278
FXUS66 KSTO 010900
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
200 AM PDT Sat Jun 1 2024

.SYNOPSIS...
Slight cooldown Saturday through Monday before the return of
100s in the Valley Tuesday through Friday. An Excessive Heat
Watch has been issued for the Valley from Tuesday morning until
Thursday evening. Hottest temperatures expected Wednesday. Slight
chance of showers for the Coastal Range Monday late morning.

&&

.DISCUSSION...

Discussion at a Glance
- Cooler Saturday-Monday with increased onshore flow and Delta
  Breeze.
- An Excessive Heat Watch has been issued from Tuesday morning to
  Thursday evening across the Sacramento Valley and adjacent
  foothills.
- Areas of Major HeatRisk Tuesday for the Valley, becoming
  widespread Wednesday & Thursday for the Valley & Foothills with
  widespread triple digit high temperatures. Prepare now for
  elevated daytime highs and overnight lows and reconsider
  outdoor activities during the hottest part of the day (3:00-7:00
  PM).
- Moderate HeatRisk next Friday, with a few isolated spots of
  Major HeatRisk in the Valley; Triple digits in the Northern
  Sacramento Valley and adjacent Valley foothills with low to mid
  90s in the Delta and Sacramento metro area

Short-Term Discussion

Saturday`s weather looks to give a minor reprieve with
temperatures 5-8 degrees cooler than Friday ahead of our
impending warm up early next week. An upper level trough is
sliding over Northern CA this morning apart of a larger level low
moving through the Pacific NW. This will help cool the area and
keep onshore flow apart of the forecast through Monday.
Afternoon highs will generally be in the upper 80s and low 90s in
the Valley, with coolest temperatures expected on Monday. This
weekend will be fairly quiet with generally clear skies and
marginal areas of Moderate HeatRisk in the foothills and portions
of the Northern Sacramento Valley. Each afternoon will see the
Delta Breeze strengthen with west gusts of 15-25 MPH, tapering off
through the following mornings.

As the weather system moves through the Pacific NW, it will bring
general cloudiness to the area and a 20-40% chance of
precipitation across the Coastal Range and Southern Cascades.
There is only a 15-25% chance of amounts over 0.10", so all
indicators show that if anything were to develop it will be a
minor amount of precipitation. Ultimately, it will remain over
the mountains, keeping the Valley and much of the Sierra dry.
Monday will the coolest day of the 3 day stretch with Valley
highs in the mid 80s with 70s and 60s across the foothills and
mountains respectively.

&&

.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...

Tuesday will see upper level ridging moving inland, increasing
heights and temperatures around the region. Daytime high
temperatures in the low 100s for the Valley, with widespread
areas of Major HeatRisk in the Valley and extending into the
foothills and portions of the Delta. National Blend of Models
(NBM) probabilities of reaching 100 for the area are around 50-85%
on Tuesday. Peak temperatures are expected Wednesday with the
ridge firmly over the area, with hot temperatures continuing
Thursday. An Excessive Heat Watch has been issued from 11 am
Tuesday to 8 pm Thursday with temperatures of 95 to 107
forecasted. The Delta Breeze could bring some slightly less hot
weather to influenced areas, and how strong this effect will be
should become more clear over the next few days.

Major HeatRisk affects everyone without effective cooling and/or
adequate hydration. Consider canceling outdoor activities during
the heat of the day. Clusters show there is some uncertainty
between ensembles over the strength and location of the ridge late
in the week. As a result the NBM has a large spread between the
25th and the 75th percentiles, which means a large range of
possible high temperatures for late in the week and into the
following weekend with a 10-12 degree difference in solutions.
Currently widespread Moderate HeatRisk is expected for Friday,
with isolated Major HeatRisk for the Valley/foothills.

&&

.AVIATION...

VFR conditions expected over the next 24 hours. Sustained surface
winds under 12 kts except winds 15 to 25kts in the Delta.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Watch from Tuesday morning through Thursday
evening for Carquinez Strait and Delta-Central Sacramento Valley-
Motherlode-Mountains Southwestern Shasta County to Western
Colusa County-Northeast Foothills/Sacramento Valley-Northern
Sacramento Valley-Northern San Joaquin Valley-Shasta Lake Area /
Northern Shasta County-Southern Sacramento Valley.

&&

$$