Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 290756

Area Forecast Discussion
National Weather Service Sacramento CA
1256 AM PDT Mon May 29 2023

Isolated to scattered shower and thunderstorm chances continue
for the mountains, portions of the foothills, and northern half
of the Sacramento Valley through Tuesday, then mainly in the
southern Cascades/northern Sierra the rest of the week.
Temperatures will remain near or slightly below normal for much of
this week, followed by slight warming late-week into the weekend.
Periods of locally breezy onshore winds.


GOES-West geocolor satellite imagery illustrates the center of the
low spinning just off the coast of the Bay Area early this
morning, as well as some mid to high clouds over portions of
interior northern California, and marine status to our west.
Locally breezy onshore winds are being observed in the vicinity of
the Delta, and into portions of the southern Sacramento Valley,
with Fairfield/Travis Air Force Base (KSUU) reporting 30 mph
gusts out of the southwest as of midnight. The low will continue
to move southward today, and then will be shifting inland. Another
trough will deepen behind it and bring continued seasonably cool
temperatures and higher elevation shower/thunderstorm chances.

Near to below normal temperatures will continue for most of area
in the short-term forecast. For today, the Valley and lower
foothills can expect daytime highs to approach the mid 70s to mid
80s, and the 50s to 70s for the upper foothills and mountains.
Another round of locally breezy onshore winds will allow for those
cooler temperatures in the Delta area where highs will be
relatively cooler, in the mid 60s to mid 70s. Similar conditions
are expected through mid-week, then a few degrees warmer on

Isolated to scattered shower and thunderstorm chances return
later today, with continued chances over the next several
afternoons and evenings. The best chances today and Tuesday will
be in the southern Cascades and northern Sierra Nevada
mountains and foothills (20 to 45 percent probability of
thunderstorm development) as well as the Coastal Range and
portions of the northern Sacramento Valley (15 to 25 percent
probability of thunderstorm development). For today and Tuesday,
the HREF suggest CAPE values in those areas up to 500 to 1500
J/kg. For the rest of the week, those thunderstorm chances are
mainly up in the mountains of the southern Cascades and northern
Sierra Nevada.The main concerns with any thunderstorms that
develop would be dangerous lightning, hail, downpours, and gusty
winds, which could impact outdoor recreationists. Motorists
should slow down and use wipers/headlights when encountering slick
roads. //KH


There is still some uncertainty in the ensemble guidance and
cluster analysis for the extended forecast period, however the
models seem to be favoring the influence of weak ridging Friday
and Saturday and with a low pressure area over the Gulf of Alaska.
Warmer temperatures are forecast to return, to near normal or
slightly above normal, as well as continued isolated
shower/thunderstorm chances in the mountains (mainly High-Sierra).
For Sunday into early next week, a low pressure trough stretches
down near the California coast. The National Blend of Models (NBM)
advertises a 50 to 85 percent probability of portions of the
Sacramento Valley to reach 90 degrees for the daytime high on
Friday/Saturday with the best chances in the Northern/Central
Sacramento Valley, and a 50 to 95 percent probability on Sunday
for most of the Valley. Areas of moderate heat risk are currently
forecast to return this weekend, mainly in portions of the
northern and central Sacramento Valley.


VFR conditions are generally forecast to prevail over the next 24
hours. Local MVFR conditions associated with showers and/or
thunderstorms, mainly over mountains. MVFR/IFR conditions possible
in stratus vicinity of Delta through 18Z Monday. Low stratus may
push eastward into the Sacramento area terminals between 10Z-16Z
Monday. Gusty and erratic winds expected near thunderstorms.
Surface wind generally at or below 15 kts except vicinity of Delta
with southwesterly wind up to 25 knots.




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