HMT Forecast Discussion made at 1945z Sunday 10 Feb 2008
Outlook little changed from yesterday ...
Weak wave passing over northern CA at the moment has only bands of Cirrus with it.
The stronger wave for Tu-W 12-13 Feb is presently associated with a deep surface low S of Cold Bay AK, and a prominent upper-tropospheric short-wave trough feature in water-vapor imagery near 35N/170W. Progs all indicate this latter feature moving ENE through the mean ridge position offshore and then splitting as it approaches the coast of BC and the Northwest, with the southern portion heading southeastward over the ARB late Tu and W, cutting off over AZ by early Th 14 Feb, much as was suggested yesterday. The outlook for pcpn over the ARB with this is no better than it was yda--the best one can hope for is nil to an inch or 2 of dry snow over the higher ridges of the Sierra. The dividing streamline (between coast-parallel southerly flow to the N and northerly flow to the S) along the W coast is forecast to remain near or N of the OR-CA border as this weather system approaches the coast Tu, and consequently little or no pcpn can be expected, even along the north coast.
Farther ahead, the outlook remains grim for more pcpn. (My cousin who farms a section near Clements on the Mokelumne River reports that the ground is saturated at his place.) The GFS ensembles frm 00Z 10 Feb indicate with unanimity that the ARB will remain dry through 12Z Tu 19 Feb. This morning's 12z GRS ensembles extend this streak to 12Z W 20 Feb! Beyond this, indications are of overall larger amplitude and the possibility of more pcpn in northern CA, but there is no clear consensus for a significant event, just indication that the probabilities increase to climatological for the date by late next week.