Storm updates (Thurs morning)
Weather Spotters should self-activate all day today, Thurs Feb 13, through Friday afternoon.
Hazardous Weather Conditions
- Flood Watch until February 15, 10:00 PM PST
- Wind Advisory until February 14, 10:00 AM PST
- Flood Advisory until February 13, 01:00 PM PST
All the ingredients are present for a major rain and wind storm. The graphic below from the WPC shows 3-5+ rainfall totals over the entire Bay Area region through 10am PST.
From MTR AFD:
.SYNOPSIS... Issued at 1205 AM PST Thu Feb 13 2025 The atmospheric river has arrived! Major impacts are expected through the day as the moderate to heavy rain continues, winds increase, and thunderstorm chances arrive. The biggest risk is localized flooding and damaging winds, especially through the first half of the day. Conditions will improve Friday. Some light rain is expected in the North Bay on Sunday, but overall the pattern will dry out over the next week. && .SHORT TERM... (Today and tonight) Issued at 1205 AM PST Thu Feb 13 2025 KEY POINTS * Flood Watch in effect 10 PM Wed to 10 PM Sat (area-wide) * High Wind Warning (coastal) and Wind Advisory (inland) in effect from 10 PM Wed to 10 AM Fri (coastal) * Widespread shallow landslides possible Thursday morning * Downed trees and power outages likely * Highest impact areas include Santa Cruz Mtns and Big Sur Coast * High Surf Warning in effect 3 PM Thu to 3 AM Sat METEOROLOGY: We are in the middle of an atmospheric river, driven by a storm force low pressure system off the coast of far northern California. The associated warm front is moving ashore as I type this. Despite the fact that it`s 1230 AM, it`s currently 61 degrees in Monterey. That`s the warmest it`s been in a week. As the warm front moves through and the cold front approaches over the next couple hours, rain intensity will increase to around 1.0-1.5" per hour along the coastal mountains, and roughly half that in the valleys. These high rain rates will cause localized flooding and likely trigger some shallow landslides. The wind speed is also increasing, with current gusts of 30-50 mph observed in higher terrain, and 20-40 mph along the coast. Winds are expected to increase over the next several hours as the cold front approaches. High resolution guidance is still developing a SW`rly 50-60 kt low-level jet at 850 mb from around 2 AM through noon. With the high rain rates, these winds should have no trouble mixing down to the surface at times, and widespread gusts of 40-50 mph are expected across the area, with 60-70 mph possible along the coast and higher elevations. The cold front is expected to move through around sunrise, ushering a colder and drier air mass. The PWAT will drop from around 1.2" to 0.8", while the 500 mb temperature will drop from around freezing to -10F. While the drier air will cause the total rainfall to slowly taper off, individual showers will strengthen as the cold upper air decreases the stability and allows convection to become the primary precipitation mode. This threat is highest from late morning through late afternoon. The Storm Prediction Center continues to show the risk for thunderstorms throughout the cwa today. IMPACTS: Heavy rain is expected to continue for several hours. Minor flooding impacts are ongoing across the majority of the cwa. We have not seen any flash flooding yet, but that risk still exist through the morning for urban areas. Strong wind gusts combined with saturated soils will likely lead to downed trees and power outages. Numerous flood advisories are in effect, and the flood watch continues through 10 PM Saturday as the rivers absorb the run-off. A High Wind Warning is in effect for coastal areas, with a Wind Advisory in effect for inland areas, both through 10 AM Friday. We will likely see notable rises on many major rivers, and the Russian River at Guerneville and the San Lorenzo River have the highest chances of going into flood stage. The San Lorenzo is of particular concern given the rain so far, and how flashy that basin is. The river gauge is already reporting a sharp rise. Other coastal areas outside of the Santa Cruz Mtns may not see the same degree of shallow landsliding, but nonetheless will still have impacts due to downed trees and powerlines, especially areas near the Marin headlands, Big Sur/Carmel coast, and Monterey Peninsula. The commute this morning will undoubtedly be nasty and downright dangerous in some cases (thinking Hwy 17 in particular). When all is said and done, the North Bay will likely end up with 2 to 4 inches, and the Bay Area will see a range of 1.5 to 3 inches depending on if you`re in the South Bay rain shadow or not. The Santa Cruz Mtns and Big Sur coast will be the winners with 4 to 7 inches, locally up to 8-10. Despite some locations seeing some of the lower end of rainfall amounts, wind is still expected to pose a threat to life and property through the day. && .LONG TERM... (Friday through Wednesday) Issued at 1205 AM PST Thu Feb 13 2025 Showers taper off Friday and the sun will even come out in the afternoon. Saturday will start cold with mid-30s inland and mid-40s along the coast. Saturday will stay dry before a much weaker disturbance moves through on Sunday. We are only expecting light rain from this, mainly confined to the North Bay. Otherwise next week looks dry and mild. Long range guidance is somewhat split, but the majority of solutions point to a much drier second half of February as our roller-coaster rainy season continues. &&
