Area Forecast Discussion
Issued by NWS Sacramento, CA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

000
FXUS66 KSTO 192200
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
300 PM PDT Mon Oct 19 2020

.SYNOPSIS...
Dry weather and breezy northerly flow will continue this week with
periods of stronger winds resulting in elevated fire weather
conditions. Cooler temperatures by the weekend with a slight
chance of showers over the mountains.

&&

.DISCUSSION...
High amplitude upper ridge remains centered over the eastern
Pacific and into NorCal today through the week. Visible satellite
shows clear skies over NorCal today with very little smoke
emanating from area wildfires. Temperatures this afternoon are
similar to this time yesterday, with some locations a few degrees
cooler. Overall, high temperatures today and Tuesday will remain
unusually hot, around 10 to 15 degrees above normal, peaking in
the upper 80s to low 90s across the Valley.

As the upper ridge axis moves slightly east and becomes more
amplified, surface gradients over NorCal are forecast to tighten
late tonight through tomorrow. Winds will increase over the
Sierra, foothills, Sacramento Valley, and associated terrain.
North to east winds with gusts up to 20 to 30 mph are possible,
locally stronger over the wind prone gaps and canyons. Strongest
winds for the mountains and foothills will be tonight through late
tomorrow morning. These gusts plus extremely low RH and dry fuels
will create elevated to locally critical fire weather conditions.
The Fire Weather Watch has been upgraded to a Red Flag Warning.

A series of short-wave troughs moving through the PacNW beginning
Wednesday will weaken high pressure over NorCal during the second
half of the week. Temperatures will begin to trend down slightly
on Wednesday, with a bigger drop forecast on Thursday as highs
fall to only slightly above average.

North and east pressure gradients are forecast to tighten again
late Wednesday night through Thursday, this time more
significantly than the first system. Stronger winds are forecast
during this time period, sustained north to east winds 15 to 25
mph with gusts up to 40 mph, locally higher over wind prone areas.
Breezy winds are likely to continue into Friday. This will renew
critical fire weather concerns, and a Red Flag Warning has been
issued. HEC

&&

.EXTENDED DISCUSSION (Friday THROUGH Monday)...
Ensembles continue to show a weak shortwave trough moving through
the area Friday, which bring continued breezy winds and cooling
temperatures. A stronger trough is slated to slide down through
the Great Basin region Saturday into Sunday with associated
shortwave moving through NorCal. This will initially bring a
slight chance of showers to the higher terrain Saturday, though
current model runs have backed off on this somewhat. Temperatures
will also cool a few more degrees back to near to slightly below
normal with highs in the upper 60s to low 70s across the Valley.

The main concern with this trough is the breezy winds that will
follow on Sunday into Monday as surface gradients tighten once
again. The trough will not bring much humidity relief to the area,
and daytime RH will remain quite dry Sunday into Monday. These
could bring another period of enhanced fire weather concerns for
NorCal. However, temperatures are expected to remain near normal
through this time. HEC

&&

.AVIATION...
VFR conditions continue over interior Northern
California conditions through 06z Tuesday with winds generally
below 10kts. North wind gusts 15 to 25 mph possible over the
northern Sacramento Valley after 18z.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 11 PM this evening to 8 AM PDT Wednesday
for Central Sacramento Valley in Glenn, Colusa, Yuba, Northern
Sutter, and Butte County Below 1000 Ft-Eastern Mendocino NF-
Eastern Portion of Shasta/Trinity NF-Northern Sacramento Valley
to Southern Tehama County Line Below 1000 Ft-Northern Sierra
Foothills from 1000 to 3000 Ft. Includes portions of Shasta-
Trinity and Butte Units-Northern Sierra Including Lassen NP and
Plumas and Lassen NF/S West of the Sierra Crest (West of Evans
Peak-Grizzly Peak-Beckworth Peak)-Northern Sierra Including the
Tahoe and ElDorado NF/S West of the Sierra Crest-Southeast Edge
Shasta-Trinity NF and Western Portions of Tehama-Glenn Unit-
Southern Sacramento Valley in Yolo-Sacramento Far Western
Placer, southern Sutter and Solano County Below 1000 Ft-
Stanislaus NF West of the Sierra Crest.

Fire Weather Watch from Wednesday evening through Friday
afternoon for Carquinez Strait and Delta-Central Sacramento
Valley in Glenn, Colusa, Yuba, Northern Sutter, and Butte County
Below 1000 Ft-Eastern Mendocino NF-Eastern Portion of
Shasta/Trinity NF-Northern Sacramento Valley to Southern Tehama
County Line Below 1000 Ft-Northern San Joaquin Valley in San
Joaquin and Stanislaus Counties Below 1000 ft-Northern Sierra
Foothills from 1000 to 3000 Ft. Includes portions of Shasta-
Trinity and Butte Units-Northern Sierra Including Lassen NP and
Plumas and Lassen NF/S West of the Sierra Crest (West of Evans
Peak-Grizzly Peak-Beckworth Peak)-Northern Sierra Including the
Tahoe and ElDorado NF/S West of the Sierra Crest-Southeast Edge
Shasta-Trinity NF and Western Portions of Tehama-Glenn Unit-
Southern Sacramento Valley in Yolo-Sacramento Far Western
Placer, southern Sutter and Solano County Below 1000 Ft-
Stanislaus NF West of the Sierra Crest.

&&

$$



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.