Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
243 FXUS66 KSTO 300917 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 217 AM PDT Thu May 30 2024 .SYNOPSIS... Elevated fire risk today due to breezy northerly winds and low humidity values. Warming trend continues, with Friday expected to be the warmest day. Slight cooldown Saturday through Monday, then chances increase for triple digit high temperatures through the week. && .DISCUSSION... Upper level troughing continues to move eastward this morning extending into the northern Great Plains, and upper level ridging is building in eastern Pacific. As the trough continues to move eastward, our heights will be orientated in a northwesterly pattern, which will lead to locally breezy conditions and low relative humidity (RH) values today. Strongest northerly winds will once again be in the northern and central Sacramento Valley, along the I-5 corridor with wind speeds of 10-20 mph and gusts up to 30 mph possible. Strongest winds are expected this morning and afternoon, before easing in the early evening hours. Low RH values of 10-20%, combined with the breezy northerly winds will lead to elevated fire weather conditions to exist once again for the Valley today. High temperatures will climb into low to mid 90s for the Valley as well, leading to Moderate HeatRisk for the Valley. On Friday, the upper level ridge moves inland and will lead to an increase in high temperatures around the Valley into the mid to upper 90s, with around a 30-50% chance of breaking 100 for the central and northern Sacramento Valley. Onshore flow should keep the Delta in the low 90s for high temperatures. Widespread Moderate HeatRisk will overtake the northern/western Sacramento Valley, while the Delta will remain in Minor HeatRisk. RH values will still be in the 10-20% range for the Valley, but wind speeds will be lower and west-south winds will overtake the area Friday afternoon. Weak upper level troughing is then progged to move through the PacNW and extend into NorCal on Saturday, which will reduce high temperatures slightly on Saturday and Sunday, with low to mid 90s for the Valley, mid 80s for the Delta, and cooler upper 60s to low 80s for the foothills and mountains. Most of the forecast area will be in Minor HeatRisk, with isolated spots of Moderate HeatRisk, mainly from Yuba City north into Redding. Upper level troughing is then forecast to build in the Gulf of Alaska, and flatten our heights out into a more zonal pattern late Sunday. && .EXTENDED DISCUSSION (Monday THROUGH Thursday)... On Monday, a trough will eject from a closed low in the Gulf of Alaska into Alberta and keep our upper level height pattern in a zonal component. The westerly flow aloft will help cool things down from Sunday`s temperatures, with the Valley being in the upper 80s to low 90s and low 60s to low 80s in the foothills and mountains. Tuesday is when the area will experience a warmup in temperatures, as an upper level ridge is forecast to build over NorCal, increasing the heights and increase our temperatures. Much of the Valley will experience mid to upper 90s Tuesday, with the Delta remaining in the low 90s as the high pressure strengthens. Most of the Valley will be in Moderate HeatRisk on Tuesday, with isolated Major HeatRisk around Chico. Wednesday and Thursday we will continue to see our upper level ridge strengthen over the area, which will continue to allow high temperatures to climb. Wednesday high temperatures are currently forecast to range from the upper 90s to the mid 100s across the Valley, with 70s to low 90s for the higher elevations. National Blend of Models (NBM) probabilities of reaching 100 degrees are currently around 65-95% for the Valley. Overnight recoveries on Tuesday night will be in the low 70s for the northern Sacramento Valley and mid to upper 60s for the central and San Joaquin Valley`s. These high temperatures will also introduce widespread Major HeatRisk across the Valley, mainly for areas north/northeast of I-80. Major HeatRisk affects everyone without effective cooling and/or adequate hydration, so make sure if you are outside for extended periods of time to have hydration and a place to escape the heat. A similar situation regarding heat/temperatures will exist on Thursday, with temperatures expected to be in the upper 90s to mid 100s for the Valley, with the hotter temperatures in the northern Sacramento Valley. Cluster Analysis reveals fairly high confidence in this pattern manifesting, and possibly lasting beyond the extended forecast period. The Climate Prediction Center (CPC) has placed our area under high probabilities (70-80%) of above normal temperatures in the 8-14 Day Temperature Outlook. && .AVIATION... VFR conditions next 24 hours. Areas of northerly surface wind gusts 25 kts in the Sacramento Valley until about 00Z Friday. Lighter winds elsewhere. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$