Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
802 FXUS66 KSTO 182002 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 102 PM PDT Tue Jun 18 2024 .SYNOPSIS... Dry and generally seasonable weather persists through midweek, with slightly higher daytime relative humidities, better overnight recoveries, and a switch to an onshore flow pattern by Wednesday. A warming trend is expected in the late week and into the weekend. && Key Points - Winds will decrease throughout the afternoon today, with onshore flow dominating most of the area starting Wednesday. - Generally seasonable temperatures continue through most of the week, with a gradual warming trend late week into the weekend. - Widespread Moderate HeatRisk is expected from Friday through Sunday, with some Major HeatRisk in the foothills on Saturday. Short-Term Discussion (Today THROUGH Friday)... Winds continue to trend down this afternoon, as the current low pressure system moves out of the area and leaves a broader trough behind it. This broad troughing pattern will bring the return of onshore flow at the surface on Wednesday, with breezy to gusty south to west late day winds. The trough will also keep temperatures near normal for the time of year through Wednesday, with high temperatures in the Valley expected to be in the high 80s to mid 90s, and in the 70s and 80s at higher elevations. While daytime humidities will remain in the teens to 20s in the Valley, overnight recoveries will generally improve due to the onshore flow. Late week, both daytime and overnight temperatures begin a warming trend, with the Valley seeing the likely return of widespread triple digit temperatures by Saturday as a ridge builds over the Great Basin and heights over interior NorCal rise. Widespread Moderate HeatRisk is expected to start Friday and will continue through the weekend. Currently probabilities of Sacramento Valley locations (north of Sacramento metropolitan area) reaching at least 100 degrees on Friday are 50 to 90%. From the Sacramento metropolitan area and southward into the northern San Joaquin Valley, chances are generally lower, at 15 to 50% probability. Temperatures will continue to warm as we move into the weekend. && .EXTENDED DISCUSSION (Saturday THROUGH Tuesday)... Ensemble guidance and cluster analysis indicate hot temperatures on Saturday from rising heights aloft from ridging over the Great Basin. This is resulting in widespread Moderate HeatRisk across the Valley, foothills and mountains on Saturday, with localized Major HeatRisk in some of the foothill locations. The probability of high temperatures of 100 degrees or higher in the Valley on Saturday is 60-90 percent, excluding the Delta where periods of breezy onshore flow will moderate things. Temperatures then decrease slightly on Sunday and into next week as troughing moves into the region. Widespread Moderate HeatRisk continues in the Valley and foothills on Sunday before retreating to mainly Minor for much of the area early next week. && .AVIATION... VFR conditions across interior NorCal for the next 24 hours. In the Valley, decreasing northerly winds, generally less than 12 kts. In the Delta, southwest winds with speeds of 5-15 kts. In the mountains, expect surface winds from the west becoming easterly overnight, generally less than 12 kts but with some gusts up to 15 kts. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$