Evolution of Winter

Here is an incredible gif showing simulated (model-produced) cloud top heights beginning 4am this morning (Thursday) and ending 4pm Saturday. (From the 3km high-resolution NAMX model). The greens represent high, cold clouds (likely raining), the blues represent warmer, lower clouds (possibly also raining, or just low stratus) and the gray/white are either very low clouds or no clouds.


A few features pop out:

1. You can very clearly see the evolution of today's "cut-off" low spinning right over San Diego as it pulls northeastward toward the Rockies. Follow this low with your eyes as it moves eastward across the US...

2. By forecast hour 12 you can see what's known as "frontogenesis" occurring along the front-range of the Rockies. This is, in essence, a new stacked low pressure forming in the lee of the Rockies. Its signature is "lumpy looking" high clouds forming from SW to NE in a frontal band signature.

3. As this low pulls into the Central US by Hour 22 (2am Pacific Time on Friday morning) a very clear sector of warm-frontal precipitation outrunning the surface low has spread into the upper-Midwest region. This precipitation is VERY LIKELY to be dangerous freezing rain. This is because the warm sector of this new storm is likely to have a layer of warm air directly above the surface which should melt whatever snow falls. The melted "rain" will likely enter a tiny, narrow pocket of cold air right at the surface and freeze on contact or very near contact with the ground.

4. As this storm spreads over the Midwest bringing freezing rain, and then, probably, just rain, to Chicago, it should dump some decent snow over portions of the upper Midwest (Wisconsin and Minnesota) before pulling northeastward and "filling it" ;) As this happens...

5. ....a new storm begins pounding the West Coast. By hour 26 (6am Friday morning) a strong front has already moved into the Bay Area. This front will pull northward of LA but is rapidly followed by a more deeply "digging" front evident in Hour 40 (8pm Friday night). What we call "jet enhancement" of the front is clearly visible as this front pulls directly overhead the LA area (dark blues and light greens during Hour 41-43). This should bring a pretty significant rainstorm to the Southland (1-2" of rain).

6. By this time, the first storm has pulled into and out of the Northeast bringing what will probably be a pretty strong rainstorm to the Eastern Seaboard.

Confused yet? :)

Mika ToscaComment