Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 310540
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
940 PM PST Fri Jan 30 2015
Dry weather expected through the middle of next week except
for some mainly light precipitation possible in far northern
portions late Sunday into Wednesday. Some breezy north to east
wind continues into Saturday with above normal temperatures.
Night and morning fog possible in the Central Valley, becoming more
widespread Sunday into early next week. Models suggest a change to a
potentially wet weather pattern towards the end of next week.
.Short Term Discussion (Today through Monday)...
Surface high building into NWrn NV will maintain moderately strong
N and NE gradients tonite and into Sat morning to keep downslope
flow a factor in adiabatic warming and mixing. Have upped mins a few
degrees tonite...mainly in the Nrn Sac Vly and along the W side of
the Sac Vly in deference to a modest Nly barrier jet. Only a strip
of fog was evident this morning...and we expect even less coverage
Sat morning due to the Nly flow. JHM
Upper ridging beginning to nose into the PacNW while surface ridging
extends into the Great Basin.
Upper ridging continues to build over NorCal tonight into Saturday
as upper low to the south digs. Low level pressure gradient
strengthens further tonight into early Saturday as it becomes more
E-W oriented over NorCal. This will favor stronger winds over the
eastern foothills/mountains and along the west side of the
Sacramento Valley into the Delta. AMS undergoes synoptic warming
tomorrow with increasing heights/thicknesses. Highs tomorrow
near record values in the Northern Sacramento Valley with
readings in the mid 70s, with upper 60s to lower 70s throughout
the remainder of the Central Valley.
Upper ridging flattens some Sunday as impulses ride over the top of
it into the PacNW. Greater area of morning valley fog possible in
the San Joaquin and possibly into the Southern Sacramento Valley and
Delta Sunday morning under lighter surface wind and increased
subsidence. Some associated overrunning cloudiness Sunday and
Monday will result in slight cooling over Interior NorCal. Models
depict potential for some light overrunning precip over mainly
Shasta county Sunday night into Monday.
.Extended Discussion (Tuesday through Friday)
A flat ridge of high pressure will remain over most of the area
through the middle of next week, bringing continued dry weather. A
few weak impulses riding over the ridge could bring periods of
precipitation to northern CA, including Shasta County and Lassen
The more significant pattern change will occur late next week, as
the ridge shifts eastward and an Atmospheric River likely takes
aim at the West Coast. As with many AR events, the plume of
moisture is generally relatively narrow, and the biggest factor of
uncertainty is where the hose is pointed. The latest series of
model runs has this pointed at Northern California Friday through
Sunday. With confidence increasing in the potential for
precipitation toward next weekend, we increased our forecast
chances of precipitation quite a bit.
Mainly VFR conditions across interior Northern California the next
24 hours, except local MVFR/IFR conditions in the Northern San
Joaquin Valley early Saturday morning.
North winds 10-20 kt along the northern and western Sacramento
Valley will continue through mid-Saturday then diminish. Over the
Sierra...northeast winds will increase to 15-25 kt tonight, with
locally higher gusts.