Lathrop, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

988
FXUS66 KSTO 211206
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
406 AM PST Thu Nov 21 2024

.SYNOPSIS...
A strong atmospheric river brings periods of moderate to heavy
rain and mountain snow, isolated thunderstorms, and gusty
southerly winds to interior NorCal through the end of the week,
over the weekend and into early next week.

*Winter Storm Warning: Through 8 AM this morning for elevations above
    3500 feet along the Sierra/southern Cascades
   including Interstate 80.

*Winter Storm Watch:   From 4 PM Friday through 4 PM Tuesday for elevations
   above 5500 feet along the Sierra/southern Cascades
   including Interstate 80 and Highway 50.

*Flood Watch:          Through 4 AM Saturday for Valley/foothills
                       locations generally north Interstate 80 and
                       below 3000 feet.

*Wind Advisory:    Through 7 AM this morning for the
    Northern/Central Sacramento Valley and
   Northeast foothills.

.DISCUSSION...
As of early this morning, current RADAR illustrates widespread
precipitation spreading across interior Northern California
early on this Thursday morning. Caltrans and CHP have reported
slick roads and ponding water on roadways in the Valley, and snow
covered roads up in the mountains including Interstate 80.
The strong atmospheric river continues to bring periods of
moderate to heavy precipitation to the region today and over the
next several days, before moving onshore over the weekend and
bringing additional widespread precipitation to the area.

Some lingering snow showers will be possible through the morning
up in the Sierra Nevada, and the current Winter Storm Warning has
been extended through 8 AM, as snow is still falling and mountain
travel impacts are still being observed primarily along I-80.
Snow levels are expected to continue to rise through the day
today, starting out initially around 6000-7000 feet, and rising to
around 7000-8000 feet later this morning. This will allow for
rainfall to be the primary precipitation across interior NorCal
today into Friday. Snow levels then start to come down Friday
evening and over the weekend, lowering to around 4000-6000 feet
Saturday and Sunday (lowest in Shasta County). Periods of moderate
to heavy snow are currently expected to continue over the weekend
and into next week, and a Winter Storm Watch has been issued from
4 PM Friday through 4 PM Tuesday for elevations in the Sierra and
southern Cascades above 5500 feet.

Periods of moderate to heavy rain will continue over the next
several days. Rain amounts of 1-5 inches in the Valley with 3-12
inches in the foothills are in the forecast through Saturday
morning, with an additional amounts of 0.25-2 inches from Saturday
into Sunday as the system moves inland. The Flood Watch remains
in effect through 4 AM PST Saturday. Slick roads, ponding of water
on roadways, and sharp rises on rivers, creeks and streams
continues to be possible.

Periods of gusty southerly winds will also continue over the next
several days. Winds are still gusting to around 25 to 40 mph in
portions of the northern and central Sacramento Valley and
adjacent foothills, and the Wind Advisory is in effect through
7 AM PST this morning. Another round of gusty southerly winds
will develop later tonight into Friday. Isolated thunderstorms
will be possible Friday afternoon into Saturday, and the National
Blend of Models (NBM) suggests a 10-20% probability of
thunderstorm development over this timeframe. Isolated
thunderstorms may produce small hail, heavy rain, lightning, and
gusty winds.

.EXTENDED DISCUSSION (Monday THROUGH Thursday)...
By the start of the work week, rain and mountain showers will
continue to impact interior Northern California through Tuesday as
the aforementioned trough pushes inland. Snow levels are forecast
to be between 5000-6000 feet Monday through Tuesday, with
additional forecast snow accumulations of 6 to 12 inches and up to
2 feet along the highest peaks of the Sierra. Probabilities of
exceeding 12 inches are between 50% and 70%. Across the Valley,
there is a 40 to 60% chance of rainfall accumulations of 1.00 inch
or more through Wednesday morning. Lower elevation precipitation
is expected to persist as well, with totals of 0.5 to 1.5 inches
possible across the Valley and foothills and 1 to 3 inches
possible across the mountains through Tuesday.

Heading into the midweek timeframe, there is some uncertainty
whether this period of active weather may slowly taper off or
persist. Ensemble solutions diverge slightly. The favored solution
shows the potential for an additional few inches of mountain
snow. The National Blend of Models projects an a 40 to 50% chance
of 2.00 inches of snow or more over the Sierra, Wednesday into
Thursday with snow levels around 5000 to 6000 feet. Rainfall
amounts in the Valley and mountains during this time will be far
less compared to previous active weather periods, with a 20 to 40%
chance of 0.5 inch or more across the Valley and foothills.

Be sure to stay up to with the latest forecast at weather.gov/sto
if you have outdoor holiday plans and check current road
conditions at quickmap.dot.ca.gov before traveling!



&&

.AVIATION...
Moderate to locally heavy precipitation continues to move across
the region resulting in periods of VFR/MVFR/IFR conditions across
the Sacramento Valley and foothills with isolated areas of
IFR/LIFR in the mountains through 12Z Friday. Periods of gusty
southerly winds are also expected up to 20 to 30 kts across the
Valley and foothills through 12z Friday. Strongest winds will be
along the northeastern Sierra foothills with gusts 35 to 45 kts
through 14z Thursday. Over the Sierra, southerly winds gusting 30
to 45 kts through 12z Friday.


&&

.STO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late Friday night for Central Sacramento
Valley-Mountains Southwestern Shasta County to Western Colusa
County-Northeast Foothills/Sacramento Valley-Northern Sacramento
Valley-Shasta Lake Area / Northern Shasta County.

Wind Advisory until 7 AM PST this morning for Central Sacramento
Valley-Northeast Foothills/Sacramento Valley-Northern Sacramento
Valley.

Winter Storm Warning until 8 AM PST this morning for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.

Winter Storm Watch from Friday afternoon through Tuesday
afternoon for West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.

&&

$$