Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 251701
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
901 AM PST Thu Dec 25 2014
Mainly dry weather will continue for the next week, with periods
of breezy north winds and colder overnight low temperatures.
Northern California is now under broad northerly flow between an
upper trough over the Rockies and an upper high over the eastern
Pacific. A few showers are being picked up on radar along the
northern coast, but are unlikely to reach our forecast area. The
Medford-Sacramento pressure gradient is considerably weaker than
yesterday afternoon, but remains strong enough to maintain modest
northerly breezes across the area. Temperatures are considerably
cooler than yesterday, but north winds have kept conditions mixed
enough to prevent temps from dropping even further.
Not much change is expected the next few days as we transition to
a drier pattern. Periods of north winds will continue,
particularly along the western Sacramento Valley. Expect highs in
the mid 50s across the Valley, with 30s and 40s over the
mountains. These forecast highs are much closer to normal than
we`ve recently seen.
Low temperatures will also be much cooler than recently seen. This
may be the trickiest aspect of the forecast the next several days,
with the lows highly dependent on if winds drop off overnight.
We`ll take a closer look at this and see if frost needs to be
added to the short term forecast.
.Extended Discussion (Monday through Thursday)
The most significant weather events in the extended will be
breezy to strong northerly to northeasterly winds Monday and
Tuesday followed by cold overnight temperatures.
Models are still agreement that a very high amplitude ridge is
just inside 140W on Monday with a broad upper low over the
northern Great Basin (southern Idaho). A shortwave and associated
cold front slides down the eastern side of the ridge, which may
brush the higher Sierra with a minimal chance of light snow
showers due to very little moisture associated with this system.
What this dry cold front doesn`t bring in moisture, it brings in
post-frontal cold air and breezy to strong offshore surface winds
Monday and Tuesday. By Wednesday/Thursday, the ridge axis moves
closer to the coast which will begin to weaken winds. As a
result, much colder temperatures will likely occur. The best
chance for frost and freezing valley temperatures will likely be
Wednesday/Thursday when winds subside, especially on the less
windy eastern side of the valley. JClapp
VFR conditions with breezy north surface winds today in Central
Valley after 17z with sun mixing boundary layer (sfc-030). Gusts
20 to 30 kts by afternoon and toward sunset. Sustained winds 20
to 30 kts at 2-3K MSL continue today. JClapp