FXUS66 KSTO 032125
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
125 PM PST Tue Dec 3 2024

.SYNOPSIS...
Areas of low elevation morning fog persist through much of the 
week ahead alongside otherwise dry and gradually warming weather. 

.DISCUSSION...
Residents in the central/southern Sacramento Valley and northern
San Joaquin Valley awoke to patchy fog once again this morning,
with visibilities getting as low as 0.50 miles at KSMF. At the
time of this writing, most of the fog has lifted out of the area,
however there are still some areas of patchy fog/haze present.
KSCK is reporting visibilities of 4.0 miles with hazy conditions
present, and KSMF is at 6.0 miles with haze. Skies are expected to
clear further into the afternoon, which will once again allow for
radiative cooling to affect the Valley floor tonight and bring
another round of patchy fog. The HREF suggests around a 20-50%
chance of visibilities less than 0.25 miles tomorrow AM from
around Chico south into Modesto, with the higher chances in the
northern San Joaquin Valley. Remember to allow yourself more time
for the morning commute tomorrow, especially if your commute is
along portions of I-5, I-80, CA-99, I-205, and local roadways in
the aforementioned areas.

Latest ensemble guidance continues to portray a rather stagnant 
upper level pattern, with ridging dominating the synoptic regime.
A weak upper level low will develop near Baja California tomorrow
and translate into the Four Corners region later in the week,
while an EPAC high will develop and keep NorCal dry and clear,
except for any morning fog that develops. High temperatures are
forecast to remain in the low to mid 60s for the Valley for the
remainder of the work week, with the northern Sacramento Valley
including Redding and Red Bluff could reach 70 by Thursday and
Friday. Light north to east winds will continue in this stagnant
weather pattern, although fire weather concerns remain low due to
recent rains/snow. Breezier winds of 25 mph will be possible in
the foothills and mountains, especially in drainage basins, during
the overnight and early morning hours. 

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...
As we move into the weekend, ensembles continue to paint an 
amplified ridge axis orientated west to east translating eastward 
and a weak shortwave trough ejecting out of the Pacific Northwest.
Ensembles are differing on the trajectory of this trough right 
now, where the ECMWF keeps the area mostly dry and the GEFS 
introduces some precipitation chances for the far northern 
Sacramento Valley. Whether the trough slips further east or takes 
a more westerly track will ultimately decide if there are any 
precipitation impacts, however temperatures will fall slightly as 
a result of lowering heights aloft. The NBM has started to pick up
on the more westerly/southerly track and is introducing slight 
(10-15%) chances of precipitation in northern Shasta County, north
of Redding proper. Another potential concern would be periods of 
gusty northerly winds developing Sunday through Monday morning. 
Best chances of gusty winds 25 mph+ will reside along the I-5 
corridor and into the Delta. 

&&

.AVIATION...

Areas of MVFR/IFR conditions with isolated LIFR conditions from 
fog and BR are possible in the Southern Sacramento and Northern 
San Joaquin Valleys by 03Z Wednesday until around 18Z Wednesday. 
Otherwise, VFR conditions continue for the next 24 hours for 
Interior Northern California. Surface winds are forecast to remain
mainly below 12 knots, except for local northeast wind gusts 
20-25 knots in the Sierra/foothills from 03Z to 18Z Wednesday. 

&&

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

$$