000
FXUS66 KSTO 221000
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
300 AM PDT Tue Oct 22 2019

.SYNOPSIS...
Breezy conditions at times, especially Wednesday into Thursday
when elevated fire weather concerns are expected. Dry conditions
with above average temperatures forecast through the remainder of
the week.

&&

.DISCUSSION...
Broad ridge over the eastern Pacific and NorCal continues to
provide clear skies. Current temperatures range from the upper 20s
in the mountain valleys to the mid 60s across milder portions of
the Central Valley and foothill thermal belts. North to northeast
pressure gradients are a bit tighter compared to early Monday
resulting in gusts in the 15-25 mph range across the northern
Sacramento Valley and local gusts of 20-40 mph in the foothills of
Butte County.

Warm and dry weather will continue this week with highs forecast
to be around 5 to 15 degrees above average. Overnight lows will
be mild across windier portions of the valley and in the foothills
thermal belts, but will be close to normal elsewhere.

The main concern this week is enhanced fire weather conditions,
especially for Wednesday and Thursday, as the short-wave presently
moving through southern BC digs into the central US. As this
happens, the upstream ridge is forecast to amplify along 130W
providing a little better upper level support to the tightening
north/northeast surface gradients.

Lighter winds forecast to return later Thursday and continue
Friday as the ridge moves overhead.

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...
Models in good agreement in dropping an upper trough out of
western Canada and into the northern Great Basin on Saturday.
Impacts on Saturday will be minimal. There should be a little
cooling but daytime highs Saturday are still likely to come in
several degrees above normal. Models continue diverged going into
early next week with a fairly significant difference in impacts
depending on solution. ECMWF continues to dig the upper trough
southward into the central Great Basin Sunday while the GFS tracks
the trough much farther east into the central U.S. during this
same timeframe. ECMWF solution would bring another round of strong
northerly winds to most of the CWA while the GFS solution would
leave Norcal under light gradients and lighter north winds. Either
way, daytime temperatures cool behind the trough with daytime
highs dropping to near normal on Sunday. Leaning towards a middle
of the road approach to the winds Sunday and have gone with
relatively light north winds. Continued northerly flow will bring
a little more cooling on Monday with daytime highs dropping to
slightly below normal. Upper ridge slides over the west coast next
Tuesday bringing a slight warm up.

&&

.AVIATION...
VFR conditions the next 24 hours at TAF sites. Generally
northerly sustained winds 5 to 15 knots.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from late tonight through Thursday 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-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 Sacramento Valley in Yolo-
Sacramento Far Western Placer, southern Sutter and Solano County
Below 1000 Ft-Stanislaus NF West of the Sierra Crest.

&&

$$