12/23/2025
Edgar McGregor’s forecast for this week’s storm:
MONDAY NIGHT STORM UPDATE:
I am reducing forecast precipitation totals slightly to reflect the better agreement among forecast models on this storm system.
About 5.00” - 9.00” is expected across our foothill communities, with isolated amounts to 14.00” in the mountains. The Weather Prediction Center (WPC) has issued a HIGH-RISK outlook for excessive rainfall across our area, with heavy to torrential rainfall rates.
Wednesday will be a dramatic day for Southern California, with a slow-moving atmospheric river targeting Ventura and Los Angeles Counties. For a full 13 hours between 11 PM Tuesday and noon Wednesday, the central moisture axis will be pointed right at the San Gabriel Mountains. dBZ values above 50 are possible at any time, indicating there is ample opportunity for debris flows in our local burned canyons.
Thursday, however, now appears more dangerous. Sometime around 5 PM, a squall line will sweep the Los Angeles Basin, with extreme rain rates exceeding 65 dBZ. Should a thunderstorm strike a burned canyon, a significant debris flow will be generated, potentially severely damaging unburned homes.
ALL RESIDENTS IN AND BELOW BURNED CANYONS NEED TO SPEND TOMORROW TAKING ACTION TO PROTECT LIFE AND PROPERTY. THIS DOES NOT NEED TO BE A LIFE-THREATENING SITUATION.