Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
927 FXUS66 KSTO 200800 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 100 AM PDT Thu Jun 20 2024 .SYNOPSIS... Dry weather continues, with a warming trend into the weekend. Temperatures peak on Saturday, with widespread triple digit highs in the Central Valley and into the lower foothills. A little less hot early next week. && Key Points - Above normal temperatures today, much warmer Friday into the weekend, hottest on Saturday. - Widespread Moderate HeatRisk is expected from Friday through Monday -A Heat Advisory is in effect from 11 am to 8 pm Saturday with Widespread Moderate HeatRisk and areas of Major HeatRisk in the Central Valley and foothills on Saturday; Highs in the triple digits. Short-Term Discussion (Today THROUGH Sunday)... Ensembles and clusters indicate that weak upper level trough will remain over NorCal today. This trough will weaken and gradually transition into a ridge Friday into the weekend, as an upper high strengthens over the Desert Southwest. This will have temperatures warming to slightly above normal today in the 90`s, before heating up to well above normal levels from the upper 90`s to low 100`s Friday. Widespread triple digit heat is expected Saturday with Central Valley and lower foothill highs 100-106. Some Delta air will modify the late afternoon high temperatures over the Delta, and portions of the southern Sacramento Valley keeping most of these areas in moderate heat risk versus major to the north and over the foothills. Increasing southwest flow is expected over NorCal Sunday, as a trough moves through the Pacific Northwest. This will likely initiate an afternoon Delta breeze with high temps a few degrees cooler in the upper 90`s and low 100`s. Widespread Moderate HeatRisk is expected to start Friday and will continue through the weekend, with areas of Major HeatRisk on Saturday. Currently probabilities of Sacramento Valley locations (north of Sacramento metropolitan area) reaching at least 100 degrees on Friday are 50 to 90%, on Saturday 75 to 95%. From the Sacramento metropolitan area and southward into the northern San Joaquin Valley, chances are 15 to 50% probability Friday, 75 to 85% on Saturday. Outside of the Delta, winds will generally be light, helping to reduce critical fire weather conditions a bit, despite lowering relative humidity Friday and especially Saturday. && .EXTENDED DISCUSSION (Monday THROUGH Thursday)... Desert SW upper high extends over NorCal Monday into Tuesday with above normal temperatures continuing. Highs in the Central Valley expected in the 90s to around 100 in the warmest spots. Ridge weakens Wednesday into Thursday as short wave trough pushes into the PacNW. Minor synoptic cooling with increased onshore will result. Highs midweek expected in the low to mid 90s for the Central Valley with mainly 70s to 80s for mountains and foothills. Dry weather persists through the extended forecast period. && .AVIATION... VFR conditions over interior NorCal next 24 hrs. Sfc wind mainly below 12 kts except vcnty of Delta SWly sfc wind 15-25 kts. && .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. && $$