720
FXUS66 KSTO 280843
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
143 AM PDT Tue May 28 2024



.SYNOPSIS...
Periods of minor to moderate HeatRisk this week with locally
elevated fire conditions and breezy north winds across the
northern and central Sacramento Valley Thursday. Onshore flow
returns late this weekend into early next week.

&&

.DISCUSSION...
Relatively quiet night across interior NorCal, with light breezes
being observed across the Valley. GOES 18 Satellite reveals some
stratus forming in the Bay/Delta, with some intrusion possible,
mainly for the Delta areas, through the night and into the morning
hours. As we move through the morning today, we can expect
similar temperatures to what we experienced on Memorial Day. An
upper level trough in the PacNW will maintain weak onshore flow
over the area today, with areas near the Delta experiencing winds
of around 10-15 mph, with gusts of 25 mph possible. Strongest
winds are expected in the afternoon hours.

The trough axis will begin to slide over NorCal later today weak
upper level ridging will build in the Eastern Pacific, which will
introduce breezy northerly winds, warm and dry conditions
beginning Wednesday. North winds of around 10-20 mph with gusts up
to 25 mph are possible, mainly along the I-5 corridor. As the
trough moves further east, and ridging continues to build in the
Eastern Pacific, the pressure gradient will tighten some on
Thursday which will allow for stronger northerly winds to
develop. North winds of 15 to 25 mph, with gusts 30 mph or more.
The National Blend of Models (NBM) suggests probabilities of
exceeding 40 mph gusts are around 25-50%, again mainly along the
I-5 corridor. Along with the breezy conditions, dry air will enter
the area, with relative humidity (RH) values forecast to be in
around 10-20% across the entire Valley. Combined with breezy
northerly winds and dry air, elevated fire weather conditions are
anticipated Thursday.

The change in our upper level pattern will lead to warmer
temperatures by midweek. Thursday will see high temps in the low
to mid 90s with 80s and 70s in the higher elevations. Friday will
be the warmest, with NBM probabilities suggesting a 20-60% chance
that areas in the central and northern Sacramento Valley may break
100 degrees, introducing widespread areas of Moderate HeatRisk.
Breezy and dry conditions will persist on Friday as well, with low
RH values once again in the 10-20% range for the Valley, allow
wind gusts will be generally below 20 mph.

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...

On Saturday, we will see a slight lowering of daytime high
temperatures, as an offshore trough will flatten the heights and
promote more onshore flow to the area once again. Generally, high
temperatures will be mid 80s to mid 90s across the Valley, with
the cooler high temperatures in the Delta. Similar temperatures
and conditions are expected on Sunday. As we move into the next
week, the upper level pattern will become more zonal, with
ensembles and Cluster Analysis in relatively good agreement of
this pattern manifesting. This pattern will allow for afternoon
high temperatures to once again climb into the mid and upper 90s
for the Valley, with mid 70s to mid 80s for the higher elevations.
Widespread moderate HeatRisk on Tuesday, with isolated areas of
Major HeatRisk are currently forecast for the central and northern
Sacramento Valley.

Wood

&&

.AVIATION...

VFR conditions next 24 hours. Local southwest surface wind gusts
20-30 kts vicinity west Delta, areas of southwesterly 15-25 kts
in the Sacramento Valley and northern Sierra (northwesterly
across the northern San Joaquin Valley) after 22Z, and generally
less than 12 kts elsewhere.
&&

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

$$