Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 201030
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
330 AM PDT Mon May 20 2019

.SYNOPSIS...
Another weather system will impact northern California later today
into Tuesday bringing more rain and mountain snow. Below-average
temperatures continue through the week with additional mountain
shower chances.

&&

.DISCUSSION...
Clear to partly cloudy skies cover the region early this morning
as short-wave ridging provides a brief lull in the unsettled
weather. Current temperatures are chilly ranging from the mid 20s
to mid 30s in the mountains to the mid 40s to lower 50s across the
Central Valley.

Next upstream system seen on satellite imagery crossing inside of
140W north of 40N will move southeast today and approach NorCal by
later in the afternoon. Increasing instability and surface
convergence may lead to a few showers and thunderstorms across
the far northern portion of the forecast area late in the day into
this evening.

More widespread shower activity will spread across NorCal later
tonight and Tuesday as the front surges southward. Showers will
continue Tuesday night in the unstable post-frontal airmass. Most
of the shower activity on Wednesday and Thursday is expected over
the northern Sierra Nevada, but northeasterly flow may allow some
showers to drift down into the foothills and eastern edge of the
Central Valley.

Another shot of snow is expected for the northern Sierra late
tonight through Tuesday, and a winter weather advisory has been
posted.

Temperatures will remain well below average early this week, but
are expected to moderate somewhat by mid-week.

&&

.EXTENDED DISCUSSION (Friday THROUGH Monday)
Unsettled weather looks to continue through much of the extended
forecast periods as a series of low pressure systems move through
Interior NorCal. Best chances for showers looks to be over the
foothills and mountains. Below normal temperatures expected Friday
into Monday with high temps upwards of 5 to 10 degrees below
normal next weekend.

&&

.AVIATION...
Lcl MVFR/IFR conds poss in shwrs, mnly ovr fthsl/mtns, otrw VFR
conds thru 00z Tues ovr Intr NorCal. Isold MVFR/IFR vsby poss in
Srn Sac/Nrn San Joaquin vly in br/fg til 17z Mon. Isold aftn tstm
poss in Nrn Sac vly and adjcnt fthls. Conds dtrtg tngt ovr Intr
NorCal with areas MVFR/IFR, mnly ovr fthls/mtns aft as nxt Pac stm
movs inld. Areas of Sly sfc wnd gsts to 25 kts aft 22z tda in
Cntrl Vly contg into tngt. SWly sfc wnd gsts to 35 kts ovr hyr mtn
trrn this aftn into tngt.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from midnight tonight to 8 PM PDT
Tuesday for West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.

&&

$$



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