Heat lingers into Saturday, elevated fire weather conditions for valley today and early next week – YubaNet

Warm up again today with a cool Sunday. A good chance of showers and thunderstorms on Sunday in the northern areas, followed by breezy northerly winds early next week. Excessive Heat Advisory from 11:00 a.m. this morning through 11:00 p.m. Saturday for Carquinez Sound and delta, central Sacramento Valley, mountains, southwestern Shasta County to western Colusa County, Northeast Foothills, Sacramento Valley, Northern Sacramento Valley, Northern San Joaquin Valley, and Southern Sacramento Valley. Heat advisory from 11am this morning to 11pm Saturday for Motherlode.


The upper level ridge will continue to widen today in the four corners region and this will bring another hot day to NorCal. Yesterday many Valley locations posted highs around 100, today we will add another 2 to 7 degrees to that with 100 widespread for the Valley, 90 in the foothills and 70 and 80 in the mountains.

A moderate to high heat risk is expected today and you should take heat precautions if you have outdoor activities planned. We will continue to see high clouds pass throughout the day as short waves pass to our north over the PacNW.

Today will be the peak of the heat event as the ridge will begin to push east on Saturday as a trough in the Gulf of Alaska begins to push east. This will bring some cooling on Saturday, but it still looks like another hot day with highs near 100 in the lower elevations.

Tonight’s overnight lows are mild, generally 4 to 12 degrees warmer than this time last night. Friday night’s lows will be mild once again, helping to increase the elevated risk of heat. The northerly flow develops today and this will help bring a period of afternoon elevated fire weather conditions to the Valley.

The northerly flow will switch to land on Saturday afternoon and we will see the return of the Delta Breeze, this will alleviate some of the heat in the Delta regions, but not until tonight.

The rear of the depression in the Gulf of Alaska will excavate over the Pacific and reach CA on Sunday. This will bring much cooler conditions with highs up to 20 degrees cooler than today.

It will also bring a chance of showers and thunderstorms to the northern mountains and the northern Sacramento Valley. The cold front will approach the region late on Saturday and some light showers will be possible over the Shasta County mountains later in the day. Rain chances will continue to spread across northern areas overnight as the front moves south and east.

At lower elevations it will take a while for the profiles to saturate and this will limit showers there, but some light showers at sunrise will be possible. The axis of the trough will push through the northern portion of the area through Sunday and this will keep showers in the forecast.

We see instability building over the northern mountains and northern Sacramento Valley in the afternoon. This will bring a chance for some afternoon thunderstorms. Soundings show plenty of shear and some more organized thunderstorms are not out of the question.

Breezy winds, small hail, and short, heavy showers will be the main threat with any thunderstorm. The timing of the front and cloud cover will be a factor in how much instability we will see in the afternoon along with what the environment will look like. Moisture with this channel and front is quite impressive for this time of year with PWAT above 1.0″, but drier lows will limit some of the QPF.

Most of the rain accumulation will be over the northern mountains with a possible light accumulation in the northern Sacramento Valley. The upper level trough will push east Sunday night and any shower or storm activity will end shortly after sunset.

Dry conditions return Monday as ridges begin to form. With the trough to the east, we will see some northerly winds develop in the afternoon. They don’t seem too strong, but 20 to 30 mph gusts seem possible mostly over the Sacramento Valley. This should be enough to bring a period of elevated fire weather conditions.

Extended Discussion (Tuesday-Friday)

High pressure builds inland for the first half of the new week with warmer temperatures and some north to east wind gusts. This could lead to a potential for increased fire weather concerns, depending on how much rain gets wet on Sunday. The warming peaks Wednesday as the associated upper ridge shifts across NorCal’s interior. Increased onshore flow Thursday through Friday with some cooling as an unusually deep Pacific trough approaches.

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