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
000
FXUS66 KSTO 211232
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
432 AM PST Tue Feb 21 2017

.Synopsis...
Significant flooding concerns continue as runoff from the recent
rain continues to work its way downstream adding stress to
waterways. Showery weather with a few thunderstorms expected into
mid-week, then another stronger storm potentially late in the
weekend.

&&

.Discussion...
Winds have continued to decrease overnight in the valley and have
cancelled the wind advisory, but strong gusty southwesterly winds
continue in the higher elevations of the northern Sierra Nevada
and southern Cascade Range. Precipitation has turned more showery
behind the front with even a few thunderstorms over northern
Shasta County.

Convective precip will continue across the region with overall QPF
expected to be considerably lighter, but flooding concerns will
continue as runoff works its way downstream. Lowering snow levels
to around 3000 to 4000 feet by tonight will also help reduce
runoff.

Next upstream vort is evident on satellite imagery crossing 130W
and will assist in leading to another upswing in shower and
thunderstorm activity by midday. Upslope flow will continue
moderate to heavy snow in the northern Sierra Nevada today with up
to another foot or more of additional accumulation expected above
5500 feet before tapering off this evening.

Transition to northwesterly flow aloft Wednesday will allow much
of the valley to dry out for the second half of the week with only
a few showers remaining over the mountains.

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)
Stormy weather is possible this weekend, with the main issue
being snow causing travel problems.

Extended models are now showing a cold upper trough from western
Canada dropping down along the coast and phasing together with an
upper low from the Gulf of Alaska. If this occurs, this would
bring an extended wet period through the weekend. A secondary low
is currently projected to continue this into Monday and possibly
into Tuesday as well.

Unlike the current system, snow levels are expected to be quite
low with these cold systems, around 2500-3000 feet. Accumulating
snow could be a travel issue Saturday night through Monday night,
potentially extending into the foothills. Uncertainty in the
details remains high, as model runs have been changing quite a
bit. Stay tuned to see how this system develops! EK

&&

.AVIATION...
Pac fntl sys movs thru tngt with shwrs Tue. In Cntrl Vly, wdpsrd
MVFR/IFR conds ovngt with sct MVFR conds Tue in shwrs and isold
aftn tstms. Omtns, wdsprd IFR/LIFR thru Tue mrng bcmg areas
MVFR/IFR Tue aftn. Stg Sly sfc wnds tngt in Cntrl Vly of 25-35kts
with gusts up to 50 kts til arnd 12z Tue. Stg SWly wnds omtns tngt
and Tue with gusts up to 60 kts or gtr ovr hyr trrn. Sn lvls abv
060 tngt lwrg to arnd 040-050 Tue aftn.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 10 PM PST this evening 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.