Cold in California, May 4, 2019

Area Forecast Discussion
National Weather Service Sacramento CA
300 PM PDT Sat May 4 2019

.SYNOPSIS...
Mountain showers and thunderstorms possible Sunday into next
week. Cooling trend Sunday into early next week, then warming
trend by the middle of next week.

&&

.DISCUSSION...
Quiet weather this afternoon across interior NorCal ahead of an
approaching closed low off the CA coast. Temperatures this
afternoon are generally 2 to 5 degrees cooler compared to
yesterday's near the Delta influenced areas. With a deepening
marine layer, hi-res guidance is indicating the potential for
some stratus to advect into the southern Sac Valley Sunday morning
if winds through the Delta remain gusty overnight.

Precipitation chances will increase Sunday afternoon as upper low
gradually moves inland into Central CA. While shower activity
will be mainly focused over higher terrain, some of these showers
could spread over the southern Sacramento and northern San
Joaquin valleys late Sunday into early Monday. High resolution
guidance points toward the potential for convection over higher
terrain during the afternoon and early evening hours, especially
over the Sierra. Models also promote thunderstorm development
over the higher terrain Monday afternoon as the upper system
slowly shifts eastward. Mountain showers or thunderstorms could
persist into Tuesday.

Temperatures will return to near or below normal Sunday into
early next week; less cooling expected across the northern areas.
Look for highs to reach the low 70s to mid 80s across the Valley,
with 50s to 60s over the mountains through Tuesday.

&&

.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)

A blocking upper ridge situated over the eastern Pacific will
support a persistent area of lower heights to settle over
portions of the West Coast. These will come in the form of upper
lows which pivot back from the Central Great Basin back toward the
southwestern U.S. Moisture generally is lacking in these "Inside
Slider" type systems which will focus any convective activity back
toward the higher terrain. Thus, expect diurnally forced showers
and thunderstorms each afternoon and evening. Based on the current
track of these closed lows, the better concentration of shower
activity should fall from I-80 southward. As the last in the trio
of systems dives down toward northern Baja California next
Saturday (5/11), the upstream/offshore ridge will likely expand
inland into the Pacific Northwest. The resultant dry
northeasterly flow aloft should encourage a shift to drier
conditions. Reliable ensemble systems agree on this pattern
change, but with variable forecast details. Regarding
temperatures, numbers should be around, or slightly above
climatology as Valley highs stay in the 80s. The exception being
the upper Sacramento Valley with daily highs in the low 90s. ~BRO

&&

.AVIATION...

Expect VRF conditions across all TAF sites through Sunday morning.
Winds will be variable at times and generally remain below 10
knots. Some stratus expected from Sacramento southward by 12Z
Sunday but not anticipating any issues with ceilings.  ~BRO

&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&