textproduct: Sacramento

KEY MESSAGES

- Near to above-normal temperatures and areas of Moderate HeatRisk into next week, with continued onshore flow moderating overnight temperatures.

- Breezy southerly winds and marginally low daytime humidity will bring elevated fire weather conditions today.

- Monsoonal moisture to bring showers and thunderstorms to the Sierra early next week.

DISCUSSION

Mostly clear skies this afternoon across NorCal, accompanied by locally breezy southerly winds in the Sacramento Valley. Weak high pressure to the south and off-shore troughing are continuing to keep upper level heights across NorCal more zonal. Valley & foothill southerly winds and marginally low daytime humidity values are leading to slightly elevated fire weather conditions today. Fire weather conditions will improve as we move into the overnight hours as the main driving factor, the winds, begin to weaken later tonight. The start of the weekend will see high pressure begin to move eastward and into the greater Four Corners region, while amplified troughing remains offshore. Ridge will strengthen by Sunday, allowing for a gradual climb in afternoon high temperatures with areas of Moderate HeatRisk Saturday and Sunday.

Ridge moves further north and east by Sunday, with offshore troughing remaining in place, which will allow for monsoonal moisture surges into the area Sunday through at least the middle of next week. 500mb vorticity suggests several shortwave shots of energy moving onshore Sunday afternoon and evening, potentially tapping into the monsoonal flow to bring mainly cloud coverage and/or virga to the Valley and foothills. More robust moisture surge and upper-level synoptic support arrives late Sunday night/early Monday morning, where slight chances of Valley sprinkles have been introduced to the forecast. Better support for convection will remain in the higher elevations in the Sierra and south of I-80, however precipitation and/or t-storms cannot be ruled out along most of the Sierra Nevada as we push into Monday afternoon and evening.

While confidence has increased in monsoonal moisture surges, enough instability in the area remains the biggest question on t-storm development for lower elevations in the foothills. Forecast soundings do show inverted-v profiles, however lack of instability in the lower levels may prevent convection from developing. Latest NBM runs have introduced slight (15%) chance of thunderstorms to around 3000 feet along the Sierra Monday afternoon and evening. Uncertainty remains high on the lower elevation development, and for that reason we have decided to hold off on any fire weather products at this time.

Monsoonal moisture will continue to push through our higher elevations along the Sierra Tuesday-Thursday, where a roughly 15-30% chance of afternoon/evening thunderstorm will exist, with the best probabilities along and east of the Sierra crest. Best chances will remain mainly south of I-80. With warmer temperatures continuing, fuels will start to dry out, so fire weather concerns will continue Tuesday through Thursday. Widespread Moderate HeatRisk enters the forecast Tuesday and Wednesday, before widespread Minor HeatRisk takes over Thursday with slightly cooler afternoon high temperatures.

AVIATION

VFR conditions prevail across interior NorCal next 24 hours. Surface winds from south to southwest around 15 to 25 kts in the Sacramento Valley. Surface winds around 15 to 20 kts in northern San Joaquin Valley. Gusts everywhere except the Delta decrease to 12 kts or less around 09z Saturday.

STO WATCHES/WARNINGS/ADVISORIES

None.