What I find most interesting is how the frontal intensity varies diurnally. I'll concentrate on the NAM model forecast of 12-h accumulated precipitation, 850-mb temperature (850-mb is roughly the elevation of the basins and valleys of the Intermountain West), and surface wind from 1200 UTC 15 March (0600 MDT this morning).
By this afternoon (0000 UTC 16 March), the Pacific cold front has been shredded and lacks a well organized structure. There is simply an area of precipitation and cold advection penetrating into western Nevada.
|1200 UTC 15 March NAM precipitation (color fill), 850-hPa temperature |
(red contours), and 10-m wind forecast valid 0000 UTC 16 March
|Same as above except valid 1200 UTC 16 March.|
|Same as above except valid 0000 UTC 17 March.|
The importance of daytime frontal sharpening is, however, underscored by the evolution over the subsequent 24-hours. In particular, note how the front weakens by Thursday morning and then strengthens again by Thursday afternoon.
|Same as above except valid 1200 UTC 17 March.|
|Same as above except valid 0000 UTC 18 March.|