Forecast discussion from National Weather Service/Sacramento
We are going to see a major weather pattern change starting later
Monday as deep troughing builds over the West. This will bring
multiple rounds of rain and snow through the week and through the
weekend. Dense fog has developed over the Valley and we should see
that slowly lift into a stratus layer throughout the morning into
early afternoon. This will once again hold temperatures down in
lower elevations with mild temperatures in the foothills.
Light showers begin to push in during the afternoon into the
evening mainly over the northern mountains and north Valley as
warm air advection start to develop over the area. Low level winds
will amplify later Monday evening into Monday night as the trough
digs strengthening the warm front and bring widespread moderate
to heavy rain over NorCal. This system will tap into deep Pacific
moisture with the Integrated Water Vapor (IVT) pushing upwards of
1000 kg/ms and PWATs 1.0-2.0". The cold front will then work south
through NorCal Monday morning into the afternoon likely stalling
out for a time over the northern San Joaquin Valley. Moderate to
heavy rain can also be expected along and ahead of the front.
Activity will become more showery during for a time in the
afternoon except over the mountains where upslope flow will keep
widespread rain/snow going. Showers will become more widespread
again during the evening and early overnight as a short wave
trough axis pushes through. Mainly dry conditions will set in
Wednesday morning into the afternoon as northwest flow develops.
Localized flooding will be possible with this rain as streams and
creeks rise and roadway flooding of poorly drained areas will
become an issue as well.
Some weak instability builds in right behind the cold front and
that may bring a thunderstorm or two during late morning into the
early overnight mainly from around Stockton north. CAPE looks
limited and the thunderstorm threat should remain isolated.
The amplifying low level jet is going to bring strong winds to the
area Monday night into Tuesday. 850 mb winds increase to 50-70
knots ahead of the cold front with 700 mb winds 60-85 knots.
Winds gusts from Sacramento north will be 40-55 mph with wind
gusts possibly up to 65 mph east of I-5 from north of Chico to
Redding. Gusts 35-50 mph are expected over the northern San
Joaquin. Gusts 50-85 mph are expected over the Mountains .
With a good stream of deep Pacific moisture we will see high snow
levels with the onset of the precip with them 7500-8500 feet. Cold
air will begin to build in Tuesday afternoon and we will see snow
levels start to fall falling to 4500-5500 feet Wednesday. 6-24"
of snow is expected above 5500 feet with up to 35 inches over the
higher peaks. Some light accumulation will be possible down to
4500 feet Wednesday morning. QPF totals through Wednesday
afternoon are looking to be 1.50-3" in the Valley, 2.50-4.50" in
the foothills, and 4-6" over the mountains. We are expecting a
period of moderate to heavy rain but convective rain is looking
limited, this should keep rain rates below burn scar thresholds.
Dry weather will not last long with rain and snow returning
Wednesday night into Thursday as a short wave pushes to our north.
This will bring another round of widespread precipitation. Snow
levels Wednesday night will be 3500-4500 feet but they will be
rising Thursday reaching 5500-6500 feet. Moisture will remain
elevated over the region and moderate rain and heavy snow can be
expected at times.
EXTENDED DISCUSSION (Friday THROUGH Monday)...
The storm train is going to keep on rolling through the extended
period. We will see another round of widespread precip Thursday
night into Friday as another short wave trough pushes to our
north. Moderate rain and heavy snow can be expected at times again
with this wave. Another short wave will dig deeper over the
Pacific Friday night into Saturday. This one will be able to pull
in higher moisture levels and we will likely see a period of
moderate to locally heavy rain along with heavy snow. This trough
is looking to favor southern areas with the heaviest precip
expected from about I-80 south. Some of the timing and location
may change with these short wave toughs but unsettle wet weather
will continue. It does look like we will see a break from rain and
snow late Saturday night and throughout the day Sunday as a
stronger short wave ridge builds in. Once again the break doesn't
look to last long as additional short wave trough move in early
next week bringing the return of rain and snow.
-CJM