Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
311 FXUS66 KSTO 202150 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 250 PM PDT Thu Jun 20 2024 .SYNOPSIS... Dry weather continues, with a warming trend over the next couple of days resulting in Moderate HeatRisk Friday-Monday. Hottest temperatures of the week will be on Saturday with widespread triple digits. After Saturday, there will be slow cooling trend to start next week, but temperature will remain above normal. && Key Points: - Widespread Moderate HeatRisk is expected from Friday through Monday, with areas of Major HeatRisk Friday-Saturday - Onshore flow will promote good overnight humidity recovery, minimizing fire weather concerns this weekend. - A Heat Advisory is in effect from 11 am to 8 pm Saturday with Widespread Moderate HeatRisk and areas of Major HeatRisk in the Valley and foothills on Saturday; Highs in the triple digits. Short-Term Discussion (Today THROUGH Sunday)... Clear skies with a few passing mid- to high level clouds are being observed across Northern California this afternoon via GOES- West Visible Imagery. An upper level trough will start to break down as we transition to a ridging pattern by Friday. As a result, a warming trend will continue today, peaking on Saturday with widespread Moderate HeatRisk expected Friday through Monday, with areas of Major HeatRisk Friday and Saturday mainly over the Sierra foothills & northern Sacramento Valley. The National Blend of Models (NBM) is indicating a 80-100% chance of temperatures greater than 100 degrees F throughout most of the Valley on Saturday. While daytime relative humidities will be in the teens and 20s, weak onshore flow will allow overnight relative humidities ranging from 50-80 percent with the highest percentages in the Vicinity Delta. This onshore flow pattern will minimize significant fire weather concerns during this upcoming period of elevated high temperatures and keep high temperatures cooler around the Delta on Saturday. By Sunday, a trough is expected to move through the Pacific Northwest resulting in increased southwesterly flow. This will translate into a more robust Delta breeze on Sunday with gusts 15-25 mph through the Valley. Slightly cooler temperatures will follow, but Moderate HeatRisk is expected to continue across most of the Valley and foothills through Monday. && .EXTENDED DISCUSSION (Monday THROUGH Thursday)... Moderate HeatRisk continues Monday with slightly cooler temperatures. Clusters and ensembles depict an upper-level high pressure that extends over Northern California Monday through Tuesday which will continue elevated, above-normal high temperatures throughout the Valley. The National Blend of Models (NBM) is indicating 25-65% chance of high temperatures greater than 100 degrees on Wednesday, with the highest probabilities (greater than 50%) in the northern Sacramento Valley. Onshore flow continues through the extended period as a weak trough moves begins to influence the area on Thursday which will work to keep temperatures around the Delta and Sacramento Metro Area a few degrees cooler. && .AVIATION... VFR conditions continue over interior NorCal over the next 24 hours. Surface wind will be mainly below 12 kts except vicinity of Delta, with southwesterly surface wind gusts to 25 kts. Low marine stratus clouds will be limited to the far western Delta 08z-14z. && .STO WATCHES/WARNINGS/ADVISORIES... Heat Advisory from 11 AM to 8 PM PDT Saturday for Central Sacramento Valley-Motherlode-Mountains Southwestern Shasta County to Western Colusa County-Northern Sacramento Valley- Northern San Joaquin Valley-Southern Sacramento Valley. && $$