430
FXUS66 KSTO 212101
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
201 PM PDT Fri Jun 21 2024



.SYNOPSIS...
Dry weather continues. The hottest temperatures of the week are
expected tomorrow with widespread triple digits, moderate
HeatRisk, with areas of Major HeatRisk. Begining Sunday,
temperatures will cool off slightly next week, but will remain
above-normal.

&&

Key Points:
- Widespread Moderate HeatRisk is expected today through Monday,
  with areas of Major HeatRisk today-Saturday
- A Heat Advisory is in effect from 11 am to 8 pm Saturday with
 Widespread Moderate HeatRisk and areas of Major HeatRisk in the
 Valley and foothills on Saturday; Highs in the triple digits.

Short-Term Discussion (Today THROUGH Monday)...
Ensembles and clusters remain in good agreement that we will
transition to upper level ridge will begin over NorCal today
resulting in warmer high temperature. The ridge will amplify over
the weekend, as an upper high strengthens over the Desert
Southwest. This will cause temperatures to heat up to well above
normal levels from the upper 90`s to low 100`s today. Widespread
triple digit heat is expected Saturday with Central Valley and
lower foothill highs 100-106. Cooler Delta air will modify the
late afternoon high temperatures over the Delta, and portions of
the southern Sacramento Valley keeping most of these areas in
moderate HeatRisk versus major to the north and over the
foothills. Increasing southwest flow is expected over NorCal
Sunday, as a trough moves through the Pacific Northwest. This will
likely initiate an afternoon Delta breeze with high temps a few
degrees cooler in the upper 90`s and low 100`s.

Widespread Moderate HeatRisk expected through Monday, with areas
of Major HeatRisk today and Saturday mainly over the Sierra
foothills & northern Sacramento Valley. The National Blend of
Models (NBM) is indicating a 80-100% chance of temperatures
greater than 100 degrees F throughout most of the Valley on
Saturday.

By Sunday, a trough is expected to move through the Pacific
Northwest resulting in increased southwesterly flow. This will
translate into a more robust Delta breeze on Sunday with gusts
15-25 mph through the Valley. Slightly cooler temperatures will
follow, but Moderate HeatRisk is expected to continue across most
of the Valley and foothills through Monday.

&&


.EXTENDED DISCUSSION (Tuesday THROUGH Friday)...
Ensemble guidance favors a continuation of broad troughing and
anomalously high heights aloft across interior NorCal through
midweek. This will keep high temperatures slightly above normal
for Tuesday and Wednesday, with 90s to low triple digits
throughout the Valley and foothills and 80s to 90s at higher
elevations. Despite this, onshore flow is expected to persist,
with breezy to gusty late day south to west winds. Moving toward
the latter half of the week, cluster analysis is in good agreement
on an upper level trough progressing through the Pacific
Northwest. There is some uncertainty with respect to the exact
details on how this trough will evolve, but there is increasing
confidence that a slight cool down to near normal temperatures
will accompany this feature for Thursday and Friday.


&&

.AVIATION...
VFR conditions across interior NorCal over the next 24 hours.
Sustained wind will generally be below 12 kts, with the exception
being the Vicinity Delta where sustained southwesterly winds up to
15kts with gusts 15-20 kts are expected between 22z Friday-08z
Saturday. Additionally, there is a 20-40% chance of marine low
stratus intrusion west of Fairfield.


&&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM to 8 PM PDT Saturday for Central
Sacramento Valley-Motherlode-Mountains Southwestern Shasta
County to Western Colusa County-Northern Sacramento Valley-
Northern San Joaquin Valley-Southern Sacramento Valley.

&&

$$