000
FXUS66 KSTO 251043
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
343 AM PDT Sat Sep 25 2021



.SYNOPSIS...
A cooling trend through early next week with shower chances late
Monday into Tuesday, especially over the mountains. Breezy
mountain winds possible during the afternoon hours through Monday.

&&

.DISCUSSION...

Upper ridge that has brought the warm weather this past week will
flatten today, as troughs begin to impact the Pacific Northwest.
This will initiate a Delta breeze with a cooling trend over the
weekend. Afternoon high temperatures today will fall into the
upper 80`s to low 90`s, which is about a 10 degree cool down from
the past few days. Larger trough will deepen along the West Coast
Monday with showers spreading over the Coast Range through the
day. Showers will then spread over much of the Northern Sacramento
Valley and Sierra Monday night. Precipitation amounts look to be
on the light side with Valley amounts generally less than 0.25 and
mountain amounts less than 0.50 inches. Further cooling into the
80`s Sunday and Monday then 70`s Tuesday with increasing onshore
flow. Winds through the Delta could gust up to 35 mph at times
into next week.

Brief periods of breezy ridgetop winds will be possible during the
afternoon hours through Monday ahead of the trough. This could
bring elevated fire weather conditions for a few hours, but
increasing relative humidity levels each day will diminish the
concern.


.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...

Models similar in EPAC upper ridge building inland over NorCal
Wednesday behind exiting system. Ridge axis shifts through
Wednesday night into Thursday as next Pacific frontal system
approaches. Front weakens as it moves into the PacNW Thursday
and associated precip remains north of our CWA. Associated upper
trough follows Friday. Oper GFS closes trough off the CA coast
while EC and ensembles support a more progressive and drier
solution. Below normal high temperatures expected through the
extended forecast period.


&&

.AVIATION...

VFR conds ovr intr NorCal nxt 24 hrs. Sfc wnd genly AOB 12 kts exc
vcnty of Delta and ovr hyr mtn trrn aftns into eves with lcl gusts
to 25 kts poss.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$