Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 052236
Area Forecast Discussion
National Weather Service Sacramento CA
236 PM PST Mon Dec 5 2016
Cold overnight temperatures tonight and Tuesday night. A return
to wetter weather is expected Wednesday through Saturday.
Northwesterly flow aloft continues across interior Northern
California today, with a fair amount of high cloudiness moving
across the region. Fog has been slow to burn off with poor mixing
this afternoon. As such, it wouldn`t be a surprise to fog reform
in areas south of the Sutter Buttes tonight into Tuesday morning.
Cold overnight temperatures will continue tonight and again
Tuesday night. Tuesday night currently looks like the coldest of
the bunch, with near-freezing temperatures across the Valley, and
teens and single digits over the higher terrain. A Freeze Watch
has been issued to highlight these concerns.
A weak weather system will skirt the region Tuesday, possibly
bringing light snow to the northern mountains.
A more meaningful weather system is on track for Wednesday night
into Thursday, with light precipitation expected for most of the
region. The tricky part of this forecast is that snow levels will
likely start rather low due to the initially cold airmass. Cold
air trapped trapped in valleys and some mountain locations is
notoriously difficult to scour out. At this stage, it is difficult
to gauge what the level of impact of low elevation snow will be
due to uncertainty in snow level and precipitation totals.
.EXTENDED DISCUSSION (Friday THROUGH Monday)
Unsettled pattern looks to continue thru much of the extended
period. Precipitation will continue during the day Friday as swath
of moisture continues to steam in. Current model solutions suggest
moisture plume will intrude into the Bay area and up into the
Sierra across southern portions of the forecast area (perhaps Hwy
50 corridor and south). This would keep snow level near 7000 feet
over the Sierra during the day. Regardless, some decent
accumulations possible which may serve to impact travel heading
over the passes. NW portions may see a bit of a break in
precipitation during the period on back side of wave. Model
solutions diverge from Friday night with the ECMWF showing an
additional wave of precipitation, perhaps substantial, during the
day Saturday, while GFS remains mostly dry outside a few Sierra
showers. Given such a large difference, have hedged toward a blend
of solutions with precipitation over most of the area, until
solutions are better aligned. Snow levels may drop lower with this
wave should it occur which would further impact weekend mountain
travel. Certainly something to keep an eye on going forward.
Next wave moves across the area on Sunday. GFS wetter with this
wave vs drier ECMWF. Regardless, looks like best chance for
widespread precip across the mountains with spottier showers at
lower elevations. Snow levels around 4000 feet across northern
mountains and 5000 feet in the Sierra. Showers taper off later
Sunday into Monday, with a break in precipitation possibly. Models
hint at additional systems into middle of next week!
Areas of Valley MVFR and local IFR to LIFR in BR/FG possible
again Tuesday morning generally south of MYV. Light northerly flow
under 10 kts thru the period.
Freeze Watch from late Tuesday night through Wednesday morning
for Central Sacramento Valley-Clear Lake/Southern Lake County-
Motherlode-Northeast Foothills/Sacramento Valley-Northern
Sacramento Valley-Northern San Joaquin Valley-Southern