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451
FXUS66 KSTO 232038
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
138 PM PDT Sun Jun 23 2024

.SYNOPSIS...
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Seasonably warm and periodically breezy weather persists across the
early week period, with a slight cooling trend to near normal from
mid to late week and into next weekend.
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&&

Key Points

- Widespread Moderate HeatRisk is expected today.
- Decreasing areas of Moderate HeatRisk remain in the Valley
  Monday through Tuesday.
- Temperatures cool to near normal by the end of the week, with a
  new warming trend possible late in the weekend.

Short-Term Discussion (Today THROUGH Wednesday)...

GOES-West continues to show clear skies across interior NorCal early
this afternoon as temperatures are once again warming into the 90s
in the Valley and adjacent foothills and 80s at higher elevations. A
bit stronger of a south to west breeze is ongoing today as well,
with a few localized gusts of 20 to 25 mph possible into the early
evening. This breeze should keep high temperatures by days end a few
degrees cooler than yesterday as moderate HeatRisk persists
throughout the Valley and foothills today. Corresponding high
temperatures still look to reach the mid 90s to low triple digits
across the Valley and adjacent foothills, with 80s to 90s
anticipated at higher elevations.

Moving into the early week period, an upper level trough looks to
approach the Pacific Northwest while broad ridging over the southern
CONUS gradually retrogrades toward the Desert Southwest. While the
overall flow pattern aloft for interior NorCal will remain largely
unchanged, the intersection of these features will allow a lobe of
monsoonal moisture to advect northward toward interior NorCal late
Monday into Tuesday. The stagnant flow pattern will keep
temperatures seasonably warm, 90s to low triple digits in the Valley
and foothills and 80s to 90s at higher elevations, through Tuesday.
The moisture advection into the region will allow for the potential
to see some isolated thunderstorm development along the Sierra,
generally south of the Highway 50 corridor on Tuesday. Current
probabilities for thunderstorm development are around 10 to 25% in
this area and any thunderstorms that may develop will be capable of
gusty winds, brief heavy rainfall, and lightning which may lead to
new fire starts before rapidly transitioning eastward off of the
Sierra crest.

By Wednesday, the Pacific Northwest trough is expected to gradually
near the coast as the aforementioned broad troughing begins to break
down. This will begin a slightly more ambitious cool down from
Wednesday into the remainder of the week. Wednesday afternoon high
temperatures still look to reach the upper 80s to 90s throughout the
Valley and adjacent foothills, with 70s to 80s at higher elevations.
Resultant HeatRisk looks to fall primarily into the minor category.
Otherwise, breezy to occasionally gusty, late day, south to west
winds are anticipated as onshore flow persists.

&&

.EXTENDED DISCUSSION (Thursday THROUGH Sunday)...

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Cluster analysis is in generally good agreement on the Pacific
Northwest trough transitioning eastward rather rapidly, leaving
predominantly southwesterly flow aloft in its wake over interior
NorCal from late week into next weekend. As a result, high
temperatures are expected to remain near normal by late June
standards, with onshore flow persisting. Some minor day to day
fluctuations in temperatures will be possible, but overall upper
80s to 90s look to prevail in the Valley and adjacent foothills,
with 70s to 80s at higher elevations. Additionally, there are some
hints at a warming trend late in the weekend, but ensemble
guidance is indicating a fair bit of uncertainty regarding the
upper level pattern and attendant appreciable impacts at this
time.
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&&

.AVIATION...

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VFR conditions prevail across interior NorCal next 24 hours.
Breezy south to west winds, with occasional gusts to 20 kts,
expected through 02z Monday. Southwesterly gusts to 20 kts persist
overnight in the Delta and vicinity, with light and variable
winds elsewhere.
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&&

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

&&

$$