996
FXUS66 KSTO 270818
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
118 AM PDT Mon May 27 2024

.SYNOPSIS...
Warm weather continues, with minor HeatRisk through midweek,
transitioning to moderate HeatRisk late week. Weak onshore flow
through Tuesday then shifts to breezy, to occasionally gusty,
northerly surface flow mid to late week, with onshore flow returning
by the weekend. Elevated fire weather concerns for the northern
and central Sacramento Valley Thursday.

&&

.DISCUSSION...
Another quiet overnight period is ongoing for interior NorCal as we
move into Memorial Day. Cloud cover is currently nonexistent, but
onshore flow is a bit stronger than last night, which should result
in early morning low temperatures returning to the low to mid 50s,
with a handful of 40s at higher elevations. Heights aloft are
beginning to rise though as an upper level ridge begins to amplify
across the Great Basin and Intermountain West through the early week
period. Interior NorCal still looks to remain primarily influenced
by broad troughing as an upper level trough tracks toward the
Pacific Northwest Tuesday into Wednesday.

The resultant appreciable weather pattern will remain warm and
mostly dry for today and Tuesday, with some late day breeziness from
the Delta breeze. High temperatures this afternoon look to reach the
upper 80s to low 90s in the Valley, with 70s to low 80s at higher
elevations. A few late day, isolated storms along the Sierra crest
south of Highway 50 will also be possible (10-15% chance), but
should move off of the crest relatively quickly. As the
aforementioned trough moves toward the Pacific Northwest on Tuesday,
onshore flow should be a little breezier, which will limit Valley
high temperatures to the mid to upper 80s for Tuesday afternoon.

The upper level trough then begins to eject eastward Wednesday into
Thursday while ridging aloft amplifies offshore. This is expected to
result in the return of dry, northerly flow to the region from
Wednesday into the late week period. A warming and drying trend is
anticipated, with Valley temperatures well into the 90s on Thursday
and Friday. Friday looks to be the warmest day of the week, with
some 20% to 40% probabilities of reaching the triple digits in the
Sacramento Valley. This will result in some fairly widespread areas
of moderate HeatRisk through the late week period. Additionally,
Thursday could see some gusty northerly winds, particularly across
the northern and central Sacramento Valley, with 35% to 55%
probabilities of gusts exceeding 40 mph at this time. Afternoon
minimum RH values into the low to mid teens, with a few localized
instances of single digits, will likely result in a period of
elevated fire weather concerns where the driest conditions and
gustiest winds overlap on Thursday.

&&

.EXTENDED DISCUSSION (Saturday THROUGH Monday)...
Ensemble guidance continues to show fairly uniform agreement in
the upper level pattern across the weekend and into early next
week. The transient ridging aloft on Friday looks to flatten by
Saturday, with broad troughing again building in across the west
coast. This will result in continued warm temperatures, but a
comparative cool down from firmly in the 90s in the Valley on
Friday, to the upper 80s to mid 90s from Saturday into next week.
Widespread moderate HeatRisk shrinks to scattered areas throughout
the central and northern Sacramento Valley, with primarily minor
HeatRisk then anticipated across the weekend for most. The return
of onshore flow is expected to facilitate this relative cool down
with periodically breezy late day south to west winds.

&&

.AVIATION...
VFR conditions next 24 hours. Local southwest surface wind gusts
15-25 kts vicinity west Delta, generally less than 12 kts
elsewhere.

&&

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

$$