Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
653 FXUS66 KSTO 240827 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 127 AM PDT Fri May 24 2024 .SYNOPSIS... A brief cool down is expected for today and Saturday, with isolated showers possible this afternoon and evening across the northern Sacramento Valley and northern Sierra. Warmer and drier weather then returns from Sunday into next week, with periodically breezy winds. && .DISCUSSION... As of early this morning, a few high cirrus clouds are evident on GOES-West nighttime satellite imagery, but otherwise quiet weather is ongoing for interior NorCal. Broad upper level troughing is currently influencing the region and will continue to do so through Saturday. This is resulting in the return of onshore flow and will lead to cooler temperatures for today and Saturday. Valley high temperatures today only look to reach the upper 70s to low 80s, with 60s to low 70s at higher elevations. Otherwise, breezy south to west winds are expected through the afternoon and early evening, with strongest winds through the Delta vicinity. An embedded shortwave is also expected to move through the broad troughing later today into Saturday. Current ensemble guidance indicates a slight eastward shift in the trajectory, resulting in overall low impacts for interior NorCal. Still, a few isolated showers cannot be ruled out (10% to 20% chance) for portions of the northern Sacramento Valley and northern Sierra this afternoon and evening as the wave moves within the vicinity. Current probabilities of exceeding 0.10" of rainfall are at 5% or less. With onshore flow persisting and generally low heights aloft, the cooler temperatures from today are expected to linger into Saturday as well. Current forecast high temperatures are firmly in the mid to upper 70s in the Valley and 50s to 60s at higher elevations. While immediate impacts from the shortwave passage are not expected for interior NorCal, it is expected to kick the broad troughing aloft eastward across the late weekend into early next week. This will allow for heights to rise across the western CONUS as ridging aloft builds in on Sunday and Monday. As a result, temperatures warm back to near normal on Sunday (80s in the Valley, 60s to 70s at higher elevations) and slightly above normal (80s to 90s in the Valley, 70s to 80s at higher elevations) for Memorial Day. && .EXTENDED DISCUSSION (Tuesday THROUGH Friday)... While heights aloft look to remain high through next week, the primary ridge axis is expected to remain centered over the Great Basin and Intermountain West. Rather, broad troughing aloft is currently in line to remain the primary influencing feature for interior NorCal. This will keep the overall weather pattern somewhat stagnant at least through midweek, with periodically breezy south to west, onshore flow winds, and slightly above normal temperatures persisting. Cluster analysis then indicates some uncertainty in how the trough/ridge interactions will evolve across the late week period, which in turn is leading to some spread (forecast variance of 5 to 10 degrees) within the late week temperature forecast. Current consensus is leaning toward a warming trend, but there is still around 30% of cluster analysis membership depicting a slight cooling trend. && .AVIATION... VFR conditions next 24 hours. Local southwest surface wind gusts 20-30 kts in the west Delta, areas of southerly wind gusts 15-25 kts develop in the Sacramento Valley and Sierra after 21Z, and northwesterly 15-25 kts develop across the northern San Joaquin Valley by 21Z. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$