Cold start to the new year

January 1, 2019 – Areas of gusty northerly winds continue today. Dry conditions are expected through the remainder of the week with cold overnight temperatures and near normal daytime highs. Next chance of precipitation exists this weekend.

Discussion

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Little change to the morning forecast package as the upper low dips into the desert southwest while high pressure nudges in from the eastern Pacific. Breezy winds are expected today, but they will likely remain below wind advisory criteria this afternoon.

Ridge axis shifts inland Wednesday as pressure gradients weaken. Little change in the synoptic pattern Thursday with upper ridging sitting over NorCal. Daytime max temps continue near normal with chilly overnight lows. The next chance for rain arrives this weekend.

Extended Discussion (Saturday through Tuesday)

A pattern change will unfold this weekend with daily precipitation chances likely returning to the forecast after a week and a half of drier weather. The past few model runs of the GFS and ECMWF bring a potent upper low toward the northwestern California coast on Saturday morning. This is a marked northward trend in the GFS with yesterday’s runs favoring a storm track toward Southern California.

Based on this latest suite of guidance, expect rainfall to spread across the region early Saturday morning with accumulating snows over the Sierra/Southern Cascades. There should be a brief lull in the precipitation as a transient shortwave ridge moves through Sunday morning.

In its wake, the pattern across the Eastern Pacific becomes further conducive for additional storm threats to Northern California. Recent guidance has been bouncing around considerably so confidence is low beyond the forecast for Saturday.

However, models have continued to hint at a deeper trough impacting the weather early next week. In addition to the increasing chances for precipitation Saturday onward, gusty winds over the Sierra are likely given tight gradients accompanying each trough passage.

All and all, much can change but the period spanning January 5-8 should prove to be intermittently wet. This is consistent with the above average precipitation probabilities advertised by the Climate Prediction Center in their Day 6-10 outlook.