559
FXUS66 KSTO 081924
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1224 PM PDT Sat Jun 8 2024

.SYNOPSIS...
Slightly cooler but still above normal temperatures continue
through the weekend. Warmup expected early next week with Major
HeatRisk for the northern and central Sacramento Valley. Isolated
high elevation mountain shower/thunderstorm chances in the
afternoon/evening hours today and Sunday.

&&

.DISCUSSION...

Key Points

- Minor HeatRisk this weekend with very localized areas of
  Moderate HeatRisk in the northern Sacramento Valley
- An Excessive Heat Watch is in effect for Monday morning through
  Wednesday evening for areas of major HeatRisk throughout
  portions of the Sacramento Valley with widespread triple digit
  highs by Tuesday.
- Local waterways are still running cold and fast from snowmelt

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

For this weekend, slightly cooler but still above normal
temperatures are forecast. Increased onshore flow is helping to
keep temperatures cooler in the Delta and vicinity. Mainly Minor
HeatRisk is expected across the area, with just some isolated
Moderate HeatRisk, mainly around the northern Sacramento Valley.
Valley high temperatures look to be in the upper 80s to mid 90s
this weekend. With increased onshore flow, periods of breezy
conditions are expected this weekend, with onshore gusts of 15 to
25 mph in the afternoon and evening hours, primarily across the
Delta and into the southern Sacramento Valley and northern San
Joaquin Valley.

A weak trough will pass today into Sunday, bringing the potential
for isolated high elevation mountain showers or thunderstorms in
the afternoon and evening. Although there is sufficient lift
across the mountains today, best chances (10-20% chances) for
thunderstorms will be mainly across the Coastal Range and Southern
Cascades areas with marginal chances south of Hwy. 50 beyond our
forecast area. Precipitable water analysis supports this with the
greater influx of moisture being over the Coastal Range and areas
further north and southeast of our forecast area. Sunday will see
chances (10-20% chances) move to the Northern Sierra, across
eastern Plumas and Shasta counties. Be sure to check the latest
forecast conditions if recreating in the afternoon and evening
times this summer.

A warmup is expected for early next week, with widespread Moderate
HeatRisk returning on Monday, and areas of Major HeatRisk in the
northern and central Sacramento Valley and northern San Joaquin
Valley. The NBM currently has Valley highs in the mid to upper 90s
south of Interstate 80, with 100-104 to the north. The heat peaks
on Tuesday, with Valley highs of around 100-107 forecasted,
warmest over the northern Sacramento Valley. Also on Tuesday,
widespread Major HeatRisk in the foothills and much of the Valley,
though the Delta breeze could mitigate this to some extent for
influenced areas. As an result, an Excessive Heat Watch is in
effect for Monday morning through Wednesday evening for the
Sacramento Valley and adjacent foothills with forecasted highs of
95 to 107 possible. Reconsider outdoor activities during the
hottest part of the day (3:00-7:00 PM) and take frequent breaks in
the shade if possible for those outdoors.

A reminder, area waterways continue to run fast and cold from
snowmelt, creating dangerous conditions for those seeking relief
in rivers and lakes next 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

&&

.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...

Ensemble guidance and cluster analysis indicate a closed low over
southern California with some ridging over the West Coast in the
middle of next week. Hot temperatures are forecast to continue on
Wednesday, with the National Blend of Models (NBM) showing a 60
to 90 percent probability of high temperatures reaching or
exceeding 100 degrees in the Valley on Wednesday. For the rest of
the week, ensembles are suggesting a trough approaching and moving
across the west, bringing a relative cool down late-week and into
next weekend. HeatRisk looks to mainly be Minor for the foothills
and mountains, with areas of Moderate in the Valley from Thursday
through Saturday. Valley forecast highs are generally in the 90s
over this timeframe.
&&

.AVIATION...

VFR conditions prevail across interior NorCal over the next 24
hrs. 10-20% probability isolated shower/thunderstorm over the
mountains through 03Z Sunday. Sustained surface winds mainly at
or below 12 kts, except vicinity Delta with southwest winds
10-20 kts and gusts of 15-25 kts through 12Z Sunday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Watch from Monday morning through Wednesday
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.

&&

$$