243
FXUS66 KSTO 300917
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
217 AM PDT Thu May 30 2024

.SYNOPSIS...

Elevated fire risk today due to breezy northerly winds and low
humidity values. Warming trend continues, with Friday expected to
be the warmest day. Slight cooldown Saturday through Monday, then
chances increase for triple digit high temperatures through the
week.

&&

.DISCUSSION...

Upper level troughing continues to move eastward this morning
extending into the northern Great Plains, and upper level ridging
is building in eastern Pacific. As the trough continues to move
eastward, our heights will be orientated in a northwesterly
pattern, which will lead to locally breezy conditions and low
relative humidity (RH) values today. Strongest northerly winds
will once again be in the northern and central Sacramento Valley,
along the I-5 corridor with wind speeds of 10-20 mph and gusts up
to 30 mph possible. Strongest winds are expected this morning and
afternoon, before easing in the early evening hours. Low RH
values of 10-20%, combined with the breezy northerly winds will
lead to elevated fire weather conditions to exist once again for
the Valley today. High temperatures will climb into low to mid 90s
for the Valley as well, leading to Moderate HeatRisk for the
Valley.

On Friday, the upper level ridge moves inland and will lead to an
increase in high temperatures around the Valley into the mid to
upper 90s, with around a 30-50% chance of breaking 100 for the
central and northern Sacramento Valley. Onshore flow should keep
the Delta in the low 90s for high temperatures. Widespread
Moderate HeatRisk will overtake the northern/western Sacramento
Valley, while the Delta will remain in Minor HeatRisk. RH values
will still be in the 10-20% range for the Valley, but wind speeds
will be lower and west-south winds will overtake the area Friday
afternoon. Weak upper level troughing is then progged to move
through the PacNW and extend into NorCal on Saturday, which will
reduce high temperatures slightly on Saturday and Sunday, with low
to mid 90s for the Valley, mid 80s for the Delta, and cooler
upper 60s to low 80s for the foothills and mountains. Most of the
forecast area will be in Minor HeatRisk, with isolated spots of
Moderate HeatRisk, mainly from Yuba City north into Redding. Upper
level troughing is then forecast to build in the Gulf of Alaska,
and flatten our heights out into a more zonal pattern late Sunday.

&&

.EXTENDED DISCUSSION (Monday THROUGH Thursday)...

On Monday, a trough will eject from a closed low in the Gulf of
Alaska into Alberta and keep our upper level height pattern in a
zonal component. The westerly flow aloft will help cool things
down from Sunday`s temperatures, with the Valley being in the
upper 80s to low 90s and low 60s to low 80s in the foothills and
mountains. Tuesday is when the area will experience a warmup in
temperatures, as an upper level ridge is forecast to build over
NorCal, increasing the heights and increase our temperatures. Much
of the Valley will experience mid to upper 90s Tuesday, with the
Delta remaining in the low 90s as the high pressure strengthens.
Most of the Valley will be in Moderate HeatRisk on Tuesday, with
isolated Major HeatRisk around Chico.

Wednesday and Thursday we will continue to see our upper level
ridge strengthen over the area, which will continue to allow high
temperatures to climb. Wednesday high temperatures are currently
forecast to range from the upper 90s to the mid 100s across the
Valley, with 70s to low 90s for the higher elevations. National
Blend of Models (NBM) probabilities of reaching 100 degrees are
currently around 65-95% for the Valley. Overnight recoveries on
Tuesday night will be in the low 70s for the northern Sacramento
Valley and mid to upper 60s for the central and San Joaquin
Valley`s. These high temperatures will also introduce widespread
Major HeatRisk across the Valley, mainly for areas north/northeast
of I-80. Major HeatRisk affects everyone without effective
cooling and/or adequate hydration, so make sure if you are outside
for extended periods of time to have hydration and a place to
escape the heat.

A similar situation regarding heat/temperatures will exist on
Thursday, with temperatures expected to be in the upper 90s to mid
100s for the Valley, with the hotter temperatures in the northern
Sacramento Valley. Cluster Analysis reveals fairly high
confidence in this pattern manifesting, and possibly lasting
beyond the extended forecast period. The Climate Prediction Center
(CPC) has placed our area under high probabilities (70-80%) of
above normal temperatures in the 8-14 Day Temperature Outlook.

&&

.AVIATION...

VFR conditions next 24 hours. Areas of northerly surface wind
gusts 25 kts in the Sacramento Valley until about 00Z Friday.
Lighter winds elsewhere.

&&

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

$$