March ReCap/Snow & Cold Looming….
Weather is a little boring here to start the week. After some colder weather over the weekend we will have a warmup today and tomorrow as the ridge builds back in briefly. This is the perfect time to sneak in a recap of the March temperatures and precipitation before our storm Thursday/Friday.
Obviously March was both a cold and snowy month. Let’s start with temperatures which I take from the Truckee airport reporting station. March’s average temp was 31.6 degrees which is 4.3 degrees below average. In the past year only December was above average by 0.8 degrees thanks to lots of mild storms.
I have been tracking the monthly temperature departures from average on a graph for over a decade which you can find on the Weather Charts page. This year we have averaged 3.9 degrees below average and 2.8 degrees over the past 3 years. I would attribute that to the PDO (Pacific Decadal Oscillation) possibly going into it’s next 20-30 year cold cycle.
Over the past 3 seasons we have also increased snowfall each season. This is similar to what happened when the PDO reversed in the late 40′s early 50′s. In there we have the famous weak El Nino year of 1951-52. I’m thinking that we stay ENSO neutral through the summer and then go back to weak La Nina next winter.
That would line us up with 56-57 & 74-75. Those were below average precip winters for Northern CA although 74-75 ended up ok for snowfall thanks to fluff from the colder temps. Maybe I’m completey crazy with these analogs and my thinking, but it worked well for my forecast of 125% of average snowfall I had for this season, although we ended up with 142% of average (so far). I’m thinking an average to below-average winter next season right now, and then maybe a big rebound the following season.
Anyway, enough ranting, let’s go over the precip for March. There are 2 basins that are tracked by the NWS, the Tahoe Basin and the Truckee River Basin. The Tahoe Basin is for the South Lake Tahoe areas, and the Truckee River Basin is the North Lake areas down to Reno & Pyramid lake where the river ends.
The Tahoe Basin picked up an average of 11.77 inches of liquid which is 217% of the average for March. The Tahoe Basin has now picked up 92% of the water average for the year and we are only 6 months into the water year. The Truckee River Basin averaged 10.65 inches of liquid which is 226% of average for March. The Truckee River Basin has now picked up 134% of the average for the water year. So basically if we have no precipitation for the next 6 months we still finish at 134% of average for the year!
That is why Governor Jerry Brown declared the California drought over last Wednesday. Southern CA cities will get their full allocation from the Sierra water supply and the farms will get more than their average allocation. We aren’t done with winter yet though so more snow and more liquid is to come, it’s only April 4th.
We have a strongly positive AO (Arctic Oscillation) right now which we have had since February. Normally that keeps the arctic air over the Arctic for the most part, but we have some stratospheric warming going on over the pole right now. That is in the layer of the atmosphere above the surface and when it warms it will displace the cold underneath to the South. That should cause chunks of Actic air to surge South this month. That is why we will have a see-saw of temperatures.
The warmup is brief today and tomorrow as the next shot of cold air is set to move in Wednesday. This shot is much stronger than over the weekend. Highs today could break 60 at lake level and 50 on the mountains. As the cold front approaches on Wednesday winds will pick up and highs will be about 10 degrees colder. Then after the front moves through Wednesday night we have really cold air for April on Thursday and Friday. Highs only in the 20′s on the mountains and 30′s at lake level.
There will be some light snow with the cold front but this is coming down from the North over land again so it is pretty dry. Then the cold core associated with the main low comes down the coast Thursday and Friday. This is a pattern that has been known to bring some bigger snows to the area, but it depends on how far over the water the low tracks as to how much moisture it can pull in. Expecting snow showers most of Thursday and Friday.
Models are back and forth on the liquid amounts and snowfall. Right now it looks like at least several inches up to a foot on the moutains. Even several inches at lake level as it is really cold and snow levels are well below lake level. Will have to watch this closely this week as to the exact amounts of liquid we can pull in. This will be a nice fluffy mid-winter style powder, another amazing treat here late season.
Saturday and Sunday stay cold but about 10 degrees warmer into the 30′s and 40′s as a very brief ridge builds back in. By Monday night we could see another cold front move through with light snow. Models are all over the place long-range but right now it looks fairly unsettled and cool next week with some more shots of snow.
Another brief ridge could build in for the weekend of the 15th before we could have another cold trough the week of the 18th. I’m still waiting to see if we can get the wavelengths to lengthen around mid-month and get some more more moisture with one of these storms. We still have a chance here at one more big storm with these surges of cold if we can get the jetstream a little juice. Stay tuned……BA
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