346
FXUS66 KSTO 250833
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
133 AM PDT Sat May 25 2024

.SYNOPSIS...
One more day of cooler weather is expected today, before
temperatures warm back up to near to slightly above normal with
areas of minor HeatRisk from Sunday into the week ahead. Onshore
flow looks to persist through midweek before dry, northerly flow
returns across the late week period.

&&

.DISCUSSION...
A few mid level clouds are evident over the northern Sierra early
this morning as an upper level trough continues to progress from the
Pacific Northwest toward the Intermountain West. This is inducing
onshore flow at the surface as well, with some gusts of 25 to 30 mph
possible throughout the Delta and its vicinity this morning. This
comparatively moister south to west surface wind will also allow for
the introduction of some mid to low level stratus across portions of
the Delta and southern and central Sacramento Valley through this
morning as well.

With the cool and at least partly cloudy start to the morning,
afternoon temperature recovery is expected to be limited. As a
result, Valley high temperatures look to remain firmly in the 70s,
with 50s to 60s at higher elevations. Breezy south to west winds
also look to prevail. This onshore flow pattern is expected to
continue, but as the upper trough remains on its eastward
trajectory, surface winds are expected to slacken overnight into
Sunday. With this transition aloft, heights are expected to rise
on Sunday as upper level ridging then builds in over the western
CONUS. High temperatures by Sunday afternoon look to rapidly jump
up to near normal, with Valley high temperatures in the mid to
upper 80s and 60s to mid 70s at higher elevations.

Despite the building ridging aloft, the ridge axis is expected to
remain generally displaced eastward over the Intermountain West.
Additionally, a closed low digging toward the Pacific Northwest at
the same time will work to induce broad troughing across interior
NorCal as well. While a slight warming trend is expected, this will
effectively limit the upper bound of high temperatures for the early
week period. Resultant high temperatures for Memorial Day look to
reach the upper 80s to low 90s in the Valley and 70s to low 80s at
higher elevations, with similar values anticipated on Tuesday.

&&

.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...
Some notable uncertainty is then present in the forecast across
the mid to late week period. Latest cluster analysis is leaning
toward (~60% of ensemble membership) a solution of ridging aloft
building in through the late week period, while still nonzero
membership (~40%) indicates a continuation of broad troughing
aloft. While the overall differences would be somewhat subtle, the
former solution would result in dry northerly surface flow
returning and temperatures warming through the end of the week. In
contrast, the latter solution would yield a more or less stagnant
weather pattern with onshore flow persisting and temperatures
remaining slightly above normal. This is all to say that, overall
warm, dry, and breezy conditions are expected to prevail through
the extended, but that there is some forecast uncertainty, with a
roughly 10 degree variance in current forecast high temperatures.

&&

.AVIATION...
Mainly VFR conditions next 24 hours, except possible MVFR/IFR in
marine stratus from about 11Z-17Z (50-90% probability in the Delta
and the Sac Valley south of Chico and north of Stockton). Winds
generally less than 10 kts through 23z then delta breeze increases
with southwest wind gusts 20-25 kts in the Delta, Sacramento
Valley, and west-northwesterly 15-25 kts across the northern San
Joaquin Valley.

&&

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

$$