No Extended Very Cold Spells Yet, but Not as Dull as Some Might ThinkDecember 5th, 2012 at 9:59 pm by Don Paul under 4 Warn Weather
Examining computer output here on the evening of December 5th, there are still no signs of a protracted truly cold pattern in the Great Lakes or the east. That is not to say the weather will remain as snowless as it has been. Of course, climatology tells you that much. But actual current data tells more. In the near term, both the 18z GFS and the latest Canadian GEM (far from my favorite model, the GEM) are showing rapid deepening of a low pressure system by Monday, with more snow potential than is seen in the Euro–which also has not been consistent in the east in recent days. The GFS would bring the potential for a cold deformation zone reaching WNY by late Monday/Monday evening, which would allow accumulating snow with strong winds. This would be followed by weaker lake snow on Tuesday, with much less potential. What’s most supportive of this operational run is the 18z GFS 500mb Ensemble Mean, which shows a sharp height fall coinciding with this rapid near-bombogenesis, and stronger cold advection to go with it. The operational GEM also has tremendous deepening of this low at about the same time. FAR from a high confidence forecast, but definitely worth watching.
Other items: Lake Erie is 2 degrees above average today, at 44 degrees. And, the GFS Ensemble Mean is showing stronger Greenland blocking developing in the next week than we’ve seen. Before winter fans get too excited, the Pacific ridge–despite the Greenland block–stays too far west (with no +PNA) for consistently lowering heights in the Great Lakes. But the blocking may allow the NAO to take more frequent dives. Pardon the cliche: Stay tuned.