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802
FXUS66 KSTO 182002
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
102 PM PDT Tue Jun 18 2024

.SYNOPSIS...
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Dry and generally seasonable weather persists through midweek,
with slightly higher daytime relative humidities, better
overnight recoveries, and a switch to an onshore flow pattern by
Wednesday. A warming trend is expected in the late week and into
the weekend.
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Key Points
- Winds will decrease throughout the afternoon today, with onshore
  flow dominating most of the area starting Wednesday.
- Generally seasonable temperatures continue through most of the
  week, with a gradual warming trend late week into the weekend.
- Widespread Moderate HeatRisk is expected from Friday through
  Sunday, with some Major HeatRisk in the foothills on Saturday.

Short-Term Discussion (Today THROUGH Friday)...
Winds continue to trend down this afternoon, as the current low
pressure system moves out of the area and leaves a broader trough
behind it. This broad troughing pattern will bring the return of
onshore flow at the surface on Wednesday, with breezy to gusty
south to west late day winds. The trough will also keep
temperatures near normal for the time of year through Wednesday,
with high temperatures in the Valley expected to be in the high
80s to mid 90s, and in the 70s and 80s at higher elevations. While
daytime humidities will remain in the teens to 20s in the Valley,
overnight recoveries will generally improve due to the onshore
flow.

Late week, both daytime and overnight temperatures begin a
warming trend, with the Valley seeing the likely return of
widespread triple digit temperatures by Saturday as a ridge builds
over the Great Basin and heights over interior NorCal rise.
Widespread Moderate HeatRisk is expected to start Friday and will
continue through the weekend. Currently probabilities of
Sacramento Valley locations (north of Sacramento metropolitan
area) reaching at least 100 degrees on Friday are 50 to 90%. From
the Sacramento metropolitan area and southward into the northern
San Joaquin Valley, chances are generally lower, at 15 to 50%
probability. Temperatures will continue to warm as we move into
the weekend.

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.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...
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Ensemble guidance and cluster analysis indicate hot temperatures
on Saturday from rising heights aloft from ridging over the Great
Basin. This is resulting in widespread Moderate HeatRisk across
the Valley, foothills and mountains on Saturday, with localized
Major HeatRisk in some of the foothill locations. The probability
of high temperatures of 100 degrees or higher in the Valley on
Saturday is 60-90 percent, excluding the Delta where periods of
breezy onshore flow will moderate things. Temperatures then
decrease slightly on Sunday and into next week as troughing moves
into the region. Widespread Moderate HeatRisk continues in the
Valley and foothills on Sunday before retreating to mainly Minor
for much of the area early next week.
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.AVIATION...
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VFR conditions across interior NorCal for the next 24 hours. In
the Valley, decreasing northerly winds, generally less than 12
kts. In the Delta, southwest winds with speeds of 5-15 kts. In the
mountains, expect surface winds from the west becoming easterly
overnight, generally less than 12 kts but with some gusts up to 15
kts.
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.STO WATCHES/WARNINGS/ADVISORIES...
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None.
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$$