textproduct: Sacramento

KEY MESSAGES

- Seasonable to below normal temperatures persist through the weekend and into next week.

- Elevated Fire Weather conditions from dry and breezy weather north of Interstate 80 and isolated mountain thunderstorms in the Sierra south of Interstate 80 through this evening.

- Shower and isolated thunderstorm chances continue south of Interstate 80 today, with drier weather through at least early next week.

- There is high uncertainty in exact details, but unsettled weather and precipitation chances look to return by late next week.

DISCUSSION

Today...

A quick peek at satellite shows troughing largely centered offshore of the Bay Area early this afternoon. This is allowing a rather deep plume of subtropical moisture to filter across interior NorCal today as evidenced by a persistent cloud shield spanning from Stanislaus County up through Shasta County. As a result, high temperatures today are expected to end up around 10 degrees cooler than Thursday. Breezy onshore winds do look to increase through the afternoon with strongest gusts 20-30 mph anticipated in the northern Sacramento Valley/Burney Basin/northeast Foothills. Despite the influx of moisture aloft, daytime humidity values in the teens to lower 20s in the above areas, in conjunction with the breezy winds, will continue to introduce Elevated Fire Weather conditions through this evening.

With the moisture plume and more notable forcing from the offshore trough centered further southward, light showers and virga are being observed generally along a line from Interstate 80 southward. This is expected to remain the case throughout the day, although some areal expansion toward the Highway 36 corridor is possible this afternoon. Even with the moisture rich environment aloft, persistent cloud cover is limiting diurnal heating and available instability with thunderstorm chances looking to become increasingly confined to higher elevations today. Resultant probabilities of thunderstorm development remain around 20-40% along the Sierra south of I-80. As for accumulating rainfall, Valley/foothills probabilities sit around 10-20% for 0.01" with probabilities for greater than 0.25" around 40-70% along the Sierra.

This Weekend Into Next Week...

As the moisture plume pushes eastward heading into the weekend, a trend toward drier weather is anticipated area wide Sunday into early next week. While chances are expected to be notably lower on Saturday, there may be enough overlap of lingering moisture and troughing aloft for additional shower/thunderstorm potential along the Sierra south of Highway 50. At this time, probabilities of showers and isolated thunderstorms sit around 10%, although highest potential will likely be from the Sierra crest eastward. Despite the broader drying trend that is on track late weekend into early next week, the presence of a troughing aloft and low heights will keep temperatures seasonable through the weekend.

By early next week, ensemble guidance is in general agreement on a longwave trough deepening offshore of the Pac NW toward NorCal. The immediate impacts of this developing pattern look to be even further cooling to widespread below normal temperatures and highs in the 70s to 80s for much of the week. There is some potential for early morning low temperatures nearing the freezing mark above 7000 feet by midweek as well. Periods of breezy onshore winds will likely accompany the cool down around Monday-Tuesday, with gusts 25-35 mph possible at times through the Valley and Delta. There continues to be notable ensemble uncertainty on the potential for a return to unsettled and active weather later next week. While additional chances for precipitation remain possible, the timing and location of attendant moisture complicates the forecast at this time.

AVIATION

Active weather continues across interior NorCal today with -SHRA and isolated thunderstorm chances from Interstate 80 southward through 03z Saturday. Despite this, VFR conditions are expected to prevail, although reductions to brief MVFR conditions will be possible in any thunderstorms that develop. Otherwise breezy to gusty south to west winds are expected through 03z Saturday, with strongest gusts 20 to 25 kts in the northern Sacramento Valley and surrounding terrain as well as through the Delta.

STO WATCHES/WARNINGS/ADVISORIES

None.