Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
338 FXUS66 KSTO 040925 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 225 AM PDT Tue Jun 4 2024 .SYNOPSIS... Elevated fire weather concerns today coupled with well above normal temperatures. Periods of moderate to major HeatRisk is anticipated today through the end of the week. Cooler, but still seasonably warm, weather by the weekend. && .DISCUSSION... Heat Event Key Points - An Excessive Heat Warning goes into effect at 11 am today, lasting through Thursday evening across the Valley and adjacent foothills. - Areas of Major HeatRisk today for the Valley, become widespread Wednesday for the Valley & Foothills with widespread triple digit high temperatures. Expect elevated daytime highs and overnight lows and reconsider outdoor activities during the hottest part of the day (3:00-7:00 PM). - Areas of Major HeatRisk continue on Thursday, with Moderate HeatRisk by Friday; Triple digits in the Northern and Central Sacramento Valley and adjacent Valley foothills with mid to upper 90s in the Delta and Sacramento metro area. Short-Term Discussion (Today THROUGH Friday)... Valley temperatures are in the mid 60s to low 70s early this morning (as of 1:30 am) as upper level clouds combined with rising heights aloft work to trap warmer air closer to the surface. Temperatures will only increase as today marks the first in a string of days with generously above-normal high temperatures. Upper- level ridging will continue to build today over Northern California along with rising heights aloft across the western CONUS. Accompanying the elevated temperatures will be periods of gusty northerly surface winds today-Wednesday. These winds combined with low minimum relative humidity values in the Valley (15-20%) will lead to elevated fire weather concerns today. Current forecast high temperatures have the Valley and foothills firmly in the 90s to triple digits today through Thursday and limited nighttime recovery with overnight low temperatures in the mid 60s to low 70s. This will result in generally widespread Major HeatRisk in the Valley and foothills from Tuesday through Thursday. While comparatively not as hot, mountain high temperatures still look to reach the 80s to 90s with attendant widespread Moderate HeatRisk from Tuesday through Thursday. Current probabilities of exceeding 100F in the Valley are around 50% to 80% today, 85% to 95% on Wednesday, and 75% to 95% on Thursday. As a result, an Excessive Heat Warning goes into effect at 11 am PDT this morning, for much of the Valley and foothills. Additionally, periods of gusty north-northwesterly winds are expected today throughout the Valley. Strongest winds are anticipated through the central and southern Sacramento Valley and northern San Joaquin Valley, where gusts of 20 to 30 mph will be possible at times. This dry northerly component to the wind will also lead to afternoon minimum relative humidity values into the upper teens to low 20s. As a result, elevated fire weather conditions are expected in the Valley today. Winds will lessen by Wednesday, followed by periodically breezy onshore flow returning on Thursday and Friday. By the time Friday comes around, high temperatures will slowly begin to recover namely in the Delta where highs will be in the 80s with Minor HeatRisk. Elsewhere across interior NorCal, temperatures will cool slightly heading into the weekend, but remain above-normal for this time of year. Area waterways continue to run fast and cold from snowmelt, creating dangerous conditions for those seeking relief in rivers and lakes next week. Remember to practice heat and cold water safety this week! To view the latest HeatRisk, please visit www.wpc.ncep.noaa.gov/heatrisk/ To view current water temperatures, please visit www.cnrfc.noaa.gov && .EXTENDED DISCUSSION (Saturday THROUGH Tuesday)... Upper trough in EPAC weakens as it progress through NorCal over the weekend. Associated onshore flow will help to taper the heat with 90s expected through much of the Central Valley. EPAC ridge then builds into NorCal early next week resulting in a return of triple digit heat to much of the Central Valley with 80s to 90s for the mountains and foothills. && .AVIATION... VFR conditions over interior NorCal next 24 hrs. In Central Vly/Delta NWly sfc wind up to 20 kts with lcl gusts to 25 kts possible thru 02z Wed, otherwise wind mainly at or below 12 kts. In foothills/mtns lcl N-E sfc wind up to 20 kts with gusts to 30 kts. && .STO WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning from 11 AM this morning to 8 PM PDT Thursday for Carquinez Strait and Delta-Central Sacramento Valley-Motherlode-Mountains Southwestern Shasta County to Western Colusa County-Northeast Foothills/Sacramento Valley- Northern Sacramento Valley-Northern San Joaquin Valley-Shasta Lake Area / Northern Shasta County-Southern Sacramento Valley. && $$