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521
FXUS66 KSTO 222045
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
145 PM PDT Sat Jun 22 2024

.SYNOPSIS...
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Hot weather continues through today, with warm and mostly dry
weather then expected through the remainder of the weekend and into
the week ahead. A cool down to near normal temperatures is then
anticipated by the end of the week.
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&&

Key Points

- A Heat Advisory remains in effect through 8 pm this evening as
  high temperatures into the triple digits are expected this
  afternoon within the Advisory area.
- Widespread Moderate HeatRisk is expected today and Sunday, with
  areas of Major HeatRisk today. Areas of Moderate HeatRisk
  remain in the Valley Monday through Wednesday.

Short-Term Discussion (Today THROUGH Tuesday)...
As of early this afternoon, latest GOES-West satellite imagery
shows clear skies across interior NorCal. These clear skies and
generally light winds are allowing temperatures to warm, with most
Valley locations already well into the 90s and upper 70s to 80s
elsewhere. While a south to west breeze will begin to pick up
through the afternoon and early evening hours, high temperatures
are still expected to reach the triple digits throughout the
Valley and adjacent foothills locations and top off in the 80s to
mid 90s at higher elevations. Occasional late day gusts of 15 to
25 mph will be possible through the Valley and Delta, with
strongest winds anticipated within the Delta vicinity.

Moving into Sunday, an upper level trough looks to eject eastward
along the Washington/Canadian border as broad ridging over the
southern CONUS shifts slightly westward. While overall appreciable
impacts are not anticipated, a slight cool down and more widespread
breezy winds will accompany this transient pattern shift. As a
result, widespread moderate HeatRisk today is expected to become
confined to the Valley and foothills on Sunday, with only localized
moderate HeatRisk areas persisting through midweek. Corresponding
high temperatures in the 90s to low triple digits will be possible
across the Valley and foothills, with 70s to 80s at higher
elevations. Otherwise, onshore flow is expected to continue as well,
with breezy to occasionally gusty, late day south to west winds.

Additionally, there is a weak signal within ensemble guidance that a
transient lobe of monsoonal moisture may trek northward to areas
south of the I-80 corridor on Tuesday. This may result in a brief
window for isolated shower or thunderstorm development along the
Sierra on Tuesday afternoon before quickly transitioning eastward
off the Sierra crest. Current probabilities of thunderstorm
development remain around 10 to 15% at this time, but any
thunderstorms that may develop will be capable of brief heavy
rainfall, gusty winds, and lightning.

&&

.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...

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Cluster analysis continues to indicate that generally
southwesterly flow aloft will remain in place through Wednesday.
This will allow for slightly above normal temperatures to persist.
An upper level trough then looks to move through the Pacific
Northwest across the late week period. Resultant lowering heights
will lead to temperatures cooling to near normal for Thursday and
Friday, with primarily low to mid 90s throughout the Valley and
70s to 80s at higher elevations. Ensemble guidance then depicts
some uncertainty in the upper level pattern moving into next
weekend, but is beginning to indicate a gradual warming trend
through the end of the extended forecast period.
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&&

.AVIATION...

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Breezy south to west surface winds (occasional gusts 15-20 kts)
across interior NorCal through 06z. Sustained surface winds then
below 12 kts outside of the Delta overnight. VFR conditions
expected through the forecast period.
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&&

.STO WATCHES/WARNINGS/ADVISORIES...
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Heat Advisory until 8 PM PDT this evening for Central Sacramento
Valley-Motherlode-Mountains Southwestern Shasta County to
Western Colusa County-Northern Sacramento Valley-Northern San
Joaquin Valley-Southern Sacramento Valley.
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&&

$$