Big Pattern Change, Spotty Rain for Now

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As News of the North Bay has been reporting, a major change in our weather pattern is coming this week, but while much of California will get its first rain in weeks, that rain will be spotty across the North Bay, at least for now.

By Tuesday, the high pressure that’s dominated our weather for weeks will be replaced by a trough of low pressure.

The trough will bring cooler air, but little rain for now. However, a cut-off low pressure system may tap into moisture to our south and bring rain to parched areas of Southern California and the southern Sierra. Here is the outlook on the Canadian model for rain through this Friday.

As you can see, the rain seems to wrap around the Bay Area and much of Northern California, leaving us with only a few showers. Pretty much the same thing on the European model.

However, another model forecast is a bit more optimistic, showing the chance of one or two tenths of an inch of rain over the North Bay by Friday.

So, not much coming our way this week. But looking into the week of the Nov 25th-Dec 1st, a few models show rain reaching us by the end of the month. Here is the Canadian emsemble forecast, which is an average of many computer generated possibilities.

And the GFS model.

Of course, these forecasts are more than a week out so we have to take them with a grain of salt. Still, there is room for optimism that real rain may arrive in the region by the end of November.

How about December? Well, the long range CFS outlook suggests that starting around the week of December 1st, the chances of average, or above average rainfall for California will increase.

So for now, we’ll have to sit back and see what happens. Cut off low pressure systems like the one expected to spin down the coast of California are very hard to forecast accurately. More showers could come our way, or stay to our south and east. But, for now expect cooler weather with clouds and perhaps some showers by midweek, with the chance of much more rain arriving in the week after Thanksgiving.