Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
398 FXUS66 KSTO 102109 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 209 PM PDT Mon Jun 10 2024 .SYNOPSIS... A significant heat-up is expected early this week. Major HeatRisk and widespread 100s will develop across the foothills and Valley by Tuesday and continuing into Wednesday. Temperatures will trend cooler late in the week. && .DISCUSSION... Key Points - An Excessive Heat Warning for areas north of I-80 remains in effect from Tuesday morning through Wednesday evening with areas of Major HeatRisk and widespread triple digit highs Tuesday afternoon. - A Heat Advisory for areas south of I-80 is in effect from Tuesday morning though Wednesday evening with widespread Moderate HeatRisk and areas of Major HeatRisk. - Local waterways are still running cold and fast from snowmelt Short-Term Discussion (Today THROUGH Thursday)... Very little changes to the forecast as ensembles still on track. Tonight and Tuesday...as has been exptected for a while with both GFS and ECMWF Ensembles....some riding builds into northern California tonight between deep upper low in Gulf of Alaska and a weak closed upper low off coast of southern California. Major HeatRisk values covering most of northern california with slightly lower values south of I80 and the current highlights look good. Wednesday heights start to fall as we get more under the influence of the Gulf of Alaska low pressure system. This will bring good onshore flow wednesday afternoon and keep temperatures down a bit south of I80. We may be able to expire the Heat Advisory south of I80 but will keep it out for now. Ensembles and clusters in good agreement that we will get more westerly flow and lower heights and HeatRisk values fall to moderate most area. To view the latest HeatRisk, please visit www.wpc.ncep.noaa.gov/heatrisk/ Area waterways continue to run fast and cold from snowmelt, creating dangerous conditions for those seeking relief in rivers and lakes. To view current water temperatures, please visit www.cnrfc.noaa.gov && .EXTENDED DISCUSSION (Friday THROUGH Monday)... Friday into the weekend the large Gulf of Alaska low will continue to impact the area. This will result in cooler temperatures and possibly some wind starting to work into the forecast...especially north and west parts of the valley. This may result in some elevated fire conditions which we will look closer at tomorrow as confidence increases for possibly messaging. Rasch && .AVIATION... VFR conditions over interior NorCal for the next 24 hrs. Surface winds mainly below 12 kts except in the vicinity of the Delta which could have southwesterly wind up to 20 kts at times tonight. && .STO WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning from 11 AM Tuesday to 8 PM PDT Wednesday for Central Sacramento Valley-Mountains Southwestern Shasta County to Western Colusa County-Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-Shasta Lake Area / Northern Shasta County. Heat Advisory from 11 AM Tuesday to 8 PM PDT Wednesday for Carquinez Strait and Delta-Motherlode-Northern San Joaquin Valley-Southern Sacramento Valley. && $$