We saw three systems move through in September bringing a coating up to a few inches each. We have transitioned into a more typical fall pattern this week with cool/dry weather. That could continue at least until mid-October.
There is a trough moving through the Pacific NW today that will bring some gusty winds and keep cool air in place into Friday. Highs in the 50's with mostly sunny skies. Over the weekend high pressure builds in over CA and we warm into the 60's which is average for this time of year. Average highs don't drop into the 50's until the last week of October.
There is another trough moving into the Pacific NW by the middle of next week which could cool us down a few degrees, but highs at lake level should remain in the 60's, with 50's in the mountains.
The dry weather may continue at least until mid-month. Storms continue to move through the Pacific NW but stay to our north until then. Some long-range models show storms possibly a bit farther south around mid-month. We will keep an eye on that.
For now, the forecasts keep us fairly dry over the next 2 weeks with a chance for light precipitation around mid-month.
Then we may see high pressure build back in the 3rd week of October for more dry weather.
The Winter Season:
As you may have seen already from major weather outlets, most of the winter forecasts show a drier than average pattern for CA. I will be working on my analog forecast this month, but I have been hesitant to jump on the dry bandwagon just yet. One reason is that all of the forecasts were wrong last year in showing a dry CA, the other reason is that the sea surface temperatures are still changing.
The warm water off the west coast has been cooling in recent weeks, and the water along the equator that was below average with a La Nina signal has been warming. The CFSv2 forecast has changed over the last 2 months from a forecast for weak La Nina, to ENSO neutral, and now has us bouncing back to weak El Nino similar to last winter.
So we can continue to wait and see how things settle out this fall to get a better idea of how the oceans may affect the pattern this upcoming winter season. Accuweather just released their winter forecast on 10/2 and it is more favorable for CA showing more of an El Nino type pattern.
A lot of people ask about the correlation between early snow in September and the rest of the season. There really isn't any correlation, but there is a bit more of a correlation with October snow. These are just historical statistics and have nothing to do with the historical patterns versus the forecast patterns for this season that will drive the weather pattern. They are fun to look at though!
I don't have the final numbers from the Snow Lab for September yet, but I'm assuming they saw at least a couple of inches for the month. Here are all the Septembers since 1970 that saw measurable snowfall at the Central Sierra Snow Lab, and the snowfall for the following month of October as well as the total season snowfall.
The thing that should stand out is that every year with measurable snowfall in September also saw measurable snowfall in October. So if we don't see any measurable snowfall this month it would be an anomaly. We have had 12 Octobers without measurable snowfall in the past 50 years, about once every 4 years.
For the season, 7 of 12 seasons saw below-average snowfall following a September with measurable snowfall. The average for all the seasons put together is around 101% of average snowfall.
For October we average 10 inches of snow over the past 50 years. Here is a look at the last 10 years. We had no measurable snowfall last October, so we are due statistically.
So just looking at the stats, with having no October snowfall once every four years on average and always seeing measurable snowfall after a September with measurable snowfall, we should statistically see measurable snowfall this October. As I said, this is just based on historical numbers, not based on the forecast pattern for this October.
Looking at the forecast for the month of October on the CFSv2 it shows below-average precipitation...
...and near average temperatures.
It only takes one storm to drop measurable snowfall. We will keep an eye on mid-month and beyond. Until then, enjoy the nice fall weather!
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