Wednesday, March 2, 2016

California To Get Needed Big Dump Of Rain, But Too Much At Once?

NOAA's maps indicate the possibility of more than eight
inches of rain over the next seven days in parts of northern
California, Oregon and Washington.  
California was banking on a blockbuster stormy winter this year, and a hoped-for cooperative El Nino to dump lots of winter rain and snowstorms on the state to at least ease the crippling drought there.

Things were going OK, not supendous, but OK through January with fairly decent amounts of rain and snow.

That made the intense drought ease a little, but didn't come close to actually ending the drought. Everyone knew an incredible amount of precipitation would have to fall to do that.

Then February hit. It turned brutally dry again, enough to set off a few out of season brush fires. And it turned hot. Record hot.

So warm that some of the snow in the Sierra Nevada mountains melted. You don't want it to melt yet. It should melt later in spring and summer, when the water from that snow can feed parched brooks and rivers.

Now California is hoping for a wet March. That hope might jusy turn into reality. Signs point to a change in the weather pattern that would dump boatloads of precipitation on California over the next couple of weeks at least.

That's great news, but it comes with a price. So much rain might fall in such a short period of time that some of that needed water would run off quickly in the form of dangerous, life threatening floods.

It's too soon to get into the specifics on precisely which days the heaviest storms might hit California and how bad they might be.

But a few computer models suggest as much as 20 inches of rain during the montho of March on parts of northern California and as much as 25 feet of snow in the Sierra Nevada.

That's the upper extreme, of course. It might not be that bad. The hyped 25 feet of snow in the Sierra Nevada would be a good thing. Oh sure, it would cause temporary, immense problems with travel through the mountains. A few structures might collapse, which would be bad. And where do you put 25 feet of snow if you have to get it off your driveway.

Still, one or two dozen feet of snow in the California mountains would be immensely helpful for water supplies this summer.

The heavy rain is more complicated. On the one hand, some of the runoff from the anticipated storms would get stored behind dams in reservoirs.

But jeez, a foot or more of rain in some spots over the course of a couple weeks? Cue the floods and mudslides.

The initial waves of storms don't look too bad. Weak ones today and Friday in northern California will drop light rain and snow there, and pretty much nothing in southern California.

Stronger storms over the weekend will be heavier, but won't be extreme, especially given the dry conditions left over from February.

But we'll have to watch this pattern, as we could get a few rounds of incredibly torrential precipitation in California into the middle or even end of the month.  It's a wet pattern, but figuring out if it's going to be merely wet or inundating is premature right now.

The heavy rain pattern will extend north into Oregon and Washington as well.

On the other extreme, southern California in particular could miss out on some of the rain. Some uncertain preliminary signs hint at a rainy ten day stretch in southern California followed by drier conditions. But such long range forecasts are unreliable. I'm just putting that out there as a possibility.

If you don't live in or near California, but elsewhere in the United States, this change in the weather pattern affects you. Yes, you.

The storms in or near southern California would eventually eject out into the Plains States. If they go far enough north from there, and are strong enough, the have the potential to cause outbreaks of severe weather and tornadoes.

It's too soon to declare how widespread or how bad any bursts of severe weather would be anywhere from the Plains to the East Coast, but it is worth watching as the storms begin to parade across the nation next week.

The changing weather pattern also favors warmth in the eastern half of the nation, so if you're pining for spring, or spring weather is already embracing where you are, this is good news for you.

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