The winds are going to be breezy to very strong, off and on through Thursday
After record high temperatures were set Friday in multiple Southern California locations, Red Flag Warnings continue on Saturday. Residents in Santa Clarita can expect the temperature to reach 83 degrees today, with the humidity in the low teens, and 22 mph winds out of the northeast gusting to 33. Strong winds will continue through Saturday night but will taper off a bit Sunday, 18 to 22 mph gusting out of the northeast at 28 to 34.
Monday afternoon a strong offshore pressure gradient will begin growing, bringing very strong winds out of the northeast again, with the humidity in the low 20s and teens.
Wildfire danger described as “very critical” by the National Weather Service is in the forecast for Southern California this week. Strong winds gusting at 55 to 70 mph in the mountains is predicted for Wednesday night and Thursday, which will be followed by warm temperatures and single-digit relative humidities into the weekend.
A Red Flag Warning is in the forecast for San Bernardino Wednesday through Saturday.
The Hot-Dry-Windy Index will be increasing Tuesday through Monday.
Southern California Edison has notified some of their customers that strong Santa Ana winds on Thursday and Friday could result in a preemptive power shutoff on Thanksgiving in order to reduce the chance of wildfires being ignited by power line failures caused by the winds.
The National Weather Service has issued Red Flag Warnings from Ventura County south to San Diego County as well as the Lower Colorado River Valley.
The Red Flag Warning goes into effect at 2 p.m. Thursday about the time many Southern Californians will be thinking about sitting down for Thanksgiving dinner. It will end at 6 p.m. Friday.
The forecasters expect 40 to 55 mph northeast winds in the lower elevations with isolated gusts to 65 mph in the mountains, with 12 to 25 percent relative humidity Thursday dropping to 8 to 15 percent Friday. The wind will decrease during the weekend but it will remain breezy and dry.
The Angeles National Forest will have extra firefighters on duty through this wind event.
Your #ANF firefighters will increase staffing through this fire weather event. Additional resources also moving into our area to boost local firefighting resources.
Hot, dry and in some cases windy weather will bring elevated wildfire danger to many of the western states through the Labor Day weekend.
Extreme heat in southern California could set all-time high temperature records with the possibility of rolling power blackouts and more wildfires. Some of the inland cities could have temperatures 10 to 20 degrees above normal through Monday. The hottest days will be Saturday and Sunday, with slightly lower temperatures Monday. Riverside could see highs of 116 on Saturday and 118 on Sunday.
Red Flag Warnings are in effect Saturday for portions of Riverside and San Diego Counties through Sunday at 6 p.m. Forecasters expect east winds of 15 to 20 mph with gusts of 25 to 35 mph, with single-digit humidities in the afternoons.
A Fire Weather Watch for the Los Angeles, Ventura County, and Santa Barbara mountains for Monday evening through Tuesday evening will probably be turned into a Red Flag Warning for gusty sundowner winds from the north or northeast at 15 to 25 mph with local gusts up to 40 mph Saturday, increasing to 15 to 30 mph with local gusts up to 45 mph Sunday evening and Monday evening. The strongest winds will be in the western portions of the Santa Ynez mountains and Santa Barbara south coast.
The National Weather Service did not mince any words in describing the forecast:
The very hot and unstable conditions will bring a significant threat of large plume dominated fires across the region through Labor Day.
Northwestern United States
A strong high pressure ridge centered across the western Great Basin Saturday will bring continued hot and dry conditions through the afternoon and early evening, with temperatures in the 90s and humidities below 15 percent, contributing to potentially extreme fire behavior given the very dry fuel conditions. In central Idaho and western Montana winds are expected to exceed 20-25 mph for several hours Saturday afternoon.
August 23 through 24, partly due to the possibility of dry lightning
The chance of lightning with little or no rain Sunday and Monday combined with high temperatures and low humidities has led to predictions of elevated fire danger.
Red Flag Warnings are in effect for the northern half of California Sunday and Monday. The highest threat of dry lightning is Sunday afternoon through Monday morning.
Thunderstorms with little or no rain is what started over 500 fires earlier last week. On Monday scattered or isolated dry thunderstorms could hit northern California and portions of Nevada, Utah, Wyoming, and Colorado. The storms are expected to move farther north Monday.
Nick Nauslar, a Fire Meteorologist at the National Interagency Fire Center in Boise wrote about the forecast in a tweet at 11:30 p.m. Saturday, saying, “Hundreds of new fires are likely if this event pans out.”
The Hot Dry Windy Index (HDW) predicts higher than normal fire danger for the area of the Hennessey Fire in the Bay Area Sunday through Tuesday. On Sunday it is above the 90th percentile compared to the average for the date. The HDW is a fairly new tool developed for firefighters to predict weather conditions which can affect the spread of wildfires. It is relatively simple and only considers the atmospheric factors of heat, moisture, and wind. To be more precise, it is a multiplication of the maximum wind speed and maximum vapor pressure deficit (VPD) in the lowest 50 or so millibars in the atmosphere. The HDW only only uses weather information – fuels and topography are not considered by HDW at all. If the fuels are wet or have a high live or dead moisture content it will not be reflected in the data.