Friday, November 13, 2015

November 17-19 Potential Winter Storm

There is the potential for a winter storm in the November 17-19 timeframe.

Analysis of absolute vorticity values across the Northern Hemisphere shows a pretty active environment, especially with the energy lifting north from the United States into Canada which brought us the strong low pressure system this past week. The main item we want to look at is the piece of energy circled in red in the northeast Pacific, currently moving into the Gulf of Alaska. It is this energy that will provide the chance for this winter storm next week.

The 42 hour forecast from the GFS shows the energy deepening and digging southward into California by Sunday morning. Ahead of the system ejecting into the Plains, we will see a blast of warm air into the Central US, as the trough digs south and forces warm air to advect north over the prairie.

Instant Weather Maps
The real fun starts on the 17th, when model guidance indicates this storm system will eject east into the Plains in the form of a sub-1000mb low pressure system. Here, we see cold air wrapping into the Rockies, and a deformation zone across Colorado and far western Nebraska. It is here where we should see the highest accumulations, should this storm transpire. It is also worth noting the potential for serious flooding in eastern Texas, the Arkansas/Oklahoma border, Missouri, and parts of Illinois.

Instant Weather Maps
Forecasted accumulations range from 6-12" in the western portion of Nebraska, to as high as 48" along the Nebraska/Wyoming border. Colorado could see amounts in excess of four feet, especially if orographic lifting comes into play. The gradient will be sharp in Nebraska and Colorado, and snow ratios should be rather low, given this is an early-season storm.

To summarize:

- A potential winter storm could drop significant snow in Nebraska and Colorado between November 17-19.
- Serious flooding could arise along the Mississippi River due to heavy rains.