An autumn mini heat wave that should make for a toasty Thanksgiving and has already delivered a pair of record high temperatures to the San Diego area is expected to intensify and peak Wednesday, according to the National Weather Service.
The unseasonable heat began Tuesday, with the Miramar area and Montgomery Field both reaching 89 degrees. Lindbergh Field reached 78.
Thermometer readings topped out Tuesday at 73 in the Palomar Mountain area, exceeding the prior Nov. 21 milestone of 72, set in 1962; and 85 in Campo, topping the old high mark of 82, logged in 1995.
While Tuesday saw a big jump in temperatures — most areas were about five to 15 degrees above what they'd been just 24 hours earlier — Wednesday is expected to be the warmest day of the late-season heat wave. Temperatures should be about the same as Wednesday or just a few degrees cooler on Thanksgiving.
"Record highs are likely just about anywhere from the coast to the deserts on Wednesday and Thursday," the NWS said. "Weak offshore flow and the associated down-slope warming will send valley temperatures soaring into the mid-90s. It's quite likely that temperatures here in Southern California will be the highest in the land."
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High temperatures Wednesday are forecast to be 15 degrees above average in the deserts and about 25 degrees above average west of the mountains, including 85 to 90 degrees near the beaches, 93 to 98 inland, 94 to 99 in the western valleys, 86 to 91 near the foothills, 77 to 86 in the mountains and 87 to 92 in the desert.
On top of the hot, dry conditions Wednesday and on the heels of the record-breaking heat wave that parched vegetation in October, the United States Forest Service is also forecasting Santa Ana winds Wednesday that could drive a late-season wildfire. The Forest Service's Santa Ana Wildfire Threat Index, which categorizes Santa Ana winds based on anticipated fire potential, says that given existing conditions in the county, "upon ignition, fires may grow rapidly."
"Easterly winds of 15 to 25 mph along with higher gusts can be expected across the San Diego Mountains," according to the threat index. "Humidity will be in the single digits. Fuels are very dry and will support high rates of spread should an ignition occur."
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While the Santa Ana-driven wildfire threat will be only marginal on Wednesday, there is little precedent for Santa Ana fire potential this late in November.
Mostly clear skies are expected both Wednesday and Thursday. The ridge of high pressure causing the hot, dry weather will begin to break down Friday and the weather will begin to slowly cool over the weekend, though above-average temperatures are forecast through at least Sunday.
