Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 231844
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1044 AM PST Thu Nov 23 2017


.SYNOPSIS...
Mild temperatures this week with a weak weather system today.
More widespread rain spreads south Saturday into Sunday followed
by a colder system early next week.

&&
Mostly cloudy across much of the area this morning, with some
light, scattered precipitation having fallen from around
Wheatland northward. Totals have ranged from a trace to
0.04"(Redding) in the Valley, to up to 0.14" at Manzanita Lake
and Mineral in the mountains of western Plumas County. The band of
light precipitation is currently over the Paradise area, and is
projected to slide southward through the day, reaching the I80
corridor and Sacramento metro area around 1-2 pm this afternoon.

Cloud cover limited morning Valley fog development, and the
patchy fog that formed has quickly dispersed. Areas in the
northern San Joaquin have been south of the main cloud deck and
have warmed quickly. At 10 am, Stockton was already 65, Modesto
66. Increasing clouds should limit further increases, though highs
should reach the low to mid 70s there. Most other Valley
locations should remain in the upper 60s, which is still several
degrees above the daily average highs of around 60. Forecast is on
track, no updates made. EK

.PREVIOUS DISCUSSION... Plenty of cloud cover continues to stream
up from the southwest early this morning and some spotty light
precipitation has been occurring over the northern half of the
forecast area overnight along a weak frontal boundary. The cloud
cover has inhibited dense fog development, but surface
observations in the valley are saturated (or nearly so) so some
patchy fog and stratus will be possible thru the morning. Current
temperatures are milder compared to 24 hours ago and range from
the mid 30s in the mountain valleys to the upper 40s and 50s
elsewhere.

Deep moisture plume with TPW of 1.25 to 1.5 inches continues to
feed into NorCal from the southwest as the upper ridge retreats
slightly eastward. This moisture will interact with a weak front
that is forecast to slide south to around I-80 by 00Z Friday
resulting in a mostly cloudy Thanksgiving across the region. Some
light rain may make it as far south as the Sacramento region by
mid to late afternoon. Only light amounts of QPF are expected with
less than a quarter inch in the mountains and only a few
hundredths of an inch in the Sacramento Valley.

Precipitation is expected to retreat northward tonight and Friday
as ridging reasserts itself across NorCal ahead of a stronger wave
developing over the eastern Pacific. Most of the region will see
dry weather for Friday into Saturday with mild temperatures.

A stronger frontal system is forecast to spread precipitation
southward across interior NorCal Saturday night and Sunday along
with stronger southerly winds. Snow levels will remain high ahead
of the front limiting potential winter weather impacts to travel
at the end of the holiday weekend.

&&
.EXTENDED DISCUSSION (Monday THROUGH Thursday)

The 12z GFS is a bit quicker than the ECMWF with the easterly
progression of the Sunday-Monday storm system, with precipitation
ending by Monday evening. The ECMWF holds onto precipitation
across the region into Monday night. By Tuesday into Wednesday,
confidence is high that a strong ridge of high pressure will bring
dry weather to Northern California. Depending on how much
northerly wind develop behind the frontal system, we could also
see fog development again in the valleys. Dry weather is likely to
continue through the rest of the extended period.

Dang

&&
&&

.AVIATION...

Extensive mid and high cloudiness bringing less foggy conditions
than last night. Patchy IFR/LIFR fog still possible in the Central
Valley, mainly from KMYV southward, into the morning. A weak
frontal system will bring light rain showers and local MVFR
conditions mainly north of Interstate 80 today. Light winds
continue.

Dang

&&

&&

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

$$


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