Area Forecast Discussion
Issued by NWS Sacramento, CA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 50

FXUS66 KSTO 242331

Area Forecast Discussion
National Weather Service Sacramento CA
331 PM PST TUE NOV 24 2015

A cold Pacific storm will continue to bring additional snow in
the mountains extending down into the upper foothills into
early Wednesday. Isolated Valley/foothill thunderstorms this
afternoon and overnight. Mainly dry and cold weather expected
Thanksgiving through the rest of the week with lingering flurries
over the Sierra crest.


A cold system from the Gulf of Alaska has brought heavy snow to
the mountains. Major traffic delays and numerous
accidents have been caused from heavy snow in the southern
Cascades and northern Sierra. The cold front which has brought the
heaviest precipitation is pushing through the northern Sierra and
will exit eastward by early evening.

Travel in the mountains is strongly discouraged through this
evening. Snow levels will continue to lower overnight into early
Wednesday, with snow showers continuing over the mountains and
foothills. While several inches of additional accumulation is
possible, overall snow amounts/intensity from these showers is
decreasing. The Winter Storm Warning and Winter Weather Advisories
will end for the southern Cascades and northern Coastal mountains
(the northern mountains). Will continue the Winter Storm Warning
over the northern Sierra and Motherlode foothills into Wednesday
morning, as snow showers with lowering snow levels may still
disrupt travel. Light snow showers could continue later Wednesday
and Thursday over the Sierra crest with little or no accumulation.

Behind the main front, there was an isolated thunderstorm in
Tehama and Butte counties this afternoon east of I5 which brought
small hail to the Chico area. Dry northwest flow is quickly
stabilizing the atmosphere so much of the thunderstorm activity is
probably over for the Valley. There could be a few showers and
isolated thunderstorms over the Delta area late this evening,
though, as another disturbance passes along the coastal area. Some
rain showers are possible in the Valley Wednesday, though rainfall
amounts should be mainly light.

The next concern is the cold airmass this low has brought into the
region. Near to sub freezing low temperatures are possible early
Thanksgiving for the northern Sacramento Valley, so will be
issuing a Freeze Watch. If winds go calm with clearing winds,
temperatures could be quite cold, reaching the upper 20s in some
locations. Steps should be taken to protect sensitive plants and
pets should be given proper shelter. Participants in outdoor
events such as Thanksgiving day races should dress for cold

Cool and unsettled weather continues for the rest of the week as
the low pressure system lingers over the area. EK


Models continue the development of a Rex Block along the W Coast
late in the week...with some retrogression over the weekend as
an offshore secondary low gradually rotates towards the underside
(southern portion) of the block. A cold and showery pattern will
prevail over Norcal into Sat with the potential for freezing/near
freezing temperatures continuing in the Valley and very cold
temperatures in the mountains and mountain valleys dropping into
the teens and single digits. A limiting factor for the cold morning
temperatures will be mixing winds and cloud cover.

Drier wx is expected Sun/Mon as the Rex (low) is nudged Ewd by
the energy rotating around the base of the low and as this energy
lifts NEwd. Model differences later in the period (Mon/Tue) add
some uncertainty to the forecast with the GFS a little more
progressive in spreading short wave energy inland and the ECMWF
keeping it offshore. We continued the previous forecast blend of a
wetter/more progressive solution but would not be surprised to see
the amplified ridge (Omega block) pattern reform along the coast
keeping the region dry. In any event...Sun and Mon should be
mainly dry days with moderating temps.  JHM



In Central Valley and adjacent lower foothills, widespread
MVFR/IFR developing around 13z with areas of southerly sfc wind
gusts to 25 kts. Widespread MVFR/IFR with local LIFR in northern
mountains after 12z, spreading to Sierra by 16-18z Tue. Sfc wind
gusts up to 45 kts over higher mountain terrain today. Snow
levels 040 to 060 this morning, lowering 020 to 025 this
aftn/evening.       JClapp


.STO Watches/Warnings/Advisories...
Winter Storm Warning until 6 PM PST this evening for Motherlode-
Northeast Foothills/Sacramento Valley-West Slope Northern Sierra
Nevada-Western Plumas County/Lassen Park.

Freeze Watch from late Wednesday night through Thursday morning
for Central Sacramento Valley-Northern Sacramento Valley.

Winter Weather Advisory until 6 PM PST this evening for Burney
Basin / Eastern Shasta County-Mountains Southwestern Shasta
County to Northern Lake County-Shasta Lake Area / Northern
Shasta County.


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