerably today compared to their elevated
values over the last several days under the influence of monsoonal
moisture. Overall airmass warms a bit more on Friday as upper
ridge over the southwest U.S. Begins to build back westward.
Lighter winds are expected on Friday as surface gradients relax
under the upper ridge. Still a bit more warming expected on
Saturday under the building ridge with daytime highs expected to
reach a few to several degrees above normal.
Mid range models consistently bring a weak trough into the north
coast on Sunday. The resulting more southerly flow aloft will
begin to bring monsoon moisture back northward. Although not as
significant as a moisture push as earlier this week...this surge
of moisture and instability may be enough for some isolated
afternoon or evening thunderstorms over the Sierra crest.
Otherwise...look for continued fair skies and daytime temperatures
Extended discussion (monday through thursday)
A ridge of high pressure will continue over the western US through
the extended period. Southerly flow aloft will keep some amount of
monsoon moisture over the region through the week. Stability progs
show slightly unstable conditions over the Sierra crest each day
Monday through Thursday. Combined with the monsoon moisture this
will create a threat of thunderstorms each day. Stability progs
show a slight instability over the northern mountains Tuesday and
Wednesday so the Shasta County mountains could see isolated
thunderstorms those days as well. Otherwise...fair skies and above
normal high temperatures will continue through the extended period
under the West Coast ridge.
VFR conditions expected the next 24 hours. Winds becoming
northerly at generally 5 to 15 kt after 15z. Gusts to 22 mph
possible over the western Sacramento Valley.