Area Forecast Discussion
Issued by NWS Sacramento, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49
000
FXUS66 KSTO 222250
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
250 PM PST Mon Jan 22 2018

.Synopsis...
Fair tonight into Tuesday with some patchy morning valley fog
possible. Stronger Pacific storm impacts the area Wednesday into
Friday with periods of moderate to heavy rain and mountain snow,
and gusty wind. Drier weather Friday into the weekend.

&&

.Discussion...
Shower activity winding down this afternoon as subsidence is
increasing over the forecast area. Bufkit moisture profiles
showing abundant lower level moisture tonight with ceilings
lowering to the surface in portions of the Delta, Southern
Sacramento and Northern San Joaquin Valleys overnight into
Tuesday morning. Upper ridging brings drier weather Tuesday as
high temperatures trend up to near or slightly above normal.

Stronger Pacific frontal system is forecast to move through
Interior NorCal Wednesday. Models similar with timing, pushing
frontal precip into Western Shasta and the Coastal Range by 18z
Wed, then across all of Interior NorCal Wednesday into Wednesday
night. Breezy to windy conditions develop ahead of the front. At
this time it looks like speeds will remain below advisory criteria
in the Central Valley. However strong winds possible in the
mountains, especially over higher terrain where gusts 40 to 60 mph
are possible. Snow levels initially look to be around 4000 to
6000 feet Wednesday, but lower to 2000 to 3500 feet behind the
front Wednesday night and Thursday. Heavy snow expected in the
mountains of Western Plumas and Northern Sierra Nevada Wednesday
night into Thursday and have a Winter Storm Watch in effect.
Several feet of snow is possible over the highest elevations. As
snow levels lower significantly behind the front Wednesday night
and Thursday, accumulating snow in the Coastal and Shasta
mountains may warrant additional winter weather products. Could
also see some light accumulations in the upper elevations of the
NE foothills and Motherlode Thursday.

Unsettled weather continues Thursday as post frontal upper
troughing moves through. Models showing limited CAPE attm
Thursday, but trending up. With steepening lapse rates Thursday
afternoon as 5H temps cool into the lower -30s Deg C, will need
to continue to monitor for potential thunderstorm activity. Storm
total liquid QPF for this system ranges from about a third to one
inch and a half inches in the Central Valley (highest in the
Northern Sacramento Valley), with 1 to 4 inches for the foothills
and mountains.

PCH

&&

.EXTENDED DISCUSSION (Friday THROUGH Monday)
Ridge of high pressure will begin to build over California late
this week, and continuing into early next week. This will likely
push the storm track northward into the Pacific Northwest. Periods
of light, overrunning precipitation will be possible across far
northern CA, but most of the region will likely remain dry for
this time period. A fair amount of mid to high cloudiness should
stream over the region, which makes the Valley fog forecast
challenging this far out.

Dang

&&

.AVIATION...
Weather system has shifted eastward, and precipitation is slowly
tapering off this afternoon. Abundant residual moisture is
bringing widespread MVFR/IFR conditions across the region.
Conditions will likely deteriorate to IFR/LIFR in Valley locations
tonight into Tuesday morning as fog forms.

Dang

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Wednesday afternoon through Friday
morning for West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.

&&

$$


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.