Slow Retrogression of the Eastern Pacific High to begin this weekend with the first of the inside sliders to effect the high country in the form of cooler breezy weather Sunday….
Friday December 7, 2012
Posted at 6:57 am by Howard
Over the next two weeks, a pattern of slow retrogression of the eastern pacific high will take place allowing short wave Trofs to begin their march into the CONUS from the Pacific Northwest about Midnight tonight. The 140 knot upper jet slices diagonally through the state of Washington as it become more north/south orientated with time eventually pointing its energy over northern NV as a 160knot jet. This initiates significant cooling over the Great Basin some of which backs up over the eastern sierra giving us from 5 to 7 degrees of cooling from today’s predicted high of 51. A continuation of slow retrogression builds the eastern pacific high from about 135 to 140 west to 145 to 150west but is not as amplified by Wednesday the 13th/14th.
So the 1st short wave “of interest” may bring a little snow to the high country about Tuesday night/Wednesday. The ECMWF has about .25 of an inch over the crest. So a few inches of snow is possible at this time. Its trajectory looks too much over land and the position of its upper jet is not as favorable for our area. Another little shot of snow rolls though about Friday night the 14th. It as well does not have a favorable upper jet trajectory for our area.
At this time it is the Sunday of the 16th that begins a series of short waves (Storms), with improving over water trajectory for the Sierra. The Sunday/Monday system may dump a foot or better for our high country. Further retrogression will set the stage for even better snow producing storms about the 18th/19th.
As we move past the Winter Solstice and toward the end of the year….the inter-seasonal models are indicating above normal precipitation. Based upon the long range 500HPA height field from the CPC, some of these storms could be Major Snow producers especially between Christmas and New Years…..
The forecast for this weekend and through Monday is for fair weather through Saturday with breezy conditions developing Sunday in town. Stronger winds northerly winds are expected Sunday “over the crest” 60MPH. It will be sensibly cooler Sunday.
Next update Monday…………….
Dr Howard and the Dweebs…………………………..:-)