Cold Air continues to be damned up over the Great Basin and the beginnings of the warm advection snowfall pattern is now occurring in Mammoth Lakes. The snowfall will be light today but should become heavier  Sunday and into that night. 

The new 12z WRF model analysis shows the  HT 500mb  531dm upper low west of the OR/Ca border at 132West……with a diffluent pattern over Calif as it merges with the existing ridge along the CA/NV border. This is truly a warm advection snowfall pattern for the Northern and Central Sierra today as moisture is being lifted by the cold air already in place.  There is no dynamics in play today! The Dweebs love to see other lifting mechanism’s in play!

The models drop this upper low southeast reaching near the Central Ca coast by this evening. Although there is no big moisture plume….the system will have good mid level dynamics with the front left exit region favoring a strengthening lower level onshore flow. Coastal areas of Ca will get some good rains today and with the upper low slowly moving further into Central Ca Sunday, heavier precipitation will penetrate further into the state with the sierra under the gun for some heavy snowfall Sunday afternoon and into the night.  The upper low seems to stall over Ca Monday through Tuesday of next week.  So some light additional accumulations expected. 1 to 2 feet of snow is possible between today and Monday night over the higher elevations.

Longer Range:    



Going into the next 10days…the Models continue to show a future of tremendous high latitude blocking in the jet stream across Greenland and into Northeastern Canada…..and this blocking is pushing into the Arctic circle. Once again…this becomes the powerful negative phase North Atlantic oscillation (NAO) but also forces the Arctic Oscillation (AO) to drop to very low levels similar to last year…but unlike last year during the El Nino, we had the help of the enhanced southern jet…this year the blocking associated withLa Nina will have more profound effects, possibly once again,  with the reestablishment of the blocking high west of Hawaii, and another tropical low to its south.

This mornings ECMWF is continuing the trend to a wetter pattern for California toward the 8th-10th time frame. Mean heights are in the upper 550 and low 560s so it would be wet.  The pattern is simular to the December 18 pattern but not exact.  The American model the GFS so far doesn’t seem to have  much of a clue….so confidence is not as high as it could be.

In using the ensemble means of the ECMWF the past few days….  Once again a strong blocking high develops over Greenland and builds NW toward north Central Canada. This is similar to what happened during mid December, 2010. The NAO goes quite negative.  As Anomalously high heights develop and become cut off over north central Canada, (strong -AO) strong blocking also develops between Hawaii and the Dateline…so,  not as far west as Mid-Dec.  The big polar vortex over the NW Atlantic is suppressed SSE of its normal position and a new Gulf of AK Vortex is in its Development stages. The central pacific block still has the signature of the REX and two distinct jets emerge out of the central pacific and take aim toward the west coast. This would once again be a very wet pattern for parts of Ca.

Because the GFS has not caught on yet…..this is not as exciting a development as it could be, with confidence this far out only marginal……however, given the winter so far and the tendency for patterns to repeat themselves…….the Dweebs will be keeping a weary eye on the situation this coming week!  Again…there is the “Possibility” of another subtropical connection for California developing about the 8th to 10th of January. The ECMWF has the lead.

( Note) This is an outlook…not a forecast! 


Dr Howard and the Dweebs……………………….:-)

Reference Glossary of Weather Terms
Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.