Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 241718
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1018 AM PDT Thu Jul 24 2014
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 Sunday)...
An upper low pressure system is swinging through the PacNW this
morning while warming high pressure begins building northward
over the western US. North winds have been increasing to 10 to 15
kts gusting to 25 kts in the northern Sac Vally this morning with
a MFR to RDD surface pressure gradient of around 9 mb. Though
upper level support is diminishing as the low lifts northeastward,
surface gradients are expected to peak this morning and early
afternoon before decreasing by this afternoon/evening.
Temperatures are already running 4 to 10 degrees warmer than this
time yesterday due to the warmer air mass and north winds. Shen
Fire concerns will increase however as RH 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 with gusts to 25 kts possible
over the western Sacramento valley.