The upper flow remains split coming off Asia. The upper jet is divided and so is the energy. To weaken the pattern further…..the short waves in the two upper flows are out of phase with each other. For the central west coast, this has the effect of creating smaller/weaker storms with less precipitation. Expect some light snowfall beginning late Thursday PM into the weekend. HPC QPF is just shy of 1/2 inch for our area through Saturday pm. (3 to 6 inches of snow?)

Longer Range:

There are some significant changes coming about during the second week of December (week-2).  A block sets up near the dateline with a negative tilt ridge importing cold arctic air via the Bering Sea into the Gulf of AK. At the present time, the mean long wave trof position is just outside of 140W, suggesting that the upper jet axis will remain to our north…. more over Northern Ca. This normally keeps the Central Sierra in the warm sector most of the time.  However, this time of the year, this could be quite a wet pattern for the Central Sierra with higher snow levels….. 7000 ft to 9,000ft?  With time…the  jet would most likely sag south into the Central Sierra. This pattern change will be the next WX topic over the following two weeks.

Just a Dweeb Observation……….

It sure has been good to see that heights have been moderately high over the Hudson Bay area so far this fall. As a result, SSTA’s are running some .5c to 3.5c in Hudson Bay. The large body of water is still unfrozen.  I believe that this is not due to global warming but due to global weather patterns.

The key height anomaly has been to this point, displaced far enough to the east to keep the wavelength somewhat excessive allowing good progression of the short wave features. Greenland Blocks that have been developing have not lasted long as the upper jet has either broken them down, or have carried off a lot of the cold Arctic air out over the Atlantic!  This is how a wet central west coast winters works best!

The Dweeber………………………:-)

Reference Glossary of Weather Terms