NATIONAL WEATHER SERVICE FORECAST DISCUSSION
Area Forecast Discussion
Issued by The National Weather Service
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000
FXUS66 KSTO 131700
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
900 AM PST Wed Feb 13 2019

.SYNOPSIS...
A strong storm event will bring widespread precipitation with
moderate to heavy rain and mountain snow. Local flooding with
ponding on roads and rises on streams and river possible through
Thursday. Periods of wet weather continue into the weekend.

&&
.Update Discussion...
Moderate to heavy rain is impacting the area this morning, with
Caltrans reporting multiple areas in the Valley with local road
flooding/ponding. In addition to the rainfall, melting snow in the
foothills will add to runoff. An areal Flood Warning has been
issued for much of the Valley and foothills through 8 pm tonight,
when there should be some decrease in intensity in the rainfall.
Motorists should use caution when driving during this storm event
and should avoid flooded roads:
"Turn around, don`t drown!". EK

.Previous DISCUSSION...
Moderate to heavy precipitation with the initial wave of the storm
has spread across the northern half of the forecast area overnight
while lighter precipitation has been falling to the south. Gusty
southerly winds persist especially from about I-80 southward where
gusts of 35-45 mph have been rather common overnight in the
foothills to the south and east of Sacramento. Lighter north winds
have been present across the northern half of the Sacramento
Valley as surface low pressure approaches from the southwest.

Cold air remains entrenched across the far north end of the
Sacramento Valley and northern mountains, where moderate to heavy
snowfall has been occurring since Tuesday evening, while warmer
air has been rapidly moving in across the remainder of the region
with snow level radars indicating snow levels above 8-9k feet.
Snow has just switched over to rain at KBLU, but the transition
will be slower across Shasta County where warming of the sounding
from the top down may lift snow levels a bit by later this morning
and this afternoon.

The remaining cold air should be mixed out of the northern
mountains later tonight and early Thursday as next surface low
races northward off the coast up into western Oregon by midday
Thursday. This will also bring another upswing in precipitation
and gusty southerly winds as gradients tighten to around 15 mbs
from SAC to MFR bringing an elevated risk for power outages and
tree damage. This will also be the period where there will
increased potential for any flooding issues as runoff from the
ongoing precipitation is enhanced by low-elevation snow melt.

Snow levels expected to come back down Thursday afternoon and
night as the next cold upper low drops down to off the coast of
Oregon and displaces the milder airmass to the east. At the same
time, snowfall will increase over the northern Sierra Thursday
night as lapse rates steepen and upslope component to the flow
increases. A few thunderstorms will be possible in the Central
Valley.

Wet and cooler pattern will continue into the weekend as several
disturbances drop down from the northwest bringing showers and
adding to the snowpack in the mountains.

&&
.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)


An upper trough will be moving across the west coast Sunday into
Monday bringing continued precipitation chances to NorCal. Light
valley rain remains possible on Sunday, although the better chances
for precipitation look to be over the mountain and foothill regions.
Additional snow accumulations of around six inches may be possible
Sunday and Sunday night with snow levels as low as 1500 feet Sunday
afternoon, falling to around 1000 feet Sunday night. Minor travel
impacts are possible this day. Dry weather returns Monday night and
Tuesday, with another system possible mid next week.  Cold low
temperatures will be seen early next week.

&&

.AVIATION...


Widespread precipitation has spread over NorCal with deteriorating
conditions seen at sites. Primarily MVFR/IFR ceilings and
visibilities are expected through the forecast period, although
localized LIFR will be possible with any heavy precipitation.
South winds pick up in the southern Sacramento Valley this morning
with gusts up to 35 kts possible.


&&

.STO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Thursday afternoon 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-Shasta Lake Area / Northern
Shasta County-Southern Sacramento Valley-West Slope Northern
Sierra Nevada-Western Plumas County/Lassen Park.

Winter Storm Warning until 4 PM PST Friday for Burney Basin /
Eastern Shasta County-Mountains Southwestern Shasta County to
Northern Lake County-Northeast Foothills/Sacramento Valley-
Northern Sacramento Valley-Shasta Lake Area / Northern Shasta
County-West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.

Wind Advisory from 6 AM to 6 PM PST Thursday 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.

&&

$$
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