Wind Advisory 23, NWS Sacramento, CA

Area Forecast Discussion
National Weather Service Sacramento CA
349 PM PDT Fri Oct 25 2019

.SYNOPSIS...
Dry weather with above average temperatures through Saturday. A
strong wind event Saturday into early Monday will result in
extreme fire weather danger. Enhanced fire weather concerns
possible by the middle of next week.

&&

.DISCUSSION...
Dry and warm weather continues as EPAC ridging remains overhead.
Slight cooling begins Saturday as the next upstream system
approaches leading to minor synoptic cooling. Breezy northerly
winds are expected to redevelop through the Sacramento Valley
during the day on Saturday, bringing increasing fire weather
concerns.

Main concern is the potential for extreme fire weather danger
Saturday night into early Monday. Deterministic and ensemble
models indicate a deepening trough late in the weekend. The
pattern would result in another north/northeast wind event
beginning Saturday night and continuing into early Monday.

Strong, possibly damaging, winds are likely Saturday night into
Sunday as surface pressure gradients tighten, upper level support
aligns with the terrain of the Central Valley, and subsidence
increases in the wake of the trough. The MFR-SAC gradient is
forecast to peak around 16 mbs while the RNO-SAC gradient is
forecast to peak at 12-14 mbs.

Peak wind gusts across the lower elevations will be in the 45-55
mph range while the foothills and mountains will see gusts of
55-65 mph or higher. The strongest wind gusts will be observed
along the western side of the Sacramento Valley, the Delta, and higher
elevations. Delta areas will be particularly susceptible to
damaging easterly winds in this situation. Therefore, a High Wind
Warning has been issued for portions of the Sacramento Valley and
the surrounding foothills and mountains beginning Saturday
evening into Sunday evening. Downed trees, power outages, and
difficult driving conditions are possible. In addition, a Wind
Advisory is in effect for the northern San Joaquin Valley, where
winds are not expected to reach warning criteria.

The combination of strong winds and extremely dry weather will
bring extreme fire weather conditions to much of interior northern
California. Therefore, a Red Flag Warning has been issued for the
northern/central Sacramento Valley beginning Saturday morning,
and expanding into most areas Saturday night. The extreme fire
weather will continue into early Monday morning. Please practice
fire safety and be ready to evacuate if a fire starts near you.

Temperatures will cool significantly early next week, with Valley
highs in the low to mid 70s.

&&

.EXTENDED DISCUSSION (Tuesday THROUGH Friday)...

The synoptic pattern remains on repeat as a broad upper ridge
remains fixed over the Eastern Pacific. To its east, longwave
troughing continues to spin up embedded disturbances which may
influence the region. While the weekend system will have already
become absorbed into the mentioned central U.S. trough, another
feature remains worth monitoring. A shortwave currently over the
Arctic Ocean is forecast to dive down through central Canada
before emerging over the middle of the country by early Tuesday.
Global ensembles continue to diverge with the track of this system
as the ECMWF remains well west of the GEFS/NAEFS means. Height
gradients are broad, but impressive which suggests there is a
decent potential for additional dry, northerly flow on Tuesday
into at least Wednesday morning. Until the models come into better
agreement, it remains difficult to pinpoint more precise impacts,
particularly regarding fire weather concerns. In the wake, there
is some uncertainty but it appears the offshore ridge will
gradually edge eastward aligning with Pacific coast by next Friday
(Nov 1). This will ensure continued dry conditions across the
state.

High temperatures next week should stay near average for this time
of year with Valley readings in the low to mid 70s while being
closer to 80 near Redding. Optimal radiational cooling will bring
overnight lows into the 40s while foothills locations stay in the
upper 40s to near 50 across the typical thermal belts.  ~BRO

&&

.AVIATION...

VFR conditions with mostly clear skies are expected over the next
24 hours. TAF sites should see light north winds through this
afternoon, generally around 5 knots, becoming light and variable
by this evening. By 12Z Saturday, northerly winds pick up at KRDD
and KRBL, likely in the 10 to 13 knot range.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 11 PM Saturday to 11 PM PDT Sunday for
Carquinez Strait and Delta-Central Sacramento Valley-Clear
Lake/Southern Lake County-Motherlode-Mountains Southwestern
Shasta County to Northern Lake County-Northeast
Foothills/Sacramento Valley-Northern Sacramento Valley-Southern
Sacramento Valley-West Slope Northern Sierra Nevada-Western
Plumas County/Lassen Park.

Red Flag Warning from 11 AM Saturday to 11 AM PDT Monday for
Burney Basin and Northeast Plateau in Shasta County Including
Northwest Lassen NF north of Lassen NP-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-Lake County Portion of Lake-
Napa-Sonoma Unit-Northern Motherlode From 1000 to 3000 Ft.
Includes portions of Nevada-Yuba-Placer-Amador and ElDorado
Units-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 Motherlode
From 1000 to 3000 Ft. Includes portions of Calaveras-Tuolumne
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.

Wind Advisory from 11 PM Saturday to 11 PM PDT Sunday for
Northern San Joaquin Valley-Shasta Lake Area / Northern Shasta
County.

&&