Excessive Heat in California, July 9 to 12, 2021

Area Forecast Discussion
National Weather Service Sacramento CA
200 PM PDT Fri Jul 9 2021

.SYNOPSIS...
Dry conditions are forecast to continue with very hot temperatures
expected through the weekend and continuing into early next week. An
Excessive Heat Warning is in effect for much of interior NorCal
through Monday evening when the hottest weather is expected.

&&

.DISCUSSION...
It's here. The heatwave has arrived.

Temperatures across the Central Valley are soaring well into the
triple digits this afternoon. As of 1 PM, most airports are
running anywhere from 5 to 13 deg F warmer compared to 24 hours
ago. Highs will likely eclipse 110 deg F in parts of the northern
Sacramento Valley by the time the afternoon wraps up. Excessive
Heat Warning went into effect for nearly the entire area at noon
today, and continues through Monday evening.

Powerful upper level ridge will bring continued warming into the
weekend when the heatwave is forecast to peak. Widespread 110s are
increasingly more likely up and down most of the Sacramento
Valley for Saturday and Sunday. With 850 mb temps in the 30 to 32
deg C range, surface temps in some of the hottest places in the
Sacramento Valley -- such as Redding and Red Bluff -- could
conceivably make a run for 116 deg F. Downtown Sacramento may
approach its all-time record high is 114 deg F, set on July 17,
1925. According to the National Blend of Models, there is a 10%
chance that Sacramento would at least tie this tomorrow.

An often overlooked heatwave element is the overnight low temp.
Present forecast calls for much of the Valley and adjacent
foothills to only cool to the 70s to middle 80s. This lack of
cooling will only exacerbate the heat-related impacts.
Consequently, widespread very high risk blankets the Valley this
weekend.

Some minor relief will likely arrive to the Delta area and
Sacramento Metro Area on Monday as onshore winds return. This
will drop highs to the middle 90s to low 100s. Farther north --
away from the Delta-influenced breeze -- Redding and Red Bluff
will still hover around 110 deg F.

Heat is the number one weather-related killer in the United
States. Please take action to stay safe during this dangerous
heatwave. // Rowe

&&

.EXTENDED DISCUSSION (Tuesday THROUGH Friday)...

The strong upper level ridge that will bring the heat this
weekend into early next week will be flattening and pushing back
east during the extended period. This will help temperatures to
return to near average for the time of year. It will also bring
increased onshore flow as we see troughing over the PacNW, overall
winds are not expected to be strong but could be breezy through
the Delta. Westerly flow will dry the mid-levels out and no rain
or thunderstorms are expected during the extended forecast.

-CJM

&&

.AVIATION...
VFR conditions over interior NorCal next 24 hours. Surface winds
generally below 12 kts except vicinity of Delta southwesterly
surface winds up to 20-30 kts.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 9 PM PDT Monday for Burney Basin /
Eastern Shasta County-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-West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.

&&