Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
414 FXUS66 KSTO 302122 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 222 PM PDT Thu May 30 2024 .SYNOPSIS... Elevated fire risk this afternoon due to breezy northerly winds and low humidity values. Warming trend continues, with Friday expected to be the warmest day this week. Slight cooldown Saturday through Monday, then chances increase for triple digit high temperatures by mid-week. && .DISCUSSION... Discussion at a Glance - There is a 40-60% chance of Sacramento Valley climbing into the triple digits on Friday, followed by a slight cool down Saturday-Monday and increased onshore flow. - A significant heat event is expected Wednesday & Thursday bringing Major HeatRisk for the Valley & Foothills and a high likelihood (70-95%) for widespread triple digit high temperatures in the Valley. - Prepare for elevated daytime highs & overnight lows Wednesday & Thursday and reconsider outdoor activities during the hottest part of the day (3:00-7:00 pm). SHORT TERM DISCUSSION Taking a peak outside the window (and looking at GOES- West visible imagery) it`s another sunny day with a few high clouds across interior Northern California. North winds continue to gust 20-25 mph through the Sacramento Valley where peak gusts today reached 25-35 mph (30mph+ gusts closer to Redding & Red Bluff). Relative humidity (RH) values remain in the teens & low 20s across the Valley this afternoon. As we head into the evening, winds will weaken through the Valley and a weak Delta breeze kicks in later this evening as humidity values increase especially around the central Sacramento and northern San Joaquin Valleys. On Friday, temperatures will increase as an upper level ridge moves inland with Valley highs in the mid- upper 90s, with approximately a 40-60% chance of exceeding 100 for portions of the central and northern Sacramento Valley. Onshore flow will help keep the Delta in the low 90s for high temperatures and aid in overnight recovery (cooler temperatures and higher humidity values). 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. More pronounced Delta breeze is expected in the evening hours with gusts 15-25 mph through the Delta & Sacramento Metro Area. A brief "cool down" (highs in the low to mid 90s for the Valley, mid 80s for the Delta, and cooler upper 60s to low 80s for the foothills and mountains) is in store for this weekend as a weak upper level trough moves eastward. Most of the forecast area will be in Minor HeatRisk on Saturday & Sunday, 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. //Forrest && .EXTENDED DISCUSSION (Monday THROUGH Thursday)... Zonal flow aloft will lead to slight cooling on Monday, with Valley temperatures in the mid to upper 80s and low 60s to low 80s in the foothills. Ensembles and cluster analysis reveal an amplifying upper level ridge pattern over the area next week, bringing the potential for a significant heat event. The EFI continues to highlight anomalous maximum and minimum temperatures during this timeframe. Guidance is good agreement that this pattern may last beyond the extended forecast period. By Tuesday, daytime temperatures in the Valley are expected to be in the upper 90s to around 100, with areas of Major HeatRisk in the Central Sacramento Valley. NBM probabilities of reaching 100 degrees are currently around 40-65% for the Valley on Tuesday. There is a high likelihood (70-95% probability) of seeing widespread triple digits in the Valley Wednesday-Thursday, with Valley highs potentially climbing into the 100-1007 degree range. Limited overnight relief is expected with lows in the mid 60s to mid 70s, mainly across the northern/central Sacramento Valley and foothills. Therefore, widespread Major HeatRisk is expected across most of the Valley and foothills Wednesday and Thursday. Major HeatRisk affects everyone without effective cooling and/or adequate hydration. Consider canceling outdoor activities during the heat of the day. && .AVIATION... VFR conditions expected over the next 24 hours. North winds gusting up to 25 kts through the northern Sacramento Valley through 00Z Friday. Sustained surface winds under 12 kts everywhere else. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$