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367
FXUS66 KSTO 050932
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
232 AM PDT Wed Jun 5 2024


.SYNOPSIS...
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Widespread Major HeatRisk and well above normal temperatures are
expected today across interior NorCal. Moderate HeatRisk with
broad areas of Major HeatRisk expected Thursday. Cooler, but
still seasonably warm, weather expected heading into the weekend.
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.DISCUSSION...

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Key Points
- An Excessive Heat Warning remains in effect through 8 PM PDT
  Thursday evening across the Valley and adjacent foothills.
- Hottest day of the week today: Widespread MAJOR HeatRisk, triple
  digit temperatures, and elevated overnight lows. Reconsider
  outdoor activities during the hottest part of the day (3:00-7:00
  PM).
- Areas of Major HeatRisk continue on Thursday, with Moderate
  HeatRisk by Friday; Triple digits in the Northern and Central
  Sacramento Valley and adjacent Valley foothills with mid to
  upper 90s in the Delta and Sacramento metro area.

Short-Term Discussion (Today THROUGH Saturday)...
The first heat event of the year is here and so are the elevated
overnight temperatures! Just after midnight (as of 2:22 am),
temperatures in the Delta & Valley are in the low 70s-low 80s,
meanwhile in the foothills & mountains are in the upper 50s-mid
70s.

These H-O-T, HOT(!) temperatures continue today, with widespread
Major HeatRisk and triple digit daytime highs. Heights aloft continue
to rise over the western CONUS as a strong high-pressure ridge
sets up shop over Northern California. Major HeatRisk will cover
the majority of the Sacramento Valley & foothills on Thursday, as
a result, an Excessive Heat Warning remains in effect for the
Valley and foothills through 8 PM PDT Thursday. Breezy north to
west winds are expected to increase throughout the day today, but
will not be as strong as yesterday`s breezes.

As the ridge pushes eastward towards the Great Basin and
Intermountain West throughout the rest of this week, more
elongated troughing will work to replace it. Northern California
will be under southwesterly flow aloft which means increasing
onshore flow is expected late Thursday-Saturday. We`ll begin to
see the return of Moderate HeatRisk across the region by Friday
as the Delta breeze fights valiantly against the heat. While the
majority of the Valley & Delta will experience only-slightly
elevated overnight lows, the northern Sacramento Valley and
elevations generally above 2000 ft will see overnight temperatures
10-20 degrees above-normal (15-20 degrees in the mountains).
Additionally, this flow pattern aloft will at least introduce some
low end potential (5% to 15% chance) for isolated shower or
thunderstorm activity along the Sierra crest south of the Highway
50 corridor with a 10-15% chance in far western Tehama and Shasta
counties on Thursday.

Area waterways continue to run fast and cold from snowmelt,
creating dangerous conditions for those seeking relief in rivers
and lakes next week. Remember to practice heat and cold water
safety this week!

To view the latest HeatRisk, please visit
www.wpc.ncep.noaa.gov/heatrisk/

To view current water temperatures, please visit
www.cnrfc.noaa.gov
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.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)...
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Upper trough along the CA coast progged to form closed upper low
Sunday as it digs offshore. Meanwhile EPAC upper ridge builds into
the W Coast through early next week. Warming will result Sunday
into Tuesday with above normal temperatures. Triple digit heat in
the N Sac Valley Sunday, expands through much of the Sac Valley
Mon/Tue. Weak Delta cooling expected to keep high temps below the
century mark in the S Sac Valley. Offshore closed upper low nudges
slightly closer to the CA coast midweek allowing for minor
deepening of marine layer. This will result in additional slight
cooling in Delta breeze influenced areas, but highs in S Sac
Valley remain around 10 degrees above normal. Triple digit highs
continue in the northern and central Sac Valley Wednesday with
mostly 80s to lower 90s for the mountains and foothills.
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&&


.AVIATION...
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VFR conditions over interior NorCal next 24 hrs with
sfc wind mainly at or below 12 kts except vcnty of Delta aft 00z
Thu SWly sfc wind up to 20 kts.
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&&

.STO WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM PDT Thursday 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.

&&

$$