It’s not often that the entire country will get to enjoy the forces of the same system, but that’s what we are looking at right now. As of this moment, the feature is a weak, cold air system bringing snow to the northern Rockies and Pacific Northwest. Radar imagery is less than stellar in this part of the world, so let’s instead take a look the advisories that are out from the Weather Service for the snow.
The system at this moment is fairly disorganized aloft and at the surface. It will get some structural definition as the surface trough dips past the Rockies tomorrow night. We’ll see a closed low developing, which will initiate the drawing of warm air north and cold air south. There is a bit of disorganized warm advection leading to some scattered showers north of the Gulf of Mexico tomorrow night.
The upper level trough will lurk west of the Rockies at this point, essentially handicapping the ability for the feature to take on much moisture initially. Things will change very quickly on Tuesday and especially Wednesday, as the storm moves eastward. Here is what the model has in place on Wednesday, with the strong system tapping into all the available moisture.
As you can tell, the feature will have deepened dramatically from tomorrow evening by mid day Wednesday, and started bringing about some serious precipitation to a good deal of the eastern third of the country. You might note that I haven’t been talking about snow since this storm breached the Rockies. That is because we won’t remember this as a snow storm. Note those red isohypses running all the way up to the Canadian Maritimes. This will be a severe weather event. The SPC is looking at Tuesday and Wednesday for severe weather.
There is a bit of a difference in model guidance at this point. The NAM foresees a secondary low developing in the Lower Ohio Valley, at the base of the upper level trough, before continuing northeast towards New England. This would likely shift the onus of severe weather a shade to the north, and prolong the threat for severe weather later into the night and day.
Stay tuned, as this will certainly be the top weather story this week.