River Flood Warning 16, NWS Sacramento, CA

Area Forecast Discussion
National Weather Service Sacramento CA
215 PM PST Tue Feb 26 2019

.SYNOPSIS...
Rain and mountain snow, heavy at times, will continue into
Thursday with increased flooding potential. Hazardous mountain
travel persists into Thursday. Dry Friday, then more wet weather
for the weekend.

&&

.DISCUSSION...
Baroclinic zone stretched across NorCal with embedded high PW
plume (PWS > 1.25 inches in core). Radar showing heaviest precip
attm directed across the Delta and Southern Sacramento Valley, and
into the Motherlode and Northern Sierra Nevada. Mesoscale models
showing precip increasing this evening as cold front currently
near 128 W approaches. Model QPF indicating bulk of precip
overnight will be from about I-80 north. With urban and small
stream flooding already occurring, the addition of another 1 to 4
inches or rain in the Sacramento Valley, and 2 to 6 inches the
foothills and mountains over the next 24 to 36 hours will further
increase flooding potential. As a result, an areal flood warning
has been issued. Heavy snow continues in the mountains of Western
Plumas and the Northern Sierra Nevada overnight with snow levels
remaining around 5000 feet. Strong wind has been occurring in the
Northern Sacramento Valley today with sustained wind up to 35 mph
and local gusts approaching 50 mph. Forecast pressure gradients
suggest strongest wind tonight will be ahead of and along the
frontal boundary as it moves through.

Precip turns showery Wednesday morning in the post frontal AMS.
Best shower probabilities tomorrow look to be over the foothills
and mountains as snow levels trend up to around 6000 feet.
Instability values look limited so held off adding a mention of
thunderstorms in the Central Valley. Wind expected to drop below
advisory criteria Wednesday morning but remain breezy into
Wednesday evening.

Cyclonic onshore flow will keep lingering showers into Thursday,
mainly over the eastern portions of the Central Valley, extending
into Motherlode and Sierra. Snow levels lower Thursday afternoon
to around 4000 feet.

Drier weather forecast Friday into Friday night as short wave
ridging moves through, then another Pacific storm tracks inland
over the weekend.

PCH

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)
The wet pattern continues through the extended period as multiple
weather systems are expected to impact NorCal. The next system
moves in overnight Friday, bringing Valley rain and mountain snow
through Sunday. Although model consistency is still pretty low on
specifics at this point, this is storm does not look to be nearly
as wet as the current weather system. Liquid precipitation amounts
of a third of an inch up to an inch are possible in the Valley
with one to two inches possible in the foothills and mountains.
Current model runs are warmer with this system, especially over
the Sierra. Sierra snow levels now 5500 to 6500 feet. The northern
mountain levels are still a bit lower at 3000 to 4000 feet early
Saturday, rising to 4500 to 5500 feet by Saturday evening.

Light mountain showers could linger through Monday,
otherwise dry conditions are expected early next week. Another
weather system is expected to move in by midweek. Currently models
are indicating this system could bring another round of
significant precipitation, but confidence is very low this far
out. Stay tuned to forecast updates for both of these weather
systems as we hone in on the details. HEC

&&

.AVIATION...
MVFR conditions, locally IFR, expected at the TAF sites next 24
hours with IFR/LIFR over the mountains. Southerly winds 15-25 kts
gusting to 30-45 kts expected at TAF sites; gusts 45-60 kts
possible over higher terrain.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 6 AM PST Thursday for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.

Wind Advisory until noon PST Wednesday 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-Northern San Joaquin Valley-Southern Sacramento Valley.

&&