Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
467 FXUS66 KSTO 252209 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 309 PM PDT Sat May 25 2024 .SYNOPSIS... Temperatures warm back up to near to slightly above normal with areas of minor HeatRisk from Sunday into the week ahead. Lighter onshore flow looks to persist through midweek before dry, northerly flow with lower humidity returns for the late week period. && .DISCUSSION... There was an impressive marine layer intrusion through the Delta and the Central Valley this morning, with low stratus spreading as far north as Redding. This brought breezy onshore winds, with the low clouds persisting into the early afternoon in some areas. With the cool and cloudy start to the morning, afternoon temperatures in the those areas are relatively cool. As a result, Valley high temperatures look to remain firmly in the 70s, with 50s to 60s at higher elevations. The onshore flow pattern is expected to continue but will weaken overnight, with lighter winds into Sunday. The marine layer has mixed out and is much more shallow, so not expecting an influx of low clouds for early Sunday. High pressure ridging builds in Sunday with a strong warming and drying trend beginning. High temperatures for Sunday afternoon rise to near normal for this time of year, with Valley high temperatures in the mid to upper 80s and 60s to mid 70s at higher elevations. The upper level ridge axis is expected to strengthen but will remain centered to the east over the Rocky Mountains. This along with trough developing over the Pacific Northwest limit cooling and continue some lighter onshore flow into mid week. High temperatures for Memorial Day look to reach the upper 80s to low 90s in the Valley and 70s to low 80s at higher elevations, with slightly cooler values forecast on Tuesday. && .EXTENDED DISCUSSION (Wednesday THROUGH Saturday)... Overall, warm, dry, and breezy conditions are expected to prevail through the extended period. There is some forecast uncertainty in temperatures, though, with a roughly 10 degree variance in current forecast high temperatures. Some notable uncertainty is remains in the forecast across the mid to late week period. Latest cluster analysis is leaning toward (~60% of ensemble membership) a solution of ridging aloft building in through the late week period, while still nonzero membership (~40%) indicates a continuation of broad troughing aloft. While the overall differences would be somewhat subtle, the former solution would result in dry northerly surface flow returning and temperatures warming through the end of the week. In contrast, the latter solution would yield a more or less stagnant weather pattern with onshore flow persisting and temperatures remaining slightly above normal. && && .AVIATION... Mainly VFR conditions next 24 hours, except for local MVFR ceilings across portions of the Delta and Valley lingering through the afternoon hours. Winds generally less than 10 kts through 23Z Saturday, then local southwest wind gusts 15-25 kts in the Delta and Sacramento Valley, and west- northwesterly 15-25 kts across the northern San Joaquin Valley. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$