Critical fire weather conditions with widespread moderate heat risk through mid-week

Periods of breezy north winds and low humidity will result in critical fire weather conditions through mid-week, especially through Tuesday. Moderate heat risk through the middle of this week with temperatures peaking Wednesday. Cooler weather returns later this week. Red Flag Warning in effect from 11 AM this morning through Wednesday morning (just extended.)

Discussion

A few high clouds continue to spill over the building ridge over the eastern Pacific into NorCal. North and east surface pressure gradients have tightened a bit compared to 24 hours ago and local gusts of 15-25 mph are present around the periphery of the northern Sacramento Valley.

Current temperatures vary from the mid to upper 50s across most of the Central Valley, to the mid 60s to lower 70s across the north end of the valley where northerly breezes have picked up. A hot, dry and breezy pattern will persist across the region through mid-week as the eastern Pacific ridge moves onshore. Overall, surface gradients likely won’t be quite as strong as last week’s event with the MFR-SAC gradient topping out around 10-12 mbs tonight before gradually tapering by Wednesday.

Northerly gusts of 25-35 mph will be common in the Sacramento Valley into midday Tuesday, and combined with single digit minimum RH will result in critical fire weather conditions (Red Flag Warning goes into effect later this morning).

Temperatures will also continue to trend up into mid-week with widespread moderate heat risk (with locally high heat risk) expected across the valley on Tuesday and Wednesday as highs approach record levels.

Overnight low will also be quite mild, especially Tuesday night when valley lows will only be in the mid 60s to mid 70s. A Heat Advisory has been issued.

Ensembles show the ridge shifting east after mid-week allowing a combination of synoptic cooling and onshore flow to bring relief to interior NorCal.

Extended Discussion (Friday through Monday)

Short wave trough brushes across far northern portions of CA Friday bringing a slight chance of showers to the Shasta mountains. Remainder of CWA can expect some cooling with increased onshore flow. Zonal flow Saturday with some model differences on depth of next wave Sunday. NBM keeps the forecast dry Sunday although EC showing some precip. Models similar in building high pressure inland Monday.