FXUS66 KSTO 182026
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1226 PM PST Wed Dec 18 2024


.SYNOPSIS...
Dry weather and foggy mornings are expected through the remainder
of the week. First storm in a series of systems will move into
area Saturday followed by more systems into mid week next week
including Christmas.

.DISCUSSION...
Upper level riding and surface moisture will bring another chance
of fog tonight. Tonights chances look to extend well to the north
in the Sacramento Valley northward to Redding. HREF visibility
probabilities definately showing where low stratus would limit the
fog most likely from Northern San Jauquin Valley. Better chance of
fog with visibilites less than a half mile at 50% and above from
Sacramento north. Will be hoisting out a dense fog advisory for
this.

Fog not as certain Friday as we start to get under the influence
of first wave of a series of waves to move closer to the area and
shifting upper ridge a bit to the east.

Saturday...the first in a seris of AR systems will impact us.
Overall, this first wave shouldn't have many impacts. The main
push of energy from it will be further north as well as any cold
air aloft for instability. NBM QPF and probability forecast seem
reasonable. This system will definately be bringing more
precipitation to the northern half of the forecast area and will
also be pretty warm resulting in not too much snow impacts in the
Sierra. Probabilities of around 0.10 in the Sacramento area look
to be around 50% as in Redding probs of 1.00" around 50 percent.
As far as snow...snow levels they look to be around 7000 feet and
higher with amounts generally around 4 inches. Given this is a
weekend storm we will have to consider a snow advisory but given
expected amounts and level of it may not need any products for it.


.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)...

Not much change to the extended forecast which looks to be
unsettled with another...stronger compared to Saturday AR system
starting late Monday into Tuesday. AR tools suggesting a good
probability (above 50%) of system being moderate in strength when
it hits the coast but looks to decrease in strength as it moves
onshore. Precipitation amounts looking at NBM probabilities make
sense that it will be wetter but still not a super impactful
system with all things considered. Snow levels will be lower with
this second storm and given the timing...Christmas Eve into
Christmas overall impacts certainly higher then the first storm
this coming weekend on Saturday. That being said...snow levels
start very high above pass level and then should quickly drop
towards the end of the storm Tuesday night to around 5000
feet...which still isn't that low. NBM probabilities of a foot of
snow still modest below 40%. QPF amounts across the valley look to
be double that of the weaker Saturday with solid probabilites
(around 50%) of an inch in the north in Redding to only 25% of
that amount in the Sacramento area. Rasch

&&

.AVIATION...
Some lingering low stratus/BR/FG are producing MVFR conditions in
Southern Sacramento Valley through 23Z today. Some of the stratus
clouds may linger throughout the early evening. MVFR/IFR
conditions and areas of LIFR conditions in BR/FG with stratus
clouds are then expected to return after 04Z Thursday. Surface
winds are generally below 12 knots, with diurnal wind pattern.
Winds gusting to 20 knots in the higher Sierra elevations.

&&

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

$$