Placerville, CA (near 1,850 ft. elevation - 95667)

Wx Discussion - Wx Hazards - Wx Special Statements

Expanded Placerville Weather Forecast

Weather Forecast Discussion

000
FXUS66 KSTO 212147
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
247 PM PDT Wed Oct 21 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 potentially
another strong north to east wind event Sunday into Monday.

&&

.DISCUSSION...
Upper level heights are dropping today as a shortwave trough moves
through the PacNW, breaking down the high pressure over northern
California. Visible satellite is showing mostly clear skies with a
few upper level clouds across the area. A cooling trend begins
today as a dry surface front moves through the area. Surface
pressure gradients have tightened once again this morning through
early this afternoon with the current MFR-SAC gradient around 9 mb.
This is creating locally gusty winds in the northern Sacramento
Valley with gusts up to 20 to 30 mph. Conditions remain extremely
dry with low RH in the teens and 20s and near record dry fuels.

As the upper shortwave continues to dig southeast tonight through
tomorrow, surface gradients are expected to continue to tighten.
Winds will begin to increase late tonight through tomorrow with
strong north winds in the Sacramento Valley and downslope winds in
the foothills. Strongest winds will be around midnight tonight
through tomorrow afternoon with gusts up to 30 to 45 mph. Gusty
winds will continue through tomorrow night with gusts up to 20 to
30 mph. Winds will be locally higher in wind prone gaps, canyons,
and ridges. A Wind Advisory has been issued for tomorrow morning
for the strong Valley winds. Dry conditions will continue through
the end of the week as daytime minimum RH values remain in the
single digits to low 20s with locally poor overnight recoveries.
These dry conditions plus the strong winds will create critical
fire weather conditions, and a Red Flag Warning is in effect
through Friday afternoon.

Temperatures will continue to cool through the week with daytime
temperatures returning to near normal for the weekend. Another
shortwave is forecast to slide through the Intermountain West on
Saturday, digging into the Great Basin area beginning Saturday
night. Depending on the location of the shortwave, there could be
a chance of light mountain showers, though model confidence
remains low and continues to back off on this. HEC

&&

.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)...
There are no significant changes in the extended forecast. A cold
upper level trough will be digging into the Great Basin for the
start of the extended period. This will bring active weather to
NorCal mainly in the form of strong winds across the Sacramento
Valley Sunday and then over the Sierra for Sunday night into
Monday. Currently looking like a 10+ mb MFR to SAC gradient by mid
Sunday afternoon and a SAC to RNO gradient of 11+ mb Sunday
night. This should result in strong north Valley winds and strong
downslope winds in the foothills. We will also see a push of cold
air with this trough and overnight lows Sunday night will be quite
chilly falling into the teens over the Sierra and into the 40s in
the Valley. The cold air in place over the Sierra and over NV
will likely enhance some of the gusty downslope winds Sunday
night. As we head into the Monday the trough will be digging into
the Desert SW. This will leave an increased gradient over NorCal
with breezy winds continuing. At this time, this wind event looks
to be stronger than the current wind event. Very dry daytime
humidity and poor to moderate overnight recoveries are expected
along with the winds. This conditions will lead to critical fire
weather concerns during this period.

Wind will be the main impact of the trough but a few light
rain/snow showers will be possible in the high Sierra I-80 south
Sunday. Forcing looks weak and there will be a lack of moisture
and therefore little to no rain or snow accumulation is expected.

Quieter weather settles in for the rest of the period as upper
level ridging begins to build in. High temperatures will remain
near to just below normal along with chilly overnight lows.
Daytime humidity will remain very dry with moderate overnight
recoveries.

-CJM/HEC

&&

.AVIATION...
VFR condition are expected the next 24 hours. North winds
increase over the northern Sacramento Valley this afternoon
becoming 10 to 15 knots with gusts to 25 knots. Winds remain under
10 knots for the remainder of the area. Tomorrow, north and east
winds increase for most of the area. Gusts up to 40 mph will be
possible for the Sacramento Valley while the northern San Joaquin
remains lower with gusts between 15 and 25 mph.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 5 PM PDT Friday 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.

Wind Advisory from 5 AM to 8 PM PDT Thursday for Central
Sacramento Valley-Mountains Southwestern Shasta County to
Western Colusa County-Northern Sacramento Valley.

&&

$$

Hazardous Weather Outlook

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