Dangerous, Multipronged Storm Strafing Central/Northern California
What may become known as the President’s Day Storm of 2017 barreled into the San Francisco Bay area on Monday morning. The core of the storm was an atmospheric river roughly 75 to 100 miles wide, pointing a firehose of moisture toward vulnerable foothills and urban areas. With soils already sodden, the risk of flash flooding was high, and the tail end of the storm promised to bring ferocious winds into the area that could knock out power for many thousands of residents, in some cases for prolonged periods. Toward the Sierra, the storm will deliver yet another onslaught of torrential rain and several feet of mountain snow, as the region’s water infrastructure groans under its fiercest assault in a number of years.
Heavy rain: Location is everything
Monday’s atmospheric river (AR) extends back in a fetch almost directly from Hawaii, as shown in Figure 1, making it a classic “Pineapple Express.” The AR was carrying at least 1.25” to 1.5” of precipitable water, or the amount of moisture in the column of air above a particular spot. That’s an amount seen on average once every 5 to 10 years in the area, noted the Sacramento office of the National Weather Service. Unlike many big storms, this one won’t arrive with a strong surface low; instead, a relatively weak low will be moving into Oregon on Tuesday, well north of the fairly linear AR.
Oriented from west-southwest to east-northeast, the AR will be translating north and south across the southern Bay Area on Monday. The exact timing and duration of those north-south shifts are difficult to predict, but they will largely control where the heaviest rains fall. Since Sunday, models have tamped down the peak storm totals somewhat, and pushed the most likely location of the heaviest rains southward into the South Bay region, roughly from San Mateo to Santa Cruz. Localized amounts could be enormous--potentially 10” or more on the west side of the Santa Cruz Mountains.
The cities of San Francisco, Oakland, and Sacramento will see moderate to heavy rain throughout Monday, most likely totaling 2” to 3”. These amounts could be lower or higher depending on how much time the AR spends on the northern edge of its north-south range. Pockets of urban flash flooding are a given, but the bigger impact in these cities could be the high winds expected to rip through the area later on Monday, toward the tail end of the storm (see Figure 3). With the soils so wet, these winds could easily knock large trees onto power lines. If these outages are especially widespread, it may take days for repairs to be completed.
https://www.wunderground.com/blog/JeffMasters/dangerous-multipronged-storm-strafing-centralnorthern-california
ack ack ack ack ack !!!!
Stay dry folks and if they are telling you to evacuate, get the hell out!
Picture in downtown Sacramento, California, January 1862.
= new reply since forum marked as read
in the far north.
Was rattling the rooftops last night. Heavy rain and winds ongoing and raining now with no end in sight!
Be careful is right!
