Below is a map of 500mb. The blue circle shows where the close off is and H5 (the black circle inside the blue circle).
Soooo quick info about how the upper layers work. I wrote this before in here:
For reference anything with h/H in it is designating height in mb. For example, h925 is 925 mb where as h85/7/5 is 850mb/700mb/ and 500mb respectively.
The governing physics of weather is such that the upper levels (h925 and above) are what govern sensible weather (ie what precip falls, how much, winds, etc).
For winds, you want to look at h925. The winds here are what can mix down. Normally you take a 10-15% reduction, however, that is not always a hard and fast rule.
For precip type, a good rule of thumb is to look at h85 and h925. If h85 is below freezing, there's a good chance the precip is frozen, and likely snow (there are exceptions when there are warm pockets above h85). If it is above freezing, it is likely liquid. Now if h85 is above freezing and h925 is close to freezing or below, there is a good chance you are looking at freezing rain. If h85 and h925 are above freezing, most likely it is plain rain. The exception here is if you have a very shallow yet very cold surface layer and/or the ground has been frozen for a good period of time (ie a cold spell for a few days) and sfc temps are just at or very slightly above freezing. Usually lighter precip helps to aid this exception as well.
For precip rates, you want to look at H7. H7 will show you where the model thinks the best forcing is going to be as well as the available energy for precip. H7 is about frontogenic forcing.
Lastly, let's look at H5. I won't go into h3/250 as that is beyond the scope of this post. So for H5, this is where you look for phases and energies moving across the continent. So, the 0z GFS slipped east about 75 miles. If you just look at that, well.. Then to you all hope is lost. Yet if you look up at H5, you see that one of the energies phased slightly early, causing a slightly late capture of another energy, ie, phasing late. This allowed the surface low pressure to slip east. However, when you look through the energies at H5, you quickly begin to realize that a less than 3 hour difference in any one of the energies - and consequential phasing - would have changed the outcome (Ala 6z Euro). I'm not going to go too deep into H5 energies as if you have been following along, you would have seen this explained before. If you have not been, follow along from here and look out for what this post has pointed out. To go into h5 energies and orientations would be too long a post and likely confusing as each phase and energy act differently depending on location, speed, strength, etc. It's best to just observe for this moving foreward.
One last thing regarding upper levels. For a coastal storm (or in the Midwest when a storm explodes and runs up from the gulf), you want to be NW of the various closing off of lows at the upper levels. When low pressure systems develop, they develop from SE (at the sfc) to NW (through H5). This diagonal development with regard to height in the atmosphere allows each low pressure center at each level to vent (ie expel air up and outward so that the pressure can fall. Remember, in layman's terms, pressure is essentially a measure of how much air is in any given space at any given time). So as you always want to be NW of the sfc low pressure for frozen precip, you want to be NW of H85 for snow and NW of H7 for the best snowfall rates. When H7 moves directly over or West your area, this is when you can dry slot and when h85 moves over or west of your area, you have h85 temps which shoot above freezing and this changes your snow to other types of precip (remember we talked about upper levels temps earlier).
On H5/7/85 maps, when a LP closes off a this level, it is represented through a close black contour (ie circle)
These are just some general rules to keep in mind with these types of storms and why the surface depictions on models are really the laziest type of forecasting and produces poor forecasting skills and verification.
It is also why I am not writing this storm off at all.
Last note - the Euro with its resolution tends to pick up on these rules the best. This is why it used to be the gold standard.
